14.1.1 F1_COP   The F1 key selects the Real Time Center-Of-Pressure (COP) option . This option requires at least one force plate.

	F1_Zero_Channels is specifically for the Kistler force plates and requires and additional cable from the computer to the digital input of the charge amplifier. Pressing the F1 key performs the same function as the reset switch on the Kistler amplifier.
	F2_Center is pressed to center the COP (indicated by the white square on the color monitor) on the target. The F2 key should be used prior to data collection to allow for variations in stance, location on the plate, etc. to be taken into account.
	F3_Params is selected to change the current parameters displayed in the upper left and right corners of the menu box. Bandwidth specifies the width of the colored rings displayed on the color monitor. The display becomes more sensitive as the size of the bandwidth (target) decreases. Changing the bandwidth simply scales the size of the target. It has no effect on the values of the collected data. Trace mode can either be turned on or off using the up/down arrow keys. When the trace mode is turned on, the path taken by the COP is displayed by a white trace on the color monitor. When the trace is turned off, no path is displayed. Sound is used for biofeedback with the tone increasing in pitch as the distance from the center of the target to the COP increases. The sound can be turned on or off with the up/down arrow keys. Plate(s) is used to specify one, two, or both plates.
	F10-Done

Pressing any key on the keyboard will begin sampling in the Real-Time-COP mode. When sampling is completed the screen will display a summary of the center of pressure data previously taken. The upper right corner of the menu box displays the total distance that the COP traveled over the plate(s) during the sample period. Each ring of the target is specified and a zone with zone 1 in the center extending out to zone 7 at the edge of the color monitor.

	Time indicates the amount of time the COP was in the specified zone.
	The % sign indicated the percentage of time spent in each zone compared to the total sample time.

Pressing any key on the keyboard will return to the F1-COP menu. F1-Data Analysis will return to the Analog Data Processing Menu. F10-Done will return to the Main Analog Menu.

14.1.2 F2_Scope   The F2 key selects the Real Time Oscilloscope option. This option is useful for examining data as it is being sampled.

	Esc_Abort
	F1_Zero is used to zero the "offset" from the analog channels prior to data sampling..
	F2_Channels key allows the channels to be specified for display on the color monitor. When this option is selected, an additional menu will be displayed to select the desired channels. Select the first and last channel(s) by pressing the up/down arrow keys and pressing ENTER. Up to 7 channels can be displayed simultaneously, however, they must be sequential. Channels can not be skipped in the oscilloscope mode. Pressing F10 returns to the Start Oscilloscope mode.
	F3_Scales allows each of the displayed channels to be scaled to appropriate values for maximum resolution. When this option is chosen, an additional menu will be displayed to set each channel.
	F4_AutoRepeat is a toggle switch that enables continuous sampling (indefinite period) or sampling for the specified period of time. The current status is displayed in the upper corner of the menu box.
	ANYKEY_Begin Press any key on the keyboard to begin Analog sampling.

Pressing any key on the keyboard will initiate data collection in the oscilloscope sampling mode.

When scope sampling is completed, pressing any key on the keyboard will return to the Start Oscilloscope Sampling Menu and ready the system for another sample to be taken. F1-Data Analysis will return to the Analog Data Processing Menu. F10-Done will return to the Main Analog Menu.

14.1.3 F3_Vectors   The F3 key selects the Real Time Force Vectors. This option requires at least one force plate and a video input source and allows vertical force plate vectors to be superimposed on a live video image.

	F1-Mode is a toggle switch for displaying vectors in either a single or multiple mode. The current mode is displayed in the upper left corner of the Real-Time Vector menu.
	F2_Calibrate is selected to calibrate the force plate with the video image on the color monitor. This process involves digitizing the four corners of the force platform. the F1 key should be used to select the camera viewing axis. The current axis is displayed in the upper right corner on the menu box and represents the direction the camera is facing relative to the force platform coordinate system. The camera should be placed perpendicular to any edge of the platform and the appropriate viewing axis selected prior to digitizing the corners of the platform. Digitizing begins with the front-left corner of the plate and proceeds with the rear-left, rear-right, and front-right corners. Left and Right refer to the platform as it appears to the computer operator on the color monitor. Pressing the ESC key aborts the calibration option and returns to the Real-Time Vector menu.
	F3_Params is selected to scale the size of the displayed vectors, set the delay time, set the color for displayed vectors, or adjust the brightness, contrast, color or saturation of the video image. "Max Force" field allows the size of the vector to be scaled to the color monitor. Enter the maximum vertical force expected and press the ENTER key. "Dly(Sec)" is the delay time (in seconds) for capturing the data to a file. The default for this value is 0.033 to correspond to 30 frame/second data capture. The vector color is selected by pressing the up or down arrow key. Press the ENTER key to save the desired color choice. F1-Adjust key allows the adjustment of contrast, brightness, color and saturation image parameters. These are adjusted by using the mouse to drag the box on the line corresponding to the desired image parameter. For auto-digitizing reflective markers, the contrast between the reflective markers and the background should be maximized. Adjust the contrast and brightness to achieve the desired maximum contrast. Pressing the F10_Done key will return to the Real Time Vector Parameter menu.
	F4_Erase is selected to erase the vectors displayed on the color monitor.
	F5_ Restore is selected to restore a file previously saved. The restored image contains the video image as well as superimposed vectors. F1_Open_File is used to retrieve a file from storage. "Advance" is selected to retrieve the next consecutive data record in the current file. The current record number is shown in the upper section of the monochrome display next to "Save#". If there are no additional data records in this file a flashing message will inform you of this fact. After the "Advance" function is performed, the analog module will proceed to the curve display menu for examination of the data retrieved from the files. "BackUp" is selected to retrieve the previous data record in the current file. If there is no previous data record (i.e. the current Save# is 1) a flashing message will appear on the screen. After the "Backup" function is performed, the analog module will proceed to the curve display menu for examination of the data retrieved from the file. "Select" is chosen when you wish to retrieve a data record by number from the current file. Data records are numbered consecutively from 1 in each file and the current record number is shown in the upper section of the monochrome display next to "Save#". The system will ask for the record to be retrieved to be selected from a table of record numbers and IDs that are presented in the menu box. This record will then be read from the data file and the analog module will proceed to the Analog Processing menu for examination of the data.
	F10_Done returns to the Main Analog Menu.

14.1.4 PgDn   The PgDn key is only active for the 32 channel option and allows the user to toggle between the first and second set of 16 channels. When the last set of channels, lower case letters a through p, is displayed PgUp will be displayed.

14.2 SAMPLE   The Sample option is selected to initiate sampling of the analog data channels. The analog input is controlled by the analog sampling parameters that are displayed above the menu box on the monochrome screen. These parameters must be set before the Analog Module may process the analog measurements. Thus, because the Sample option is used to initiate the analog measurements and all other options of the Main Analysis Menu are used to set these sampling parameters and prepare the module for sampling, the Sampling option will be discussed later in Subchapter 14.8, Analog Measurement Process and the other options will be discussed first in the next subchapters.

14.3 PERIOD   Period is selected to set the duration of analog measurement. The sampling period is the length of an analog sample in seconds. All the active analog channels are measured continuously over the sampling period. The number of analog measurements that are performed for each channel during the sampling period is determined by the sampling rate or Rate/Chan. The sampling rate is the number of data measurements per second for each analog channel. The total number of data values sampled and saved is the sampling period times the rate/channel times the number of channels. Thus, if 1000 is entered in Rate/Chan and 2 is entered in Period then 2000 data values are collected for each channel during the sampling period. If there are eight active channels, then a total of 16,000 data values would be collected each time analog sampling is performed. The Analog module can collect a maximum of 32,000 data values at one time. If the sampling period times the sampling rate times the number of channels exceeds 32,000 then the sampling rate (Rate/Chan) will be automatically reduced to stay within the maximum number of data measurements.

When specifying a sampling period, it is best to select a period that is long enough to encompass the entire activity, but not so long as to collect a large number of unnecessary data measurements. Some experimentation may be necessary when setting up for analog data collection to determine the optimum sampling period. In a similar manner, the sampling rate should not be set to a higher value than necessary for the type of signal being measured. The Rate/Chan is set through the Options selection on the Main Menu.

14.4 TRIGGER   The Trigger option is used to set the parameters relating to the triggering event. Triggering is a technique whereby the level of the analog signal being measured is used to determine the start of the sampling period. These include the trigger channel, the trigger level, and the pretrigger percent.

For example, if the measurements of a running stride are being made using a force platform, one could observe the subject approaching the platform, and then manually initiate sampling just before foot contact occurs. Unfortunately, experience has shown this to be an unreliable method of data collection as there is too much chance of starting the measurement too early or too late and thus missing some of the activity being studied. A more reliable method is to use the analog signal from the force platform resulting from the initial foot contact to mark the beginning of the sampling period. This illustrates the concept of a triggering event.

Frequently, one wishes to start analog measurement before the actual triggering event occurs. In the example above, by the time the foot contact signal reaches a level sufficient to trigger analog sampling some of the low level initial contact forces have been missed. A pretrigger analog sampling some of the low level initial contact forces have been missed. A pretrigger is a technique whereby a number of the most recent analog measurements are saved while awaiting the triggering event. This is accomplished using a circular buffer in which the most recent samples replace the oldest ones. When the trigger occurs, measurement continues to the end of the sampling period. then the desired number of pre-trigger measurements are copied from the pretrigger buffer yielding a continuous analog sample starting at some time before and ending at sometime after the triggering event.

The trigger parameters on the Trigger Parameter Screen are:

	Channel# selects the input channel used for triggering. It may be any of the active analog channels shown in the Channel Table. The trigger channel is marked in the channel table by a blinking letter in the CH# column.
	TrigLevel is used to select the signal level on that channel that will cause triggering. The trigger level is entered in the units defined for that channel. Since analog input signals may be positive or negative, this value may also be positive or negative. Triggering will occur at the first measurement on this channel that is at or above the trigger level. Thus the trigger is not used to start actual sampling, but rather to determine when the period of saved values is to start.
	Pre-Trigger% is used to select the percent of the total sampling period that will occur before the triggering event. Pretriggering is accomplished by continuously sampling and saving data values in a circular buffer. That is, only a limited number of samples are saved with new samples replacing the oldest ones. This parameter can be set to any value between 0 (no pretrigger) and 99. It is possible that fewer than the desired number of pretrigger samples may be collected. This occurs when the triggering event is detected after analog input is armed or started, but before the full pretrigger period has elapsed. In this event the sampling period will be shortened by the amount that the pretrigger period is shortened. The pretrigger option allows the trigger level to be set high enough to eliminate false triggering due to noise, while still capturing significant data signals that occur before the trigger.

14.4 FILE   Unless analog measurements are to be immediately processed and then discarded, they must be saved in data files on the system disk or on diskettes. The File option on the Main Analog Menu is used to create, New, or access analog data files, Old, on the current directory. The name of the data file being used by the analog module is shown next to File in the parameter area. If no name is displayed, then no data file is currently accessed, or the current file may be Closed to prevent further access.

In addition, the current data file may be converted to "DIF", "WKS" or "ASCII" format for interchange with other software programs.

Each analog sample, the measurements for one sampling period, is saved in a separate record in the file. As additional samples are saved they are added to the end of the current file. Up to 100 individual samples may be saved in a single analog data file. The number of the current analog file record is shown in the Save# item in the parameter area. Individual data records cannot be deleted without deleting the entire file.

14.5 MODE   Up to this point, the measuring and saving of analog data values have been discussed. This is the initial or default mode of the analog module and is called A/D mode because actual analog to digital conversion is performed. This mode indicator appears in the Input_mode field in the parameter area. To access previously saved analog samples, the input mode must be changed to the File Mode so the analog values will then be read from the desired file. This is done using the Mode option on the Main Analog Menu.

In the File mode, analog sampling cannot be performed using the analog to digital interface. The Sample option on the Main Analog Menu is replaced by the Retrieve option. This option allows previously sampled and saved data to be read or retrieved from a data file. When Retrieve is selected, one may Advance to the next saved sample in the file or Backup to the previous saved sample or Select any particular saved sample. The Select option will display a list of all sample ID's in the file to facilitate sample selection. When a saved sample is read, the information is displayed in the same manner as when analog sampling has been performed. The analog processing menu appears on the monochrome monitor, and analysis of this sample may then take place.

It is possible to change between A/D mode and File mode at any time. For example, if data is being sampled and saved in a file, in the A/D mode, it is possible to review previous samples by selecting File mode and reading the desired sample. Similarly, if previously sampled data is being examined, in the File mode, it is possible to add new data to this file by selecting A/D mode and performing additional sampling of analog signals. New data is always saved at the end of a file so that previously saved data is retained.

14.6 DISPLAY   Display is selected from the Main Analog Menu to either add or remove one of the three plot_lists of the analog channels or change the colors of various items on the color monitor such as curves, axis, logo or background.

14.6.1 Plot_Lists   Plot_lists are merely lists of analog channels that are plotted or graphed together. By grouping channels in this manner, time is saved in the display and analysis of analog input. The first plot_list is automatically graphed after each analog sample is collected or read from a file. The other plot_lists may be graphed by selecting the "2nd" and/or "3rd" options on the analog processing menu. The "Plot" column in the channel table shows which plot list(s) each analog channel is associated with. The three lists are designated by the number 1,2 and 3. A channel may be on more than one plot_list, if desired. since the first plot_list is automatically graphed when analog input is performed, it is recommended that as many of the input channels be assigned to this list as is practical. Channels with different units should be assigned to separate plot_lists, as graphs are labeled with the units of the first channel plotted.

The menu box lists all the analog channels. A channel is selected by simply pressing the letter key for that channel or highlighting the channel letter and pressing ENTER. A channel that is currently selected may be removed from this plot_list by selecting that channel letter again. The plot_list assignments are shown in the channel table at the top of the monochrome screen under the "PLOT" heading. A 1 indicator is used for the first plot_list, and 2 for the second, and a 3 for the third. A channel may be on more than one list at the same time. 14.6.1.1 F1-Multiple Single   A plot_list is normally displayed in "Multiple" mode. In this mode all channels on the list are drawn on a single graph. Alternately, a plot_list may be displayed in "Single" mode. In this mode each channel on the list is displayed on a separate graph. This option is often used for rapidly fluctuating data such as EMG signals. The mode of the current plot_list is shown in the upper right corner of the menu box and may be changed by pressing the F1_Multiple/Single key. Each time F1 is pressed the mode is toggled to the other display mode.

14.6.1.2 F2-Envelope   As an additional option, Automatic Envelope Processing may be selected for a plot_list. When this option is selected (usually when EMG signals are being processed), and envelope curve will be graphed for each data curve on this plot_list. To select this option, press the F2-Envelope key and enter a time constant for the envelope curve. The time constant is shown in the upper left corner of the menu box. A value of "None" indicates that the automatic envelope option is not selected.

14.6.2 Colors   Colors is selected when the color assignment for one or more of the display items is to be changed. Color selection may be performed for each of the data curves (up to nine on a single graph), the graph axes, the logo (text at the top of the display), and the display background. Each item may be set to any of the sixteen available colors. Be aware that items set to the background color will disappear. they may be seen again by setting the color to another value.

	Curves (1st thru 9th) are listed to change the color of one of the data curves used to graph the measured analog signals. Colors are changed by pressing the up/down arrow keys until the desired color is displayed. THE ENTER KEY MUST BE PRESSED TO SAVE CHANGES TO THE COLOR MENU!
	Bgnd is used to change the color of the backgrond display.
	F10-Done is pressed to advance to the second page of color options.
	Axes changes the color of the graph axes that are drawn when data curves are plotted.
	Logo changes the color of the display logo at the top of the color graphic display screen.
	Background changes the color of the display background.

14.7 OPTIONS   Later in the chapter, certain analog parameters used in the sampling mode will be introduced. The Options item on the Main Analog Menu is used to select the Options Menu for specification of these items.

14.7.1 Max_Rate   The Max Rate is used to set the maximum sampling rate for a single analog channel. The maximum rate is used to calculate the actual sampling rate, Rate/Chan that appears in the analog sampling parameters. In most cases, the actual sampling rate will be the Max_Rate value. However, certain conditions will result in a smaller Rate/Chan value being used. The first condition is when the aggregate sampling rate (number of channels times Max_Rate) exceeds the maximum hardware sampling rate (20,000 samples/second with a single channel maximum of 5,000 samples/second) the "Rate/Chan" will be reduced automatically to adjust to the maximum hardware limit. If this latter condition occurs, the Rate/Chan value may be increased by decreasing the sampling period.

14.7.2 Gain Gain is used to set the programmable gain on the analog input module. The current gain is shown in the Gain field in the analog sampling parameters. The initial or default gain is 1 (no signal amplification), which results in an analog input range of + 10 volts and a resolution of approximately 5 millivolts. for low level input signals, the gain may alternately be set to either 10 or 100. A gain of 10 gives an analog input range of + 1 volt, and a resolution of approximately 0.5 millivolts. A gain of 100 gives an analog input range of +100 millivolts and a resolution of approximately 50 microvolts. when a gain of 100 is used, an optional capacitor must be connected to the analog converter to increase settling time. This, in turn, decreases the maximum aggregate sampling rate to 20,000 samples/second. If only higher level analog signals will be processed, the analog module may optionally be equipped with a programmable amplifier having gains of 1, 2, 4 and 8 rather than the above mentioned 1, 10 and 100.

14.7.3 Last_A/D   The Last_A/D field is used to select the number of active analog channels. Since the active channels always begin with channel A, the number of channels are set by specifying the last active channel. The active analog channels appear in the channel table at the top of the screen. The number of entries in this table are determined by the value of the Last_A/D channel. One should not specify more channels than the actual number of analog input signals, as any additional empty channels will waste input buffer space and possibly cause the sampling rate to be reduced.

14.7.4 Auto_Save   Auto_Save is used to specify analog channels that are to be automatically saved to the current data file whenever a new sample is requested. Normally, a Save command must be issued to cause the analog values to be saved in order to prevent unwanted data from being written to the file. In some situations where a number of consecutive analog samples will be measured, automatic saving of data is selected to insure that samples are not inadvertently lost through human error. The current status of the Autosave feature is indicated in the analog sampling parameter area on the monochrome monitor. No indicates that this feature is not selected, while Yes indicates that autosave is selected.

14.7.5 Channels   Channels is used to set or change the individual analog channel definitions in the analog channel table. When this option is selected, a table of the analog channels is displayed. Any channel description (name), units, conversion factor (units/volt of analog signal), and offset (signal level in volts corresponding to zero in the units of that channel) may be entered. The current channel settings are saved each time the analog module is exited so they do not have to be reset the next time the module is run. In addition, each time an existing analog data file is accessed, the channel definitions are copied from that file. In this manner, different sets of channel definitions corresponding to different types of input (force platforms, EMG equipment, etc.) can be quickly accessed from a predefined data set.

The rest of this option discussion has been deferred to the end of this chapter, Sub-Chapter 14.9, Analog Signals and Analog Channel Definition section, to allow the specific features of the analog module to be resented without having to be concerned with the actual source of the analog signals. In practice, the first item to be considered in the data collection process is the source, type, and magnitude of the individual analog signals along with the corresponding definition of the analog channel table.

14.7.6 Plate   Plate is used to define special force platform (force plate) processing by assigning a block of analog input channels to predefined force platform signals. Typical biomechanical force platforms have six to eight analog outputs representing forces and moments measured directly by the platform. These outputs are frequently combined or used to compute additional quantities such as composite forces, moments, and point of application of force. Rather than require a user to set up numerous input channels, the Plate option automatically defines a consecutive group of channels as standard force platform input for the type of platform configured with this system (various platform definitions supporting most commercially available force platforms can be configured when the system is ordered). In addition, since the channel definitions are predefined, the computed quantities are also automatically defined and displayed as additional analog channels.

When Plate is selected the starting channel for the force plate signals must be indicated. The analog module will then show the expected force plate inputs and channel assignments for the type of plate configured to the system. Once configured, all measured and computer force plate quantities are available for graphing and analysis.

14.7.6.1 Info   Info is selected to specify general force plate system information. the information asked for is dependent upon the type of force plate being used.

14.7.6.2 1 Plate   1_Plate is selected to enter parameters for each force plate. the information asked for is dependent upon the type of force plate being used.

14.7.6.3 2 Plate   2_Plate is selected to specify the relative positioning of multiple force plate systems. Additional help is provided at the subsequent data entry form.

14.7.6.4 Electronics   Electronics is selected to enter the force plate amplifier information. the information asked for is dependent upon the type of force plate being used.

14.7.7 Zero   Zero is selected to determine the zero levels for the input channels and the analog-to-digital converter.

14.7.7.1 Channel Range   The Channel_Range is selected to determine zero levels for the analog input channels. the determined zero levels are used by the software to insure that the input analog values are properly zeroed. this option should be periodically executed to insure against zero drift. The analog systems should always be allowed time to warm up before using and zeroing.

Enter the first and last channels for auto-zeroing. Acceptable values are scrolled through using the up and down arrow keys. Typically, all input analog channels are selected including force plate and EMG data. Press ENTER to proceed to the last channel choice. After selecting the last channel, press F10 to return to the previous menu.

Make sure that the channels are at the zero level. For force plates, the zero level corresponds to an unloaded force plate.

14.7.7.2 A/D   The A/D Converter is selected to calibrate the analog to digital converter.

Short circuit the input to the specified channel then strike any key to calibrate the A/D converter. Short circuiting the channel is best accomplished with a BNC shorting plug available from any electronics supplier.

A summary table of A/D values for specific gain settings is displayed for informational purposes. The "New" values have been computed and can be compared to the previous settings listed as "Old" values. A/D values listed as NA for a gain of 2 or greater indicates that the analog board does not have a programmable gain option. Pressing any key on the keyboard will return to the Zero Calibration Function menu.

14.8 ANALOG MEASUREMENT PROCESS (SAMPLE)   Once the analog sampling parameters have been set to accommodate the signals being measured, actual analog sampling may begin. The most recent values of the sampling parameters are saved and are reset when the module is run again. Thus sampling parameters do not need to be set each time analog processing is begun unless sampling values must be changed.

The Sample Option on the Main Analog Menu is used to initiate analog measurement. When Sample is selected, the analog module displays a reminder message to prepare for analog measurement. At this point actual sampling has not begun and two options are available. The first option is to begin analog sampling by pressing any key on the keyboard. The second option is to abort by pressing the F10 key to return to the Main Analog Menu. The purpose of this additional step is to allow a final check of the analog signal source, force platform. EMG equipment, etc., and make sure that the subject is prepared to perform the activity being measured. As soon as analog input is "armed", the analog module begins measuring each of the input signals and monitoring the trigger channel for the triggering event. A message will appear on the screen to indicate that analog sampling is taking place. Sampling may be aborted at this time by pressing any key on the keyboard. The abort option is provided in the event the subject is not able to perform the activity, equipment malfunction, or there is an interruption in the normal sampling process. Abort will return the screen to the Main Analog Menu.

Assuming that sampling has occurred normally and that the triggering event has been detected, analog sampling will end when all of the post trigger measurements have been collected. The Analog Module will sound an audible "beep" to mark the end of data collection and the measured analog signals will appear on the color graphic display. The display is in graph format with the horizontal axis corresponding to the sampling period (time), and the vertical axis corresponding to the units of measurement of the analog signals. The signal from each channel is displayed as a curve with different colors being used to distinguish different channels.

After sampling has been completed the Analog Data Processing Menu is displayed. This is the primary menu used for the display and analysis of data in the Analog Module. Some of the listed options are used to display analog data measurements in different ways, while other options provide various types of data analysis functions from simple measurement of values and intervals to sophisticated signal processing. Included in these analysis functions are a number of specialized EMG processing applications. A discussion of these display and analysis options will be the subject of the following sub-sections.

14.8.1 Function Keys   The Function keys, whose definitions are shown at the bottom of the menu box of the Data Processing Option Menu, allow additional options that are used in the selection of the current graph.

14.8.1.1 F1 New   Before plotting individual analog channels, one typically creates a new (empty) graph as the current graph. To start a new graph from the Analog Data Processing Menu, the F1-New key is pressed. The existing graph(s) are moved up on the display and space is created for a new graph at the bottom of the display. Any number of curves may now be drawn on this graph using the Channel option.

14.8.1.2 F2 Clear   Alternately, one may wish to clear all the graphs on the display so that the new graph will be drawn using the full display screen. This is accomplished using the F2-Clear key.

14.8.1.3 F3 Erase Last   A third option allows the current graph to be replaced with a new graph, while leaving the previous graphs on the display. This option is selected by pressing the F3-Erase_Last key. The last graph is cleared and the space it occupied may then be used for a new graph. If Erase_Last is selected more than once, the last or lowest previous graph will be erased and the display will be redrawn with all remaining graphs enlarged and one new empty graph area at the bottom of the display.

14.8.1.4 F4 -Export   The F4_Export key selects one additional graph related option. This key is used to produce table prints of numerical curve values from the current graph. When this option is selected you will be asked to indicate a horizontal interval on the current graph. A table will then be printed on the printer with values from each of the data curves on the graph for that interval. Since typical analog sampling contains hundred and perhaps thousands of measurements for each channel, the table print will reduce the number of values printed by selecting data points at measured intervals along the curves.

To complete the table print command a skip factor must be entered for use in printing the data values. Since the Analog Module may measure thousands of values for each channel it is normally not practical to print all values in a table. the skip factor is used to specify the frequency of values to be printed. A factor of 1 would cause every value to be printed. A factor of 2 would cause every other value to be printed. A factor of 10 would cause every tenth value to be printed, and so on. If in doubt, start with a factor of ten and adjust accordingly.

	F1_Channels. The table print normally lists values for all active analog channels. F1_Channels key may be used to print values for fewer channels. Select the first and last channel(s) by pressing the up/down arrow keys and pressing ENTER. Channels must be displayed sequentially. This mode does not allow channels between the first and last channel to be skipped.
	F2_Time. A final option for the table print is to restrict the range of printed values to some time interval that is less than the sampling period. This option is often used when the event being measured is short compared to the entire sampling period.
	F3-SelectGraph. The F3 key is pressed to select the graph for the export information. The current graph will be displayed within a rectangular box.
	Esc-Abort The ESC key is pressed to abort the current menu without saving any changes.
	F10-Done The F10 key is pressed to save the entered information and proceed to the next menu.

After selecting the desired table print options, type the skip factor to be used and press ENTER. The table print will then start on the system printer. Alternately this may be canceled by pressing the F10 Key.

14.8.1.5 F9 Rectify   The F9_Rectify is selected to set or change the rectification mode used on the raw data. The current rectification mode is shown in the upper right corner of the menu box. The choices for rectification are "None" (for no rectification) "Half_Wave" and "Full_Wave". EMG signals are usually integrated using "Full_Wave" rectification.

"Half_Wave" is selected when half wave signal rectification is desired. Half wave rectification causes all negative analog signal values to be graphed as zero values (i.e. the negative portion of each analog signal is removed). This option is frequently used in EMG analysis prior to Envelope or Integration processing, however it may be used with any type of analog signal. When half wave rectification is selected an indicator will show in the upper right corner of the Analog Data Processing Menu.

"Full_Wave" is selected when full wave signal rectification is desired. Full wave rectification causes all negative analog signal values to be graphed as positive values (i.e. the absolute value of each analog signal is graphed). This option is frequently used in EMG analysis prior to Envelope or Integration processing, however it may be used with any type of analog signal. When full wave rectification is selected an indicator will show in the upper right corner of the Analog Data Processing Menu.

14.8.2 1st, 2nd, 3rd   The analog module allows the measurement of up to thirty two simultaneous analog signals. The display of thirty two channels or curves on a single graph would , for all practical purposes, be unreadable. The analog module therefore limits the number of channels or curves on a single graph to nine. To compensate for this limit, more than one graph may be drawn on the display at the same time. The first graph is drawn using the full display screen. If a second graph is added, the first graph is redrawn in the upper half of the display and the second graph is drawn in the lower half of the display. If a third graph is added, each graph is drawn using one third of the display and so on. The lowest or most recently drawn graph is called the current graph. Measurement and analysis functions are always performed using the current graph, with previous graphs displayed for comparison purposes.

In order to simplify the process of determining which channels are to be drawn on which graph, the Analog Module contains a feature called the Plot List. This is simply a list of analog channels (from one to nine) that are to be drawn on a single graph. Three plot lists can be defined in the analog module and they are designated the 1st, 2nd and the 3rd. After each analog sample is collected, or when previously sampled analog data is read from a file, the first plot list is automatically graphed. This is the initial display that appears along with the analog processing menu.

If only a few analog channels are being measured, a single plot list is probably sufficient to display all active channels. In this case, all channels are automatically displayed after each sample. For larger numbers of channels, or if values for different channels are expressed in different units of measurement (the units for each graph are those of the first channel plotted on that graph), two or three plot lists should be used. In this case, more than one graph will be required to display all the analog data.

The Analog Data Processing Menu allows any of the plot lists to be added as an additional graph on the current display through the 1st, 2nd and 3rd options. Each time one of these options is selected a new graph is drawn to display the channels from that plot list. As mentioned, the first plot list is graphed automatically. The second plot list is graphed using the 2nd option, and the third plot list using the 3rd. In this manner, many analog channel curves can be quickly graphed for examination and analysis.

14.8.3 Channel   Plot lists are used to graph groups of channels. In addition, the Analog module allows any single active analog channel to be graphed using the Channel option. When Channel is selected, a list of active channels is presented. Choosing a channel letter will cause the data curve for that channel to be added to the current graph. In this manner, graphs may be created with curves for one or more analog channels in different combinations than the ones defined for the three existing plot lists.

The active analog channels are displayed in the menu box. To select the channel to be added as an additional curve on the current graph simply press the letter key corresponding to that channel.

14.8.4 Expand   The Expand option is selected to expand the current graph so that a horizontal and/or vertical interval of the existing curves is expanded and plotted to the full scale of the graph. This is essentially a zoom function that allows any portion of the current graph to be examined in an enlarged format. When this option is selected the horizontal or vertical interval must be specified either by using the mouse or by typing the endpoint values of the interval. The graph may then be redrawn for this interval, thus performing an expansion of the original graph. Expand may be selected repeatedly, each time specifying an interval on the already expanded graph. In this manner even the smallest detail recorded may be zoomed in.

The usefulness of the expand option becomes apparent when considering that the maximum resolution of the graphic display is 640 points horizontally and 400 points vertically. Analog signals, if recorded to the full input scale, have a resolution of about 4000 units vertically and several thousand units horizontally, depending on the sampling rate and period. To visually observe the smallest detail capable of being measured and recorded, data curves must be expanded. Analysis will not always require this level of detail, and frequently unexpanded curves are sufficient to provide the necessary data measurements.

	X_axis is selected to expand the current graph along the X or horizontal coordinate axis. When selected, the endpoints of the interval to be expanded must be entered. Alternately, the numerical interval may be specified by pressing the F2_Numeric key and typing the lower and upper endpoint values. After the endpoints have been entered the screen will return to the Expand Menu, but the graph will be unchanged. To actually draw an expanded graph the Graph option must be selected.
	Y_axis is selected to expand the current graph along the Y or vertical coordinate axis. This option is identical to the X_axis with the exception of expanding along the vertical axis instead of the horizontal axis.
	Reset is selected to remove all expansion options and return to the original graph. When this item is selected the current graph will be redrawn with the original X and Y axis data ranges.
	Graph is selected to redraw the current graph using the expansion options selected from the Expand Menu. This graph is not automatically expanded each time an option is selected in order to allow both an X and a Y expansion, if desired. Only the current graph will be redrawn. All other graphs remain the same.

14.8.5 Label   The Label option on the Analog Data Processing Menu is used to select from a number of specialized labeling options available in the analog module from the Label Menu.

In addition to providing standard text labels for annotation of analog displays, the labeling options perform various computations on the data values in individual curves and report the results of these computations in label format. In this manner basic analysis and labeling of data curves can occur simultaneously.

14.8.5.1 Normal   Normal labels are text labels entered at the keyboard. Any character string can be added to the display in one of four text sizes and one of a number if colors. Labels may be positioned to any screen location using the mouse. this option is identical to the Label option in the Viewing and Graphing Modules.

After Normal has been selected the screen will ask for the Text Label to be added to the display. The F1_Size key and F2_Color key are used to change the size and color of the labels, this must be done before the label is typed in. Any forty character label may be typed in and ENTER must then be pressed to accept the label. At this point the mouse is used to position the label to the desired location of the screen.

NOTE

If the color or size of the label is to be changed, it must be done before the label is typed.

	The text of these labels is automatically created by the analog module as a result of a data measurement of computation,
	These labels are connected to specific screen locations with lines to indicate the point or points to which these measurements apply.

There are several options that may be performed when analog samples are saved to allow identification of the sample and to limit the amount of data that is actually saved.

	F1-Channels specifies fewer than the full number of active channels to be saved if not all of the measured data is needed. When F1-Channels is pressed the first and last data channels can be selected.
	F2-Time selects a portion of the sampling period if data from the entire period is not needed. Once the F2-Time key is pressed the mouse is used to select the portion of the curves to be saved.
	F3-SelectGraph is used to select or change the currently active graph. When this option is selected a new graph can be selected using the mouse or the up/down arrow keys. The current active graph is displayed within a rectangular box.
	ESC-Abort is selected to abort the current menu without saving any changes.
	F10-Done is selected to advance to the next menu.

14.8.7 Analysis (Analysis Options and EMG Signal Processing)   The Analysis option on the Analog Processing Menu is used to select a number of special options from the Analysis Options Menu. These options may be used for any analog data, but have been especially designed to support the analysis of EMG signals. One exception is the Force-Vectors option which has been designed to support force platform data analysis.

EMG signals are made up of numbers of individual pulses or spikes resulting from the firing of individual muscle motor units. Different motor units fire at different rates resulting in a composite EMG signal that is the sum of individual signals at varying frequencies. Classical numerical methods, such as Fourier analysis, can be applied to the composite signal to estimate the component frequencies.

When either the Power, Envelope, Spike or Integral option is selected, a menu box containing a list of the active channels, displayed on the most recent graph of measured analog values may be selected for power spectrum analysis. Select the desired channel by highlighting the channel name and pressing ENTER or selecting corresponding channel letter.

NOTE

It is important to realize that while the Power, Envelope, Spike and Integral options have been presented as to apply to EMG data signals, they may be applied to any type of analog measurement. The Power, Envelope, and Integral options could just as well be used for force platform data or other types of laboratory signals. Spike analysis is more directly related to EMG signals, although additional areas of application are possible.

14.8.7.3 Spike   EMG signals consist of rapid pulses or waveforms representing a series of individual motor unit action potentials commonly referred to as spikes. The Spike option on the analysis menu is used to perform a spike analysis on an interval of an EMG curve. Spikes tend to appear in groups called motor unit action potential trains and this option allows a separate spike analysis to be performed on each train. A spike analysis reports the following information:

	the number of spikes in a train,
	the amplitude and duration of each spike,
	the average amplitude and duration of all spikes,
	the average spike frequency (inverse of the spike duration).

After a channel has been chosen, the current spike analysis threshold value is shown in the menu box. This is typically an EMG pulse train or interval of significant motor activity. A new value may be entered to change the threshold. Spike analysis will proceed once the threshold value has been entered.

The threshold value is the minimum amplitude required for a signal variation to be measured as a "spike". A spike is defined as a variation in the raw EMG signal starting at a negative minimum, proceeding through a positive maximum, and ending at the next negative minimum. The spike amplitude is defined as the difference between the average of the two negative minimum values and the positive maximum value. The threshold value is the minimum spike amplitude. Variations below this amplitude are not considered as spikes.

Spike analysis is commonly performed on raw unrectified EMG signals, although this may be applied to any type of bipolar, varying from positive to negative, signal. A typical threshold value for EMG signals is 100 microvolts of motor unit action potential as measured with surface electrodes.

The monochrome monitor displays the results of the spike analysis after it has been performed. The menu box contains four columns of individual spike measurements (amplitude and duration of each spike found in the specified interval). If there are more spikes than fit in the menu box the F1-NextPage and F2_LastPage keys may be used to scroll through the list. Alternately, the F3-HardCopy key may be used to print a table of all spike values. The F10-Done key will return the screen to the Main Analog Menu.

14.8.7.4 Integral   In EMG analysis, total myoelectric activity is measured as the integral of (area under) the EMG curve. This is frequently referred to as integrated EMG. The Integral option on the analysis menu is used to perform integration on any selected portion of an EMG curve. The Integral analysis option differs from the Integral labeling option in that the integral is displayed as an additional graph rather than as a label. This presentation method allows different integral formats to be used.

The first integral format graphs the total EMG integral as a function of time. This is a curve of increasing value, with the slope of the curve indicating the rate of EMG activity at that point in time. The second format graphs the increasing EMG integral to a preselected limit value, then resets the integral curve to zero and continues graphing the EMG integral. This produces a series of peaks of the same amplitude, with the frequency of the peaks indicating the rate of EMG activity. The third format graphs increasing EMG integral values for a specified period of time, then resets the integral curve to zero and continues graphing the EMG integral. This produces a series of peaks with a constant frequency, while the amplitude of the peaks indicates the rate of EMG activity.

After a channel has been selected for integral processing, the reset mode must be selected.

	Value is selected to integrate the selected channel with a reset on a fixed value. The integral curve will increase until this value is reached, then the curve will be reset to zero and integration will continue. This creates an integral curve with a series of peaks of constant magnitude. The frequency of these peaks indicates the overall rate of increase of the integral. The smaller the reset level, the more frequently the integral curve will reset to zero. Too small a value will produce a curve of densely packed spikes that is difficult to interpret. To large a value will produce a curve similar to a No-Reset integral.
	Time is selected to integrate the selected channel with a reset on a fixed time interval. The integral curve will increase over this interval, then the curve will be reset to zero and integration will continue. This creates an integral curve with a series of peaks of constant frequency. The magnitude of these peaks indicates the overall rate of increase of the integral. As with value, the smaller the reset level, the more frequently the integral curve will reset to zero. Too small a value will produce a curve of densely packed spikes that is difficult to interpret. To large a value will produce a curve similar to a No-Reset integral. Some experimentation may be necessary to arrive at the best reset value for the data.
	No-Reset is selected to integrate the selected channel over the entire sampling period without a reset. The integral curve will be a continually increasing curve with the magnitude of the curve indicating the total integral value to that point.
	Units is selected to change the time units for reporting integrals. the current time units are shown in the upper left corner of the menu box. The choices for time units are milliseconds and seconds. Thus, for example, if EMG signals were being measured in millivolts, the integral values could be reported in millivolt-seconds or in millivolt-milliseconds.
	Rectify is selected to change or set the rectification mode used in computing integrals. The current rectification mode is shown in the upper right corner of the menu box. EMG signals are usually integrated using Full_wave rectification. The full rectification process is reviewed in subchapter 14.8.1.5.

14.8.7.5 Force Vectors   The Force_Vectors Option Menu is used in conjunction with force platform data measurement, as when a force platform is used for gait analysis. This option allows the forces applied to the platform to be graphed as a series of force vectors originating at the applied force. To use this option, the Plate option on the analog options menu must first be selected to define the force platform input channels. In addition, the actual input signals measured must correspond to the listed input signals provided by the Plate option.

The F1_Export key selects the export option. This key is used to produce table prints of numerical curve values from the current graph. When this option is selected a horizontal interval must be selected. A table will then be printed on the printer with values from each of the data curves on the graph for that interval. Since typical analog sampling contains hundreds and perhaps thousands of measurements for each channel, the table print will reduce the number of values printed by selecting data points at measured intervals along the curves.

The F2_Clear key clears the entire display and starts a new graph as the only graph on the display. Additional curves will be drawn on this graph using the entire display.

The F3_Erase_Last key erases the current graph and expands the other graph(s) on the display to fill the space occupied by the current graph. The previous graph then becomes the current graph. If there is only one graph on the display the F3 key is identical to the F2_Clear key.

When Force_Vectors is selected, an additional menu is presented to allow selection of the viewing plane for the graph of force vectors.

	X_vs_Z is selected to graph force vectors in the X-Z plane, as viewed along the Y axis. the graph shows the force platform in the X-Z plane and force vectors drawn from the surface of the platform at the point of application of the force. the length and direction of each vector corresponds to the magnitude and direction of the applied force at that point in time. force vectors are drawn at equal time interval spanning the entire sampling period.
	Y_vs_Z is selected to graph force vectors in the Y-Z plane, as viewed along the X axis. this is identical to the X_vs_Z graph but at a different angle.
	Both is selected to graph the X-Z and the Y-Z planes, as viewed along the Y and X axes.
	3D is selected to graph force platform vectors in 3-Dimensions. the graph shows the force platform in 3-D and force vectors from the surface of the platform at the point of application of the force. the length and direction of each vector corresponds to the magnitude and direction of the applied force at that point in time. X selects the displayed image to be rotated about the X coordinate axis by the angle quantity displayed in the upper right corner of the menu box. the direction of rotation is determined using the "right-hand" rule. the display coordinate axes are indicated by the arrows on the color monitor. Y selects rotation about the Y axis. Z selects the Z axis rotation. Reverse changes the direction of subsequent rotations by changing the sign of the angle quantity shown in the upper right corner of the menu box. this option allows reversing rotations in a more convenient manner than selecting the Angle option and entering the same angle with the opposite sign. The direction of rotation is determined by the "right-hand" rule. This rule states that positive rotations are performed in a counter-clockwise direction and that negative rotations are performed in a clockwise direction as viewed along the axis of rotation. Angle is selected to specify a new rotation angle. the rotation angle is the amount that the image is rotated about the selected axis each time a rotation is performed. this value is displayed in the upper right corner of the rotation menu box. When this item is selected a new value is entered and the screen returns to the Rotation menu. F1-XvsZ is selected to graph force platform vectors in the XZ plane (as viewed along the Y axis). F2-YvsZ is selected to graph vectors in the YZ plane (as viewed along the X axis) F3-ReStart is selected to return to the original 3-D image.
	COP is selected to graph force platform vectors in the X-Y plane, as viewed along the Z-axis of the force platform. The graph shows the force platform in the X-Y plane and the point of force application on the surface of the platform.
	Moments is selected to graph force platform moments about the axes of the platform. X-Moment is selected to graph the moment about the x-axis of the force platform. This is usually the short axis of the force platform. Y-Moment is selected to graph the moment about the y-axis of the force platform. this is usually the long axis of the force platform. Z-Moment is selected to graph the moment about the vertical axis of the force platform. Free-Z is selected to graph the moment about the vertical axis.
	Ax/Ay is used to graph the location of the point of force application on the platform in Cartesian coordinates. Ax is the x-component of the point of force and Ay is the y-component.
	Options is selected to change the display parameters for the force platform. When this option is selected and additional menu (Figure 14-16) will appear to specify the parameters. Plates selects the number of plates for vector display. one is used for one plate, but if two plates are used, force vectors may be displayed in one of two ways: Two is selected to display vectors from the two plates independently and Both will plot vectors not only while on the two plates but also between the two plates, thus simulating one large plate. Mode selects the plate vector mode. COP displays vectors from the calculated Center-Of-Pressure on the plates. Point displays vectors from a single point (the center of the plate). time displays the force vectors as a function of time. #Vectors is used to change the number of vectors displayed on the force-vectors graph. the new number is simply typed in and ENTER pressed. To keep the current number ENTER is pressed. The more vectors the denser will be the vector display and the more difficult it will be to distinguish individual vectors. the maximum number of force vectors is 100. Time(sec) is the time (in seconds) between color change of force vectors in both COP and Point mode. Delay selects the time between the force vector display on the color monitor. For no delay a value of 0 is entered. the larger the number the longer the delay. the maximum number for delay is 99. Threshold% selects z-force threshold as a percentage of the maximum force displayed. for example: if the maximum z-force is 100 pounds and a threshold of 50 is entered then only the vectors with a magnitude of 50 or greater will be displayed. F-10 will return the screen to the Select Force Vector Option Menu.

The number of vectors drawn on each graph is displayed in the upper right corner of the menu box. By default 50 vectors are drawn, distributed evenly in time over the sample. The #Vectors option may be used to change the number of vectors before the graph(s) are drawn. Some experimentation may be necessary to determine the optimum number of vectors for a given application.

14.8.7.7 Jump   Jump is selected to perform a vertical jump analysis using analog force plate data. for optimal results using this option several steps should be taken during data collection. First, the trigger level should be set to a negative value. this will allow data collection to be triggered from the keyboard. the plate should be zeroed when there is no weight on the plate. the subject should then step on the plate and remain motionless as the operator triggers the data collection with the keyboard. After approximately 1 to 2 seconds, the subject should jump and land back on the plate and remain still for approximately 5 seconds.

The color graphics display shows the Vertical Jump Report Table below the graphed force platform data. eight points (labeled A through H) are labeled on the z direction force graph and are used for the row labels in the table. Column labels include Time, Force, Force-Weight, %Weight, Time change between points, Force change between points and Slope (impulse). Weight and max height are also listed below the table. the display on the color monitor can be sent to the printer by pressing the Ctrl and Print Scrn keys simultaneously.

14.8.8 Options   The Options item on the Analog Processing Menu is identical to the display option from the Main Analysis Menu.

14.9 ADVANCING TO THE NEXT ANALOG SAMPLE   The display and analysis options on the Analog Data Processing Menu (Figure 14-8) have now been discussed. On final step remains to complete the normal flow of analog processing; advancing to the next analog sample. When the processing of the current sample is complete, Quit is selected on the analog Processing Menu. Before returning to the main menu to allow additional sampling, the program displays a new menu.

The first two options, Clear and Save, control the status of the graphic display following the next analog input, while the third option, Abort is used to cancel this quit command and return to the processing of the current analog sample. this latter option is provided to prevent inadvertent data loss since the current sample is discarded when the program returns to the Main Analog Menu (Figure 14-1).

Clear is selected when the graphic display is to be cleared prior to graphing the next analog sample. this is the normal mode of display and results in each sample being graphed separately. Save is selected when the current display is to be retained and the next analog sample is to be graphed as a new graph on the same display. this option allows consecutive analog samples to be compared graphically.

NOTE

The actual data values for the previous graphs will not be present once an additional analog sample has been collected, so the comparison is limited to the graphs already on the display.

The individual input signals must mow be defined in the analog module. Select Options on the Main Analog Menu then select Channels on the Options Menu. A table of the possible analog channels will appear on the display. This is called the channel Definition Table. For each channel, this table contains:

	channel designator (A through P for 16 channels, A through p for 32 channels),
	channel description (up to 10 characters),
	units of measurement (for reporting purposes),
	conversion factor in units/volt,
	an offset value, in volts, corresponding to the zero value in the selected units of measure for that channel.

Below this table is a menu that is used to enter or change the table entries on the individual channel basis.

Entry of an accurate conversion factor and offset for each channel is critical if measurements are to be reported correctly. for example, if force platform input is being measured, and it is desired to report results in pounds, the output of each force platform channel in pound/volts must be known and entered in the channel table. If the conversion factor is not known, use volts for Units and enter 1 for Units/V. Most laboratory measuring devices can be adjusted for a zero offset (i.e. zero volts of output signal equals zero measurement units). If analog signals do not have a zero volt offset, measure the actual offset corresponding to zero measurement units (this can be done using an analog channel with 1 unit/volt and a zero offset), and enter this value in the Channel Table. The measured signal will then be adjusted by this offset prior to being graphed or analyzed.

Whenever a new data file is created in the analog module, the contents of the channel definition table, as well as the analog input parameters, are saved in that file. If there are several standard input configurations that will be used for sampling (e.g. force platform, EMG equipment, etc.) each channel and parameter configuration can be saved in a separate file. In this manner, one only needs to access an existing file in order to configure the analog module for a given type of data collection. In addition, the current configuration is saved on exit from the analog module and is restored when the module is run again.

This completes the discussion of analog channel setup. In practice, one typically connects the input signals and then performs a series of trial measurements to establish signal levels, sampling times, and adjustment of signal sources to achieve proper calibration. A discussion of specific laboratory and clinical data measurement techniques is, however, beyond the scope of this manual.