ARIEL ANALOG PROGRAM
INTRODUCTION
The ARIEL ANALOG
software is used as a general purpose laboratory data measurement and analysis
sub-system. The module is designed to
sample, save and present analog signals from many independent channels. A fast measurement rate is possible, with
high resolution and programmable input voltage ranges. Data signals are measured to a 12 bit (1 in
4096) resolution. A number of
triggering options are provided to assist in the capture of transient data and
to allow the synchronization of the analog module with external events. The analog module also includes a set of
specialized electromyogram (EMG) signal processing options. EMG data samples can be analyzed using a
number of sophisticated techniques including spike analysis, signal
rectification and integration, envelope processing and spectral analysis.
WHAT’S NEW IN ANALOG 1.0
A few of the new features
you will see in ANALOG version 1.0
1.
High Sampling Rates. Data can be sampled at rates
up to 330 kHz.
2.
APAS Tool Bar. A toolbar has been added to
allow the user to activate individual APAS modules from within the main
programs.
3.
Real-Time COP. Software support for real time
center-of-pressure using a force platform has been added.
4.
Vectors Display. The Ariel Vectors program has
been integrated into the program.
SYSTEM REQUIREMENTS
The following table
provides the basic guidelines for minimum and recommended hardware to provide
the best possible performance. The
software requires a minimum of Microsoft Windows 95/98 and APAS-2000 Revision
2.1 or later.
Component Minimum Recommended
_____________________________________________________________________________________________________________________________________________________
Pentium
Computer Pentium 233 Pentium
II 333 MHz or higher
RAM
32 MB 64
MB or more
Analog
Board CES#3 (Retrieve
Only) Industry
Standard A/D
TO START THE ANALOG PROGRAM
1. Double-click the ANALOG icon located in the APAS System
window group. The main ANALOG window
will appear.
SCREEN LAYOUT
Prior to performing the ANALOG
module, you should take the time to familiarize yourself with the format and
contents of the various screens listed below:
THE APAS TOOL BAR
You can activate any of
the APAS software modules from within the current program by selecting the
icons located on the APAS tool bar. The
tool bar is toggled on/off using the APAS Toolbar command in the VIEW menu. A check mark in the left column of the menu
indicates that the toolbar is currently active. The toolbar can be re-located anywhere in the main program window
by dragging it with the mouse. The
following program modules can be activated by clicking the appropriate
icon. Icons are pictorial
representations of programs, commands or functions.
THE TOOL BAR
You can activate many
functions by selecting the icons located on the ANALOG program tool
bar. The tool bar is located near the
top of the window. The icons in the
Analog Tool Bar can be divided into three sections. Icons are pictorial representations of commands or functions. You can access the following commands by
clicking the appropriate icon.
MAIN
ANALOG TOOL BAR
The Main Tool Bar icons can be used to activate general file
commands.
SAMPLE/RETRIEVE
TOOL BAR
The icons in the Sample/Retrieve tool bar will change
depending on the current file MODE. The
Tool Bar for the A/D mode is shown on the left while the Tool Bar for the FILE
mode is displayed on the right.
GRAPHING
TOOL BAR
Sampled data can be displayed using the icons in the Graphing
Tool Bar.
THE STATUS BAR
The status bar provides
useful information about the current status of the file during the Analog
process. The status bar is located at
the bottom of the Analog window. The far-right
side of the status bar is divided into three separate fields. The left field
indicates the make (if any) of the force platform. The ANALOG MODE field indicates the current mode. The A/D mode is used for data sampling while
the FILE mode is used for retrieving previously saved data. The third field is the TRIAL INDICATOR. The first number indicates the current data
trial within the analog file while the second number indicates the total number
of saved data trials.
THE PARAMETERS BAR
You can specify most
analog functions by selecting the desired option located on the ANALOG
Parameter bar.
Last Channel - 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 is set by
specifying the last active channel. The
active analog channels appear in the channel table in the main Analog window. 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.
Trigger Channel - The Trigger Channel is used to select the channel
used for triggering. It may be any of
the active analog channels shown in the Channel Table. The current trigger channel is displayed in
the Analog Parameters Bar.
Period - The 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 as the 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.
Rate/Channel - The Rate/Chan is used to set the sampling rate for
analog data collection. All active
channels are sampled at the specified rate.
Trigger Level - The Level is used to set 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 sample values is to
start.
Pre-Trigger % - The 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 waved with new samples replacing the oldest ones. This parameter can be set to any value between) (no pretrigger)
and 99. It is possible that less 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.
CREATING A NEW ANALOG FILE
Unless analog measurements
are to be immediately processed and then discarded, they must be saved in data
files on the computer. Data files can
be created using the following procedure.
1. Choose the NEW command from the FILE menu. The OPEN File Dialog box will appear.
The OPEN File Dialog box looks
for a particular type of file (files that have the extension of (*.ANA). The OPEN File Dialog box can be used to
specify the Drive, Directory, and Name of the sequence file to be created.
2.
Analog input is
controlled by the analog sampling parameters that are displayed in the
Parameter Bar. These parameters must be
set before the Analog Module may process the analog measurements. Please refer to the Parameter Bar section
for additional information. Specify the
following parameters to match the data collection requirements:
Last Channel (LastCh)
Trigger Channel (TrigCh)
Period
Sample Rate (Rate/Ch)
Trigger Level (TrigLev)
Pre-Trigger Percent (PreTrig%)
3.
Select the CHANNELS
command from the OPTIONS menu to specify the Channel Information for the
active analog channels. The Channels
command is used to set or change the individual analog channel definitions in
the analog channel table.
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.
4.
Select the PLATES
command from the OPTIONS menu to activate/de-activate the force plate
software. The Plate command is used to
define special force platform (force plate) processing by assigning a block of
analog input channels to predefine 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 command 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.
5.
Set the desired
channels on Plot Lists 1 through 3 by clicking in the desired column.
6.
You are now ready to
sample the analog data
CREATING AN EMG FILE (EXAMPLE)
This example illustrates
the procedure for creating a two-channel EMG file using electrodes with a gain
of 1000.
1. Select FILE, NEW to create a new *.ANA file.
2. Use the Parameter Bar to set the following parameters:
Last Channel (LastCh): B1
(Two channels will be sampled)
Trigger Channel (TrigCh): A1
Period: 5 seconds
Sample Rate (Rate/Ch): 1000 samples/sec/chan
Trigger Level (TrigLev): 0.2 mv
Pre-Trigger Percent (PreTrig%): 10%
3. Select OPTIONS, CHANNELS to specify the Channel
Information for the active analog channels.
Channel A:
Description: Channel
1
Units: mv
Units/volt: 1 (Since gain=1000 and
1000mv=1volt) Offset: 0 Calculated during the ZERO process
Channel B:
Description: Channel
2
Units: mv
Units/volt: 1
Offset: 0
4. Select OPTIONS, PLATES and select NONE to
de-activate the force plate software.
5. Set the desired channels on Plot Lists 1 through 3 by
clicking in the desired column.
Click in the 1st column for Channel A1 and 2nd column for
Channel B1.
6. You are now ready to sample the analog data.
CREATING A FORCE PLATFORM FILE (EXAMPLE)
This example illustrates
the procedure for creating an analog file for a single AMTI force platform
(Gain = 2000 and Excitation voltage = 5)
1. Select FILE, NEW to create a new *.ANA file.
2. Use the Parameter Bar to set the following parameters:
Last Channel (LastCh): F1
(6 channels total)
Trigger Channel (TrigCh): C1
(Vertical force channel)
Period: 5
seconds
Sample Rate (Rate/Ch): 1000
samples/second/channel
Trigger Level (TrigLev): 10
lbs
Pre-Trigger Percent (PreTrig%): 10%
3. Select OPTIONS, CHANNELS to specify the Channel
Information for the active analog channels.
4. Select OPTIONS, PLATES, AMTI to activate the
software drivers for the AMTI force platform.
Select the INFO tab and enter the following:
Length Units: Inches
Force Units: Lbs
#Plates: One
1st Plate Channel: A1
Select the PLATE#1 tab and enter the following:
Transducer Depth: 1.36
Length: 20.00
Width: 18.25
Select the CAL#1 tab and enter the following:
Force Plate Constants: FX = 2.883 uV/Vo/Lb
FY
= 2.864
FZ
= 0.725
Moment Calibration Constants: MX = 1.770 uV/Vo/ft-lb
MY
= 1.770
MZ
= 3.423
Select the ELECTRONICS tab and enter the following:
Excitation: 5.00
Volts Gain: 2000
5. Select OK to Calculate Plate Conversion Factors. This will automatically update the
Units/Volt entry in the Channel Information Table.
6. Set the desired channels on Plot Lists 1 through 3 by
clicking in the desired column.
Click in the 1st column for Channel C1 (Z direction force)
Click in the 2nd column for Channels A1 and B1 (X and Y
direction Forces)
Click in the 3rd column for Channels D1, E1 and F1 (X, Y, Z
Moments)
7. You are now ready to sample the analog data.
ANALOG MEASUREMENT PROCESS
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.
1. Choose the START command from the SAMPLE
menu (or select the GO icon from the tool bar) to initiate Analog
sampling. When Start is selected, the
analog module displays a reminder message to prepare for analog
measurement.
At this point actual sampling
has not begun and three options are available.
The first option is to begin analog sampling by selecting the OK
button. The second option is to abort
by selecting the Cancel button to return to the main Analog window. 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. The third option is to zero
any voltage offsets on the active analog channels.
2. Select the ZERO button to compute the
offsets for the active analog channels.
3. Select the OK button to begin the
sampling process. 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 in progress.
Sampling may be aborted at
this time by selecting the Cancel button. The Cancel 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.
Selecting Cancel will return the screen to the main Analog window.
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 active
analog signals in Plot List #1 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 graphed data is displayed in the Analog window. 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.
4. Select FILE, EXIT to exit the ANALOG program.
OPTIONS
The ARIEL ANALOG
software contains many options designed to enhance the analog process. Selecting the OPTIONS menu accesses these
options. Available options allow for
selecting the setting system parameters, specifying channel information and
specifying force platform parameters.
SYSTEM OPTIONS
The System command
is selected from the OPTIONS menu when the default program mode or
autoload option are to be changed. When
this command is selected, the System Options menu will be displayed indicating
the current program mode and autoload option when opening an analog file.
PROGRAM MODE
The System Options menu is
used to set the default program mode when opening a file. The A/D mode is used for measuring and
saving analog data values. It is called
A/D mode because actual analog-to-digital conversion is performed.
In the File mode, analog
sampling cannot be performed using the analog-to-digital interface. This option allows previously sampled and
saved data to be read or retrieved from a data file. In the File mode, one may advance to the next saved sample in the
file or backup to the previous saved sample.
When a sample is read, the information is displayed in the same manner
as when analog sampling has been performed.
It is possible to change
between A/D mode and File mode at any time using the icons in the Analog
Sample/Retrieve Tool Bar. (NOTE: Changing the mode using the Tool Bar does
not affect the default setting.) For
example, if data is being sampled and saved in a file, 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.
AUTOLOAD 1ST SAVE
The System Options menu
can also be used to set the auto-load option.
When this option is activated (YES), the channels listed in Plot List #1
of the first trial in the analog file will automatically be graphed. If this option is inactive (NO), no data
will be plotted.
CHANNELS
The Channels command is
used to set or change the individual analog channel definitions in the analog
channel table. When this option is
selected, the Misc. Options menu 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 section on Analog Sampling And Channel
Definition, to allow the specific features of the analog module to be presented
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.
PLATES
The Plate command is used
to define special force platform (force plate) processing by assigning a block
of analog input channels to predefined force platform signals. When this option is selected, the Plate
Information menu is displayed. 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 specified. 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 Plate Information menu will be displayed.
The information required by the software depends upon the make of force
platform selected. The AMTI plate has
been used for this discussion. Select
each of the following tabs to enter the required information.
The Info tab is
selected to specify the desired units for length and force, the number of
plates being used and the first platform channel. The units selected for length and force will be used for
reporting data results and can be changed at any time. Outputs from the force platform must be
connected sequentially therefore, only the first channel must be
specified. 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 computed force plate quantities are available for
graphing and analysis.
The Plate #1 tab is
selected to enter dimensions for the first force platform. The Transducer Depth is obtained from the
force platform calibration information and is equal to the vertical distance
from the top of the force platform to the top of the transducer. The Length and Width are also obtained from
the force platform manual. All
Dimension values must be entered in the user specified units.
The Plate #2 tab is
selected to enter dimensions for the second force platform as well as the
orientation of the first force platform to the second force platform.
Refer to the following
diagram for the orientation of two force platforms.
Required information for
two force platforms includes:
Translation from Origin on both the X and Y directions
Rotation Angle - Measured Counter-Clockwise, this number represents
the angle from force platform #1 to platform #2.
The CAL #1 and #2
tabs are selected to enter the Force and Moment Calibration Constants. These values are obtained from the
calibration values supplied in the force platform documentation.
Electronics is selected to enter the force plate amplifier
information. The required information
is dependent upon the type of force plate being used. This information can be obtained by reading the current settings
on the force plate amplifier hardware.
REAL TIME CENTER-OF-PRESSURE (COP)
The Real Time
Center-of-Pressure (COP) mode provides a method to measure and analyze balance
and stability parameters. This type of
analysis can be used for testing the effects of orthotics and prosthetics,
evaluating sports performance requiring stability, and examining orthopedic or
neurologic dysfunction. Suggested steps
for using the COP option are listed below.
1.
Configure force plate
setup as described in the section titled Creating A Force Platform File.
2. Select the COP command from the SAMPLE menu (or the COP icon in th