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Whisper User Manual - Motion Lab Systems, Inc.

1. I I I L l 387 50 TE be eee a ee loners faeces Caan Vee oe ee ee I I I I I I I t I I I E I I ULI _ o T OoOo OoOo OoOo Oooo MINI iy Jal LI I I LI i ai a a i o li Le T LI i SCR i ii ee eee ee eee ee enel eee eee eee L 5416 5579 5741 5904 6066 6229 6392 6554 67417 6879 7042 Sample Figure 28 MLSviewer can display the raw data in an easy to understand view This allows the user to check any DST file to verify that the format is correct and that the DST file header contains accurate information about the data A typical Mode 0 or Mode file should contain EMG data in the range of 800 to 800 uV and be preceded by five positive going timing pulses The MLSviewer has a flexible viewing mode that can be used to display the entire data recording as well as allowing the user to zoom in to view individual data samples in an easy to use graphical display The MLSviewer data display is auto scaled and allows the user to rapidly determine that the Whisper data has been scaled correctly Figure 28 illustrates the transition Whisper User Manual from the initial Whisper timing pulses to the start of the simulated EMG signal The data in this illustration a DST file is shown scaled in the range of 756 to 718 vertical scale over a sample range of 5416 to 7042 Most of the initial problems with generating DST files from raw Dataq or C3D
2. Wir ra O pre Pra camino battersi Figure 8 A typical EMG test setup It s a good idea at this point to connect the Whisper to your EMG recording system in order to test that the Whisper installation has been successful EMG systems and recording configuration vary considerably so these instructions are quite general You may need to read the instruction manual for your EMG system and recording system in order to complete this test Prepare your EMG recording instrumentation to record a signal during at least 22 seconds Choose the gain of your EMG instrumentation channel such that your EMG instrumentation will not saturate when the standard Whisper test signal is applied Your EMG instrumentation should expect to see a maximum EMG test signal amplitude of 1 mV If your EMG system has high and low pass filters then they should be set to allow the maximum bandwidth signal to pass with minimum attenuation Set both the DIF MODE Differential Mode Signal and COM MODE Common Mode Signal switches in the on position if you have bi polar EMG instrumentation If your EMG instrumentation is mono polar then set the COM MODE switch off Now the Whisper is ready for use you can switch on the Whisper using the POWER switch on the right side of the front panel The LED above the switch should light up green At this point the Whisper is ready to generate a signal at surface EMG levels when you press the start button The Whisper will st
3. Connectthe Whisper to your EMG instrumentation as described earlier 2 Select the test mode Set the differential mode and common mode switches in the appropriate positions 3 Prepare your recording instrumentation such that it can record the standard test signal without saturating for at least twenty two seconds 4 Switch the Whisper on 5 Push the Start button and commence recording the EMG signal release the Start button within one second and check that the LED turns orange red 6 Wait until the LED turns green again 7 Store the recorded data for future analysis 8 Switch the Whisper off This protocol can be used in every test mode In order to be able to extract test parameter values from a recording it is necessary to verify whether the recording has been made in an appropriate way For the following test modes the recording should therefore satisfy the following criteria Mode 0 mode 1 e Be sure that you have recorded each of the five leading pulses e Be sure that you have recorded fifteen seconds of digitized EMG Mode 2 e Be sure that you can see a sine wave in the recording after six or seven seconds If your recording satisfies the particular criteria it is possible to determine the values of the test parameters If your recording does not satisfy the particular criteria you need to execute another recording following the protocol described above Interpreting the Test Results The results of the Whi
4. in microvolts These parameters are calculated from the Noise Offset file Since in a Noise Offset test does not produce any differential or common mode signal during the test the Noise and Offset parameters can be calculated over the complete file The RMS noise is determined by the RMS value of the recording while the Offset is equal to the Mean value of the recorded signal The Results File As soon as the Spot Record Analyzer has finish an analysis it stores the results of the analysis in a results file This file will be written in ASCII text format The name of this file will automatically be generated and has the format YYnnnn RES where YY Year and nnnn is a number that is incremented each time a results file is created The results file will be written to the same directory as the data The Spot Record Analysis is complete as soon as the application has completed writing the results file to disk Once the Spot Record Analysis is completed the Exit button will appear in the message controller window If you click on this button you will return to the Spot Record Analysis screen Printing a Spot Record Report Generator The Report Generator option from the Spot Record Analysis menu works in exactly the same way as the Spot Record Analyzer option The only difference is that the Report Generator will print the results to a printer at the end of each analysis You can select the Report Generator option from the Selection window
5. the Netherlands a full Equipment Test has been done with a Whisper using a Klab SPA20 pre amplifier a KL100 raw EMG amplifier and a TRI 815 AD board The results of this test are provided in the data directory of the software YOURSIM RES and are also shown in Appendix Al File Descriptions e 61 62 e File Descriptions Whisper User Manual Appendix A1 EMG Equipment Tester Output This appendix shows the outcome of a full equipment test of a Whisper EMG signal generator at the R R D laboratory in Enschede the Netherlands The results of this test can also be found in the file YOURSIM RES at the data diskette which is provided with the Whisper package DST 1 0 EXP 1 0 09 28 95 Enschede SEXPeriment CAMARC II Specimen Test Result file 09 28 95 Ampl Freq DynTest file 950928E2 DST C N ommon Mode Test file 950928C2 DST oise Offset Test file 950928N2 DST Results 4 11111 2 000167E 2 2 011645E 2 1 983335E 2 2 014467E 2 6 542840E 1 5 730922E 1 3 880684E 1 4 920955E 5 794341E 1 5 744390E 1 5 794341E 1 5 744390E 1 2 247805E 1 2 247805E 1 2 247805E 1 2 247805E 1 3 096976E 1 3 096976E 1 3 096976E 1 3 096976E 1 7 043122E 1 6 993171E 1 7 043122E 1 6 993171E 1 1 024750E 3 1 024750E 3 1 024750E 3 1 024750E 3 3 300000E 1 3 300000E 1 3 300000E 1 3 300000E 1 2 000000E 0 1 000000E 0 0 000000E 0 1 000000E 0 2 000000E 0 1 000000E 0 1 000000E 0 2 000000E 0 2 000000E 0 1 000000E 0 1 000000E
6. 0 1 000000E 0 2 000000E 0 0 000000E 0 0 000000E 0 1 000000E 0 3 000000E 0 2 000000E 0 0 000000E 0 0 000000E 0 3 000000E 0 0 000000E 0 0 000000E 0 1 000000E 0 2 000000E 0 4 000000E 0 0 000000E 0 0 000000E 0 0 000000E 0 2 000000E 0 2 000000E 0 1 000000E 0 0 000000E 0 2 000000E 0 0 000000E 0 2 000000E 0 1 000000E 0 3 000000E 0 1 000000E 0 2 000000E 0 4 900000E 2 4 920000E 2 4 890000E 2 4 940000E 2 5 500000E 1 5 700000E 1 5 900000E 1 6 100000E 1 6 200000E 1 6 200000E 1 6 100000E 1 6 000000E 1 5 500000E 1 5 600000E 1 5 400000E 1 5 900000E 1 5 200000E 1 5 200000E 1 5 200000E 1 5 300000E 1 4 900000E 1 4 800000E 1 4 800000E 1 4 700000E 1 4 400000E 1 4 600000E 1 4 500000E 1 4 300000E 1 Whisper User Manual Appendix A1 e 63 4 500000E 1 4 400000E 1 4 100000E 1 4 000000E 1 3 800000E 1 3 800000E 1 3 900000E 1 4 000000E 1 3 500000E 1 3 400000E 1 3 400000E 1 3 400000E 1 3 200000E 1 3 300000E 1 3 200000E 1 2 800000E 1 2 900000E 1 2 900000E 1 3 000000E 1 2 900000E 1 2 500000E 1 2 700000E 1 2 700000E 1 2 500000E 1 2 400000E 1 2 100000E 1 2 300000E 1 2 600000E 1 1 900000E 1 2 100000E 1 2 100000E 1 2 100000E 1 1 600000E 1 1 800000E 1 1 800000E 1 1 600000E 1 1 600000E 1 1 700000E 1 2 000000E 1 2 000000E 1 1 500000E 1 1 600000E 1 1 300000E 1 1 400000E 1 1 200000E 1 1 300000E 1 1 400000E 1 1
7. 1 000000 individual channel SCALE values must be set to 0 0048828 or 0 0024414 to obtain analog data scaled in Volts when sampled by a 12 bit ADC that is measuring a 10V or 5V input range respectively Many commercial motion capture systems use a standard naming procedure for data recording trials that may not allow you to specify the standard names used by the EMG Testing software If you are using one of these systems then it may be necessary to copy and rename the C3D files after recording to facilitate the use of the Whisper EMG test software Variable Gain Systems As described earlier the calibration procedure is for an MA 100 system is simple A calibration recording is made using the internal calibration source to apply a known calibration source to each EMG input Since we know the input signal level 200uV RMS sine wave all we need to do is directly measure the recorded level of the resulting output signal to calculate a scaling factor to record data scaled in uV The exact method of generating a C3D file will vary depending on your data collection software however it is important that the analog parameters GEN SCALE and Whisper User Manual The contents of the C3D files are easily viewed using the MLSviewer software from Motion Lab Systems web site http www motion labs com Whisper User Manual SCALE are correctly set to produce a calibration file output scaled in Volts as well will need to be able
8. Average current dissipation stand by mode 50 mA run mode 300 mA Output Impedance 22 Kohm 2 Common mode output level 1 0 1 0 Volt 5 Differential mode output level 2 048 2 047 millivolt 5 Table 5 Whisper technical specifications Whisper User Manual Appendix A2 e 65 Troubleshooting the Whisper The Whisper is a precision EMG signal generator and should give many years of trouble free service The following fault finding instructions are provided in the unlikely event that you experience problems with your Whisper The LED does not light when you switch on the Whisper Check that the batteries are not discharged Check that the batteries are placed correctly in the battery compartment see the illustration on aan Check the size of the batteries If you are using rechargeable batteries not recommended you may find that they are shorter then regular AA batteries This may give some problems The Whisper does not produce a test signal Check that the Whisper has been switched on and the LED is illuminated Check that the batteries are charged the LED will not turn on if the batteries are discharged Check that the LED on the power switch turns red orange as soon as you release the START switch Check that the START switch releases after being pressed if the switch sticks down then the LED will stay red orange and no output will be produced Check that at least one of the
9. COM and DIF mode switches was set on The Whisper only produces a differential output signal in Mode 0 or Mode 1 Check the connections between the Whisper and your EMG instrumentation Check that the Whisper and your EMG instrumentation have been grounded correctly Incorrect grounding could short circuit the test signal Check that your EMG instrumentation has been setup correctly and responds to an EMG level input The EMG signal does not look like EMG Check all the connections between the Whisper your EMG instrumentation and pay special attention to the ground connections Check that you are using an appropriate gain level for your EMG system and recording or data sampling equipment Check that you are using an appropriate sampling rate If in doubt use a rate close to 1 000 samples per second per channel If you are sampling multiple channels then the total sample rate must be increased appropriately The leading pulses in Mode 0 and Mode lare negative 66 e Appendix A2 The connection cable between the Whisper and your EMG instrumentation is not correct Disconnect the Whisper signal cable Figure 6lon page L and connect the cable the other way around Whisper User Manual Whisper User Manual The test signal saturates your EMG system Check all the connections between the Whisper your EMG instrumentation and ground Verify whether the connection cable between the Whisper and your recording EMG instrumentati
10. EMG recording level while maintaining a known gain for each EMG signal that is recorded The calibration procedure for fixed gain systems is very quick when using the Dataq Data Acquisition software All that needs to be known is the input range of the signal for a given channel gain setting in the case of an MA 300 EMG system this value can be read directly from the manual If the EMG system under test provides a channel gain factor rather than an input range then the input range can be calculated by dividing the output range of the device by the gain For a system with a gain of 8 000 and an output range of SV this figure would be 5 Volts 8 000 0 000625 Volt or 625uV peak This value can be used to set a fixed calibration for the EMG channel by entering the values as the positive and negative limits for the data in the Dataq Data Acquisition software Fixed Calibration High Calibrator Baseline FullScale Engr Yalue 0 000875 Low Calibrator Baseline Full Scale Engr Yalue 0 000875 Engr Units olt Cancel Figure 20 The fixed Calibration can scale the data directly in uV The Fixed Calibration is accessed via the F12 function key or via the Edit menu option Your ADC system is ready to record calibrated data in microvolts uV once this value has been set for each EMG channel that is to be tested Remember that a system with individual gain controls for each chan
11. Mode 3 recording with the results of a similar recording made when the Whisper is switched off Whisper Applications 18 e Using the Whisper The Whisper can be used to perform a number of different tests within any clinical gait or biomechanics laboratory e Multi channel equipment test e System performance test e System specifications test e System comparability test Each of these tests will be described shortly in the following sections The multi channel equipment test The goal of a multi channel equipment test is to compare the performance of a number of EMG channels in a measurement chain with each other This allows you to determine if the performance of any particular channel has changed or is different from another channel under test In general each EMG channel is a separate unit in the recording chain As a result errors or defects in an EMG instrumentation system tend to affect only one channel rather than every channel in the system A multi channel equipment test is therefore a useful tool to detect problems in individual EMG channels that might otherwise be missed Whisper User Manual In order to obtain a more precise measurement we can calculate a number of standard parameter values for each EMG channel By comparing these values to each other it is easy to draw evaluate your EMG channel performance Whisper User Manual In a multi channel equipment test the Whisper is connected to each EMG channel
12. common to use the date of the test as part of the filename so a typical set of filenames for a test would be 000618E1 C3D EMG test data recorded on 18 June 2000 000618C1 C3D CMRR test data recorded on 18 June 2000 000618N1 C3D Noise and offset test data recorded on 18 June 2000 n WINDAQ MA300 02 WDQ File Edit View Search Scaling Transform XY Options Help BEE uan lla 112 8 _i uv 875 0 iii Be ee ee O a a a a biol MID a am off SEC TM off EOF E 06 29 00 10 56 57 4 Figure 24 EMG showing the first 5 timing pulses The raw data files can be reviewed using any suitable data file viewer the contents of C3D files may be checked using software supplied by your data capture system A Whisper Tutorial e 35 manufacturer or by using the Mia de available from Motion Lab Systems web site at pttoAwww com Data recorded using Dataq software can be viewed using WINDA0 browser software A quick check of the start of any Mode 0 or Mode 1 test should produce an EMG data display similar to that shown in it may be necessary to adjust the horizontal time base to view the en Converting the data DST files use a standard file format developed by CAMARC in the 1980 s Detailed information on the file format and the various lexicons is available from the Motion Lab Systems web site http www motion labs com At the time of writing RData2 supports the generation of Whisper DS
13. for Whisper output Viewing the Whisper DST file The EMG Equipment Tester software can be run once a DST file has been created This software application provides the ability to view via the Quickview option the contents of any suitable DST file However if the DST file contains data or parameters that are out of the expected range then the EMG Equipment Tester software may have problems opening and viewing the data This type of problem typically occurs if the DST file has been created with the wrong format or scaled incorrectly so that it contains data that is outside the range that the software is expecting to analyze A Whisper Tutorial e 39 40 e A Whisper Tutorial MisViewer 951001e1 dst of x A File Edit View Window Help 18 x x E amp x Close Print Preview Print apy Sections lab EXPeriment IDST 1 0 EXP 1 0 29 09 95 Enschede AdeSampleRat ExPeriment SA a AdcS ampleR ate ab EmgPreProcessing EmgPreProcessing ab EmgUnits EmgUnits AdcRESolution AdcRE Solution EMG IEMG 4 For Help press F1 Figure 27 MLSviewer can display the DST file structure parameters and file header ML Sviewer is a general purpose DST file viewer that can open almost any DST formatted file and display the contents of the header and all parameters and data within the file This application can often be useful if the EMG Equipment Tester software fails to open a new DST file for any reason 756 00
14. from the recordings and compare the values of these test parameters with each other Differences between test parameter values can only be attributed to differences in the EMG instrumentation in both laboratories If you conclude that the output of the instrumentation of the separate laboratories is different you may conclude that the equipment is functionally different and that data recorded and processed in these two laboratories may not be directly comparable If you conclude that the output of the separate EMG instruments is the same then you can consider this as a reasonable indication that the equipment is functionally similar and that the data recorded and processed in these two laboratories may be directly comparable Whisper User Manual A Whisper Tutorial Introduction The Whisper can also be used as a quick check of an EMG system by simply reviewing the output of a Mode 0 EMG test signal via any convenient display device such as an oscilloscope or analog signal monitor Whisper User Manual It is very simple to record EMG test data from the Whisper but care must be taken to ensure that all the parameters of the recording are carefully controlled in order to produce meaningful results This chapter will illustrate this using a pair of different EMG systems Motion Lab Systems MA 100 and Motion Lab Systems MA 300 EMG systems together with a Dataq analog data acquisition system on an IBM compatible PC 100MHz 486 with Windo
15. in the Control Window allows you to return to the Main screen to switch to Spot Check option or exiting the application if you wish Spot Reco Figure 31 Spot Record Analysis screen of the EMG Equipment Tester Whisper User Manual When using the browse file selection method the open window will only display data files with the appropriate file type in this case only dst filenames will be shown Quickview allows you to easily check that all the channels have recorded the standard test signal in the same Way Whisper User Manual The default Spot Record Analysis option is Quickview and this is the option that is initially displayed on the selection button in the Spot Record Option Clicking on this button will display a menu that allows you to select one of three possible Spot Record Analysis options Quickview Spot Record Analyzer and Report Generator Viewing a file in Quickview If you select Quickview in the Selection window the File Information window will contain a single file request dialog Enter the name and the path of the file that you want to view by typing it directly into the space provided or use the control on the left of the dialog box to open a window and browse for the file For the purposes of this tutorial select the file 95 00 e1 dst which has been installed in the data sub directory To select the file you must click on the file and then click the open button The EMG Equipment Tester software
16. is able to show you the overall performance of up to four EMG channels This means that you have to develop a connection board that can be used to connect the output of the Whisper to four EMG channel inputs simultaneously In case of a bipolar EMG instrument a full Equipment Test consists of three recordings mode 0 mode 2 and mode 3 In case of a mono polar EMG instrument the full Equipment Test consists of only two recordings mode 1 and mode 3 After you have made the recordings and transformed the data in the appropriate data format you present them to the EMG Equipment Tester software Before you are able to analyze them you should verify in Quickview whether the EMG file mode 0 mode 1 and the Common Mode file mode 2 are indeed suitable to be analyzed If this is the case you can start the analysis We recommend doing this analysis using the Spot Record Analyzer Report Generator If your EMG recording system records raw EMG you can select all five parameters to view test If your EMG system records smoothed rectified EMG it is useless to select Frequency parameters and the Common Mode Rejection Ratio As soon as the analysis has been done you can compare the behavior of your EMG recording instrument with a previous recording We recommend doing this with the Spot Check Report Generator After this check the full Equipment test has been done and the EMG Equipment Tester software can be left At the R R D laboratory in Enschede
17. pre amplifier body and connecting the separate ground lead to the green DIN connectors on the subject back back This is illustrated in Figure 8 fn page a Whisper User Manual Because the signal levels generated by the Whisper are very low it is essential that all the equipment used in the test is grounded and shielded Whisper User Manual Checking the Signal Levels If this is the first time that you ve made a recording using the Whisper then you may want to connect up the system and try a few trial recordings to check that you have the Whisper EMG Out cable polarity correct The correct signal is shown in 14 where the five leading pulses in a Mode 0 or Mode test signal are positive going signals although you may see some overshoot of the signal depending on your EMG system characteristics In general the positive leading edge of the signal will have a greater amplitude than the ve going overshoot Figure 14 the five leading pulses of a Mode 0 or Mode 1 signal should be ve For first time recordings it is also a good idea to make a trial Mode 0 or Mode 1 recording and check that the recorded signal levels are correct the Whisper EMG test signal should be clearly seen and should utilize a significant portion of the ADC input range as shown in Figure 14 the EMG system gain is set correctly and the analog data acquisition system is setup correctly There are two possible problem areas with the EMG
18. test signal at this point the gain may be too high or it may be too low In each case you should check that the analog data acquisition system is set up for the expected EMG system output range before adjusting any part of the EMG system Both the MA 100 and MA 300 EMG systems used in this tutorial have user adjustable gain controls and these can be adjusted if necessary to produce a good test signal Figure 15 Too much gain causes signal clipping A Whisper Tutorial e 25 Gain Calibration 26 e A Whisper Tutorial Whisper will be clipped as shown in Figure 15 note the extremely flat appearance of the EMG signal This produces distortion of the test signal and will cause the EMG testing software to produce erroneous results that do not accurately reflect the system performance Signal clipping can be caused by an incorrect choice of data acquisition input levels as well as by the selection of too large an EMG channel gain If the EMG system gain is set too high then the EMG test signal generated by the If the EMG system gain is insufficient then the EMG signal will appear to be very low as shown in While this is not so much of a problem as having too much gain it is still not an optimal situation for either day to day operation of your EMG system or testing with the Whisper EMG system If your EMG system has variable gains for the EMG channels then you should increase the gain to try and obtain a signal close
19. the frequency response of the system to match the analog recording system or filter the EMG signal to remove noise and other artifact before recording and measurement High Pass Filters If the EMG system contains variable High Pass filters these remove low frequency artifact components from the raw EMG then they should be set to the lowest frequency setting available The MA 100 contains a variable High Pass filter that is controlled via a connector on the rear of the unit CONTROL or via an optional switch box The filter should be set to the minimum value of 20Hz The standard MA 300 system does not contain a High Pass filter so this setting can be disregarded unless you are using the optional High Pass filter or an external filter In either case the High Pass filter should be set to the lowest frequency available or turned off Whisper User Manual Whisper User Manual Low Pass Filters If the EMG system contains variable Low Pass filters these remove high frequency noise and other components from the raw EMG signal then they should be set to an appropriate value Figure Tallone the spectral content of the test signal generated by the Whisper and demonstrates that the signal does not contain any components above 300Hz If you only consider the spectral response of the EMG signal then you could choose a Low Pass filter point that is too low and removes part of the Whisper test signal 0 30 60 90 120 150 180 210 240 270 300 Figur
20. timing may be seen halfway between pulse and includes a common mode component Select Whisper Mode 1 to generate the last timing pulse and the a test signal that does not contain any common mode signals this is useful if you start of the EMG signal this are testing an EMG system that has a mono polar input or has a very low common is normal and can be ignored mode rejection ratio I i ay PRG Chan Figure 23 Whisper timing pulse 20Hz 500Hz bandwidth The following items are good indicators of a quality EMG test recording using a test signal generated by the Whisper in either Mode 0 or Mode 1 34 e A Whisper Tutorial Five positive going timing pulses should appear at one second intervals prior to the start of an EMG signal The amplitude of the timing pulses is not critical as this will be affected by the frequency response of the system under test If the timing pulses appear to be negative then you will need to reverse the EMG signal connections to the inputs of the device that is being tested The EMG signal should start one second after the last timing pulse and last for fifteen seconds followed by a quiet baseline signal If you have Whisper User Manual You must use the correct file name format for your EMG data files if you wish to use the EMG Equipment Tester software to analyze the data Whisper User Manual recorded five timing pulses then this will require a recording that is at least
21. twenty two seconds long e The EMG signal should be clean and should not clip at the maximum and minimum recording signal range There should be no significant difference in EMG amplitude between a Mode 0 and Mode 1 EMG test signal If you find that Mode 0 EMG test signals are very large while Mode signals appear to be much lower in amplitude then the equipment under test may have a common mode problem e The peak EMG signal amplitude should be approximately Once you have established that the signal generated by the Whisper appears to be appropriate for testing the system you will need to make three separate data recording for the EMG testing software These will normally be e Mode 0 five timing pulses followed by fifteen seconds of EMG with a common mode component e Mode 2 fifteen seconds of common mode signal without any EMG signal e Mode 3 ten seconds of baseline without and common mode or EMG signal If you are testing an EMG system that does not have a differential input and cannot reject a common mode signal or has problem with large common mode inputs then you should substitute a Mode test for the Mode 0 test If you want the EMG testing software to automatically recognize the file types then you should choose file names that end in En for Mode 0 tests EMG Cn for Mode 2 tests CMRR and Nn for Mode 3 tests noise offset where n is a number from 0 to 9 that can indicate the test number for multiple tests It is
22. will then select this file for display and will cause the Start Analysis button to appear at the bottom of the control window If any problems are detected in the selection procedure then the Message lt Not A Path gt will appear in the File Information dialog box If this happens the Start Analysis button will not appear In that case you have to repeat the file selection procedure until the file has been selected Look in amp data 7 l gl Sle e 951001c1 dst 157KB Data Storage and Transfer 29 Sep 95 2 12 AM a 951001e1 dst 365KB Data Storage and Transfer 29 Sep 95 2 12 AM e 951001n1 dst 104KB Data Storage and Transfer 29 Sep 95 2 12 AM ea Emgtste1 dst 77KB Data Storage and Transfer 07 Nov 99 2 48 PM ea Eprom_el dst 100KB Data Storage and Transfer 07 Nov 99 2 51 PM DI f951001e1 dst Files of type Custom Pattern dst x Cancel File name Figure 32 The file open dialog Once the file has been selected the EMG Equipment Tester software is ready to view the data contained within file Click Start Analysis to start the Quickview option The selected EMG data file will then be loaded and the Quickview screen displayed After a brief pause depending on your CPU and computer speed four graphs will be drawn on the screen The demonstration file that you have selected contains raw EMG data recorded from a four channel equipment test Therefore you will see four graphs in the Quickview screen as soon as the da
23. 12 by default when RData2 is installed If your data collection hardware is not a 12 bit resolution system then you must change this value to reflect your specific ADC capabilities The menu allows you to enter some information about the location of the testing site a serial number and a description of the testing configuration This information is saved in all Whisper formatted DST files and can be used for quality control and configuration purposes Full details of these header options can be found on page 57 inhi chapter on eile oai Using RData2 It is a simple process to generate the files required by the EMG Equipment Tester software once RData2 has been registered and configured to generate DST formatted files using the Whisper lexicon The process is very simple and consists of opening the raw EMG data file and then saving the file this process automatically exports the data to a DST format file with the same file name in the same directory as the original data file The original data file is unchanged You can use the Save As option to change the file name and the location of the exported data and change the type of data file that will be written out RData2 can be closed once you have converted all the raw Whisper data files to DST file The resulting DST files can be viewed using the MLSviewer software available from Motion Lab Systems and can be opened by the EMG Equipment Tester software Note that for C3D files and Data
24. 600000E 1 0 000000E 0 1 100000E 1 9 000000E 0 9 000000E 0 0 000000E 0 8 000000E 0 9 000000E 0 9 000000E 0 0 000000E 0 1 100000E 1 0 000000E 0 6 000000E 0 0 000000E 0 0 000000E 0 0 000000E 0 5 000000E 0 9 736605E 1 9 674984E 1 9 703971E 1 9 673129E 1 4 000000E 1 4 000000E 1 4 000000E 1 4 000000E 1 1 937604E 0 1 892821E 0 1 895600E 0 1 859045E 0 3 582031E 2 833984E 1 171875E 1 2 051758E 64 e Appendix A1 Whisper User Manual Appendix A2 Technical Issues Service and Support The Whisper and the EMG Equipment Tester software are guaranteed and supported for one year from the date of purchase This means that in case of problems and questions you can always contact us by mail phone fax or e mail It is suggested that US customers who purchased the Whisper through Motion Lab Systems should first contact Motion Lab Systems to resolve any problems Please mention the serial number of your Whisper when you contact us US distributor Motion Lab Systems Inc 4326 Pine Park Drive Baton Rouge LA 70809 USA Tel 1 225 928 4248 Fax 1 225 928 0261 e mail support motion labs com Internet ittp www motion labs com Manufacturer Roessingh Research and Development Roessinghsbleekweg 33 7522 AH Enschede The Netherlands Tel 31 53 4875777 Fax 31 53 4340849 e mail Internet http www rrd nl Electrical Specifications Power Source 4 AA batteries 1 25 Volt 500 or 720 mAh
25. Motion Lab Systems Whisper User Manual Distributed by Motion Lab Systems Inc MOTION LABHSKX SYSTEMS Whisper User Manual Published February 2001 Revision 1 51 Intended AudienceThis manual is written for anyone using the Roessingh Research and Development Whisper EMG Test Set It is assumed that the user is familiar with the principals of the Electromyography equipment that they use and any associated EMG data collection system Separate manuals for these products are available from their manufacturers The following are registered trademarks Whisper Roessingh Research and Development Windows 98 Windows NT Microsoft Corporation RData2 Motion Lab Systems Inc Y2K compliance statement The Whisper is Year 2000 compliant It will not produce errors in date data related to the year change from December 31 1999 to January 1 2000 It will handle leap years correctly All MLS products either do not use internal date codes or utilize specific non ambiguous representation handling and interpretation of centuries Electrical Safety The Whisper is a battery operated electronic signal source that generates a sequence of test signals that simulate some characteristics of an electromyographical EMG signal The unit is not designed to perform any electrical safety tests on your EMG system or replace any subject safety tests that are performed by a biomedical engineer
26. Rejection Ratio CMRR of the EMG instrument under test in dB e The frequency of the recorded common mode signal in Hz Both parameters are calculated from the Common Mode file a Whisper Mode 2 recording Two seconds of data is extracted from the middle of the file ten to twelve seconds after the start of the recording and used to calculate the Power Spectrum of the data The frequency at which the Power Spectrum is maximal is determined first Since the common mode signal is a pure 40 Hz sine wave the maximal frequency should also be 40 Hz This is displayed as the estimated frequency of the recorded common mode signal Once the maximal frequency has been determined the common mode signal can be reconstructed from the same two seconds of Common Mode file data by first performing a Fast Fourier Transform FFT on the signal The FFT signal is then bandpass filtered bandwidth 25 of F mode around F mode and from this signal the Inverse Real FFT will be calculated This signal should be a 40 Hz sine wave The Whisper generates a known 1 0 volt common mode signal during a Mode 2 test Since we know the amplitude of the common mode signal at the input of the EMG instrument the Common Mode Rejection Ratio can be calculated by dividing 1 0 by the estimated amplitude and taking the 20 log of this result Noise Offset parameters e The RMS noise of the EMG instrument under test in microvolts e The DC offset of the EMG instrument under test
27. T files from C3D files Motion Analysis Corporation ANA files and Dataq ADC files only 36 e A Whisper Tutorial The EMG Equipment Test Software supplied with the Whisper requires that the data files submitted to it are in DST format This is a standard ASCII text file format that can be used to describe a broad range of data with the exact format of the contents of a DST file being specified by a lexicon In this case the Whisper lexicon describes a header that must exist at the start of the file to provide some basic information about the test situation while the test data is stored as a series of integers with a count of 1 representing one microvolt An example of this format can be found on page 63 in Pippendix Alt the end of this manual If your data recording and collection system produces data in this format then you can immediately start using the EMG Equipment Tester software supplied with the Whisper However while the DST format commonly used for storing processed data it is not widely used to store raw data so we must usually convert the recorded EMG data from the Whisper before we can use the EMG Equipment Tester software to analyze the information and produce a report Many common file formats including C3D and Dataq CODAS formats can be converted by RData2 an ASCII software conversion tool that is included with your purchase of the Whisper from Motion Lab Systems RData2 can read many common binary biomechanics data formats
28. amplitude parameters reliably it is important that the RMS and Mean values are measured correctly from the EMG portion of the recorded signal If the five leading pulses and the recording system sample rate have been determined it is simple to locate the start of the EMG signal since it starts exactly one second after the last leading pulse and is exactly fifteen seconds long By calculating the RMS and Mean values of the fifteen seconds of standard EMG test signal in a Whisper Mode 0 or Mode 1 recording you can determine the gain and DC offset parameters of the EMG instrumentation and data recording system under test Frequency parameters An EMG recording instrument can be regarded as a chain of filter and amplifier stages In general the settings of these stages can be changed gain cutoff frequencies bandwidths etc Each of these stages has its particular task and together they ensure that an EMG signal will be recorded without distortion with minimum noise or disturbances and maximum common mode rejection The power spectrum of the standard test signal produced by the Whisper is known and consequently the value various frequency parameters of the power spectrum Fmed Fmode etc are known In order to be able to record the EMG signal without distortion the bandwidth of the EMG power spectrum has be equal to or preferably less than the bandwidth of the whole recording chain By calculating the frequency parameters of the recorded EMG si
29. and generate a wide range of ASCII output data including DST file using the Whisper lexicon Configuring RData2 The RData2 application from Motion Lab Systems Inc is supplied with its own user guide and registration information and must be installed separately from the Whisper EMG Equipment Tester software The registration information provided with your copy of RData2 must be entered as described in the RData2 User Manual before you can use the application to generate DST formatted data files suitable for analysis Once the RData2 application has been registered you will need to specify the DST lexicon to be used RData2 supports several different lexicons and customize it with information about your testing environment and location Selecting the Whisper Lexicon Start the RData2 application and select Defaults from the Export menu and choose the DST Export option tab In this tab you will find the Lexicon option which will initially default to MLS Click on the Lexicon option until it displays Whisper Rdata2 will now default to producing DST files using the Whisper lexicon whenever a data file is exported DST files generated using the Whisper lexicon will have a specific file header and contain EMG data scaled in microvolts uV An illustration of this file lexicon can be found in this manual in Appendix A1 pn page Whisper User Manual Analogue Data Scaled Video Data Scaled Show Residual Show Mask fae Pr
30. any pre amplified electrode When testing any EMG system that uses pre amplifiers you must connect the Whisper EMG test set directly to the electrode disks that are normally placed on the subjects skin If you are testing an EMG system that uses passive electrodes then you must connect the Whisper directly to the EMG system inputs that would normally connect to Gel or other passive electrodes on the subject A Whisper Tutorial e 21 22 e A Whisper Tutorial System Gain Both the MA 100 and MA 300 systems support a range of different gain settings for each EMG channel The MA 100 EMG system uses an individual variable potentiometer gain control for each EMG channel on the back pack to allow the user to adjust the EMG level that the system detects on the subject This gain control is adjusted by the user to record an optimum maximal EMG signal on each channel as determined by the individual LED displays As a result the channel gain control must be set by generating a Mode 0 EMG test signal from the Whisper and adjusting the gain control so that the maximal signal is recorded without overloading the system Once the gain control is set the precise channel gain can be calculated by making a test recording from the internal calibration source built into the MA 100 back pack The MA 300 EMG system uses preset switches to determine the individual channel gains Channel gain settings are marked in terms of the maximum peak to peak input that can b
31. appropriate DST data format and name the file according to the following format YYMMDDeN DST e Run the EMG Equipment Tester software e View the file in Quickview and be sure that you have recorded the 5 leading pulses and that the first and only the first leading pulse occurs in the first 2 seconds of the recording If both criteria are satisfied your file is suitable to be analyzed by the EMG Equipment Tester software Common Mode Test Protocol Mode 2 The test protocol for Common Mode can be used to measure the Common Mode Rejection Ratio of your EMG instrumentation e Connect the Whisper to your EMG instrumentation e Setup your EMG recording instrumentation such that it can record the standard test signal without saturating during at least 15 seconds e Select only the common mode signal of the simulator by switching the COM switch on and the DIF switch off e Switch the Whisper on e Push the Start Button and start recording the EMG data within one second Write the data that you have recorded in the appropriate DST data format and name the file as follows YYMMDDcN DST e Run the EMG Equipment Tester e View the file in Quickview and be sure that you don t see the 40 Hz sinusoidal signal during the first 6 seconds of the recording and that the 40 Hz sinusoidal signal is present during the 10th 12th second of the recording If both criteria are satisfied your file is suitable to be analyzed by the EMG Equipme
32. art generating an EMG test sequence as soon as you push the START button located to the left ofthe POWER switch You will need to start your EMG recording system at the same time as you press the Whisper START button With the Whisper turned on and the power LED green press the START button on the Whisper and start you EMG data collection recording system The LED above the Whisper power switch will turn orange red and your EMG recording instrument will record a standard EMG test signal from the Whisper for the next twenty two seconds At the end of the EMG test sequence the Whisper LED turns green again and you can stop your recording device and store your data Whisper User Manual Whisper User Manual Figure 9 The standard test signal recorded by raw EMG instrumentation Once you have completed an EMG test recording you can view the recorded EMG data using your normal methods If your EMG instrumentation records raw EMG then your recording should look like the signal that is shown in If your EMG instrumentation records a rectified and filtered EMG signal also called envelope EMG then your recording should look like the signal that is shown in Figure 10 Both illustrations show highly compressed EMG signals to illustrate the entire EMG test sequence each illustration covers a period of about twenty two seconds Figure 10 The standard test signal recorded by envelope EMG i
33. at mates with the black ground reference jack on the left of the EMG OUT connector while the other end has a standard safety DIN connector Figure 7 The Whisper ground reference cable The ground reference cable should be connected to the to the grounded input of your EMG measurement chain normally the EMG ground or indifferent reference Installation e 5 The standard Whisper test signal starts with 5 leading pulses that check the recording system polarity When the Whisper LED is green the unit is ready to start generating an EMG test signal It s a good idea to turn off the Whisper when you have finished an EMG test to preserve the batteries 6 e Installation connector The EMG signal cable is connected to the input of your EMG measurement chain The EMG signal cable is supplied with two simple spade connectors that are suitable for most common EMG surface preamplifiers You may need to modify this cable if your particular EMG input device does not interface to these connections The EMG signal connector has a positive and negative lead The cable should be connected in such a way that the red lead on the EMG signal cable is connected to the positive input of the EMG system If you don t know which of the inputs of your EMG instrument is the positive one then connect the cable in the most convenient manner A test will be described later that will check that the EMG signal cable has been connected correctly spe e
34. bserved in a single test signal The differential mode signal The differential mode signal consists of five leading pulses followed by fifteen seconds of standard EMG generated from a signal stored in the Whisper EPROM s The pulses are spaced 1 second apart Their duration is one millisecond their amplitude is 500 uV There is one second between the release of the START button and the first pulse and one second between the fifth leading pulse and the stationary EMG signal The stationary EMG signal is fifteen seconds long The Whisper stops one second after the stored EMG signal has finished Figure 11 khows a sample of the differential mode EMG signal while Figure 9 fillustrates the entire fifteen second sequence Figure 11 Differential mode EMG signal The differential mode EMG signal that is stored within each Whisper is a simulated signal so that it has a precise amplitude and known frequency components This avoids the problems inherent in recording a long continuous burst of EMG from a human subject In Frequency parameters of the myoelectric signal as a measure of muscle conduction velocity IEEE Trans Biomed Eng Vol 28 1981 p 515 523 Stulen F B and De Luca C J show that a stationary EMG signal can be obtained by band pass filtering a white noise random sequence The fifteen seconds of EMG used by the Whisper were obtained by low pass filtering and then high pass filtering fifteen seconds of
35. by simply comparing the corresponding results in two different results files Thus the quality of an EMG system can be checked on a regular basis by comparing data from tests made several days or weeks apart For example by examining two results files that have just loaded you could conclude that the performance of the EMG instrument under test has not changed since both Results files contain very similar test values As soon as you have compared two result files the Spot Check has been completed You can leave the Spot Check screen by clicking on the Exit button If you click on Exit to Main and on Quit then you will leave the EMG Equipment Tester software and return to the Windows operating system The EMG Test software e 55 Whisper User Manual 56 e The EMG Test software Whisper User Manual File Descriptions Protocol standardization Whisper User Manual The EMG Equipment Tester software has been developed to automate the analysis of standardized EMG test signals generated by the Whisper EMG signal generator It analyzes recordings from the output of EMG system instrumentation using an automated standardized procedure that is guaranteed to be repeatable at any time EMG instrumentation can be tested at any time and in any location with the certainty that the results of the tests can be compared in a meaningful way In addition to the basic quality assurance features of the Whisper the instrument also allows users of EMG instrume
36. cal EMG test report generated using Whisper test data The Whisper package supplied by Motion Lab Systems includes two software tools to help the user analyze their recorded EMG signals The EMG Equipment Tester software written by Roessingh Research and Development which performs the EMG test signal analysis and also generates a report of the Whisper test results The package also includes RData2 a file translation application from Motion Lab Systems that generates the DST files required by the EMG Equipment Tester software from C3D and Dataq binary data files The Whisper is CE marked The CE mark is the official marking required by the European Community for all electronic equipment sold or put into service for the first time anywhere in the European community It proves to the buyer or user that the Whisper fulfills all essential safety and environmental requirements as they are defined in the European Directives Electrical Safety The Whisper is a battery operated electronic signal source that generates a sequence of test signals that simulate some characteristics of an electromyographical EMG signal The unit is not designed to perform any electrical safety tests on your EMG system or replace any subject safety tests that are performed by a biomedical engineering safety check Testing an EMG system with the Whisper must be in addition to your regularly scheduled safety testing and is not a substitute for regular biomedical equ
37. calibrated in Volts the 5 Volt range is shown on the left side of the display The cursor has been moved to measure the maximum signal present in the display Ctl K using the Dataq software and this value 1 5759 Volts is displayed in the center of the range display on the left We can use the built in calibration function of the Dataq software Function key F11 or assessable via the Edit menu to scale the signal We know that the input signal is 200uV RMS and that the output signal is 1 5759 Volts Peak High Calibration Input Level 1 5759 Volt High Cal Value 282 88 Engr Units uY Figure 18 Dataq peak level calibration Applying the RMS conversion factor 1 4144 give us a peak input signal of 282 88uV so we can use the Dataq Browser software to directly re scale the recorded signal and display the new data units This is done by entering a High Calibration value that is equivalent to the peak value of the input signal and changing the Engr Units display to uV y7 WINDAQ MA100CAL WDQ BE File Edit View Search Scaling Transform XY Options Help M off EOF E JE MID sa SEC TBF SEF SEC T Figure 19 The Dataq Browser calibrated in uV Since the MA 100 EMG System has individual gain controls on each channel this procedure must be performed on each channel that is to be evaluated using the Whisper Once the High Calibration has been performed the Dataq Browser softwa
38. d EMG signal you should select an analog sampling rate that is at least double the minimum required If at all possible you should set your analog recording system to sample the EMG data at a rate of at least 1800 to 2000 samples per second to provide a signal bandwidth of 900 to 1000Hz in practice A Whisper Tutorial e 23 Preparing for an 24 e A Whisper Tutorial Sampling Characteristics There are a wide range of different sampling techniques and methods and it is important to understand the different options that your ADC card offers in order to generate clean and accurate data recordings Many of these options are unique to particular manufacturers or data collection cards so it is quite possible that you may have additional options to those discussed below In addition many inexpensive ADC cards offer only a simple interface without any of these options Oversampling Many Analog Data Collection systems allow you to sample the analog data at very high rates often much higher than you would normally record the sampled data This is a very useful feature that allows the ADC card to provide some measure of anti alias filtering of the input data as the system can process a larger number of analog samples to generate a single sample for recording Oversampling usually offers a number of options for selecting a data sample e Average a number of data points are averaged together to generate a sample data point This method is very ef
39. d email address can be found at the front of this manual Setting up and testing the Whisper The Whisper is powered by four AA alkaline batteries supplied these are easily obtained at any hardware store If you plan to make extensive tests with the Whisper then you may want to purchase additional batteries Installation e 3 4 e Installation Start by examining the Whisper and becoming familiar with the layout of the front panel connections and controls Figure 3 The Whisper front panel The front panel of the Whisper is simple from the left to right you find e EMG Ground Signal Reference e EMG Signal Output e Differential Mode Signal On Off Switch e Common Mode Signal On Off Switch e Start Button e Power On Off Switch e LED indicator Simulator On Off Active The rear of the Whisper provides access to the battery compartment Figure 4 The Whisper back panel showing the battery compartment Start the installation by checking that the POWER switch on the front of the Whisper is in the off position The battery holder can be removed from the back of the Whisper by pressing the two clips together in the direction shown by the two arrows gt Vi 5 O iE he in g Li LU 2 m a lt A ALKALINE BATTERY PA ETENA ANNIVOIV ITEP ELE Figure 5 The Whisper Battery pack Whisper User Manual LEMO p n FGG OB 302 CLA D45 Z w GMA OB 045 D6 Whisper User Manual Remove the batt
40. d values These gain factors are called GEN SCALE and SCALE There is a single GEN SCALE parameter that is applied to every analog channel the value of the GEN_SCALE parameter is usually set when the data capture system is installed Since this scale factor is applied to all analog data it is usually not changed very often we will need to know its value but will not change it when we calibrate our individual analog channels The calibration for each analog data channels in a C3D file is controlled by an SCALE factor parameter this parameter has an individual value for each channel that is directly related to the gain or input range of the channel in combination with the GEN _SCALE value While the GEN_SCALE and individual SCALE parameters can take any value it is normal to choose these parameters such that results in the analog channel are scaled in some known value normally this will default to Volts The C3D analog parameter UNITS should normally describe the measurement system for each channel Common values for GEN SCALE are e 0 0048828 the value of a single bit of data from a 12 bit ADC that is measuring a 10V input range An individual channel SCALE value would then be 1 00 to obtain the analog data scaled in Volts e 0 0024414 the value of a single bit of data from a 12 bit ADC that is measuring a 5V input range An individual channel SCALE value would then be 1 00 to obtain the analog data scaled in Volts e
41. dal signal with an amplitude of 1 00 Volt at a frequency of 40 Hz This common mode signal remains present for fifteen seconds and then returns to 0 0 Volt during the last second of each simulation The common mode signal is stored in the same way as the differential mode signal and is also converted on a one to one basis to each differential output of the Whisper EMG signal specifications Whisper User Manual The standard EMG test signal used by the Whisper to test the performance of your EMG recording instrumentation has the following characteristics These can be verified from the file EPROM_e1 DST that is installed in the data subdirectory to the EMG Equipment Tester software A full description of the format of this file is given in File Descriptions later in this manual EMG signal RMS Value EMG signal Mean Value Leading Pulse Width Leading Pulse Amplitude Common Mode Amplitude w eT Common Mode Frequency Table 1 Standard Test signal values e RMS value indicates the Root Mean Square value of the fifteen seconds of digitized EMG signal e Mean is the mean value of the 15 seconds of digitized EMG signal e med is the median frequency of the power spectrum of the first two seconds of the digitized EMG signal e Fmode indicates the frequency at which the power spectrum of the first two seconds of the digitized EMG signal is at its maximum e Pulse width and Amplitude refer to the 5 leading pulses The i
42. distributed with the Motion Lab Systems MLSviewer application that is available from the web site http www motion labs com 58 e File Descriptions In order to be able to analyze your test data with the EMG Equipment Tester it is necessary to write your data in the appropriate data format The format which will be used is an ASCII text format and origins from the CAMARC II DST EXP lexicon This means that each test data file should have a header in which the kind of test data will be described followed by the actual test data The following shows an example of such a header followed by the first 5 data lines of a test data file DST 1 0 EXP 1 0 01 10 95 Enschede SEXPeriment EMG source Whisper TM serial number RRD CES 9412 01 Equipment under test 8 channel EMG amplifier Employee performing test BF Date of test 01 10 95 Test sequence starts at 13 24 Channels tested 1 2 3 4 AdcSampleRate 1024 SEmgPreProcessing raw SEmgUnits microvolts AdcRESolution 12 EMG 4 7 8 3 I x 2 7 9 go 3 1 4 5 4 di 12 14 1 12 8 This header is provided in the data directory as the file HEADER TXT I you are generating DST files using a text editor it is recommended that you copy this header to the start of the file above your test data and then change the information in the header so that it matches the recorded data In order to be able to edit the header in the appropriate way you shou
43. e 3 gain setting is selected because this is the optimum input range on an MA 300 system for the Whisper tests which generate an EMG signal in the range of 742uV to 670uV A higher gain setting would cause the Whisper test signal to exceed the input range of the EMG system under test see Figure 15 pn page P5 for an example of this type of problem The individual SCALE value for the EMG channels can be determined from information provided with the EMG system user manual or calculated directly as follows ADCrange resolution ADCgain EMGgain GENSCALE SCALE Where EMGgain 5508 ADCrange 20 Volts ADCgain x2 5 volt range resolution 4096 12 bit resolution Whisper User Manual Thus 20 0 20 0 SCALE 0 0000004 4096 2 0 5508 0 4096 2 0 5508 0 1 0 The EMGgain figure is the total amount of amplification applied to the signal from skin surface to output of the EMG system as applied to the input of the ADC If any additional signal processing equipment is placed in line between the EMG system output and the ADC data sampling system then the gain if any of this item must be included in the EMGgain figure Note that the gain figure used here is a nominal gain due to component tolerances this figure may vary from the typical quoted gain value for a specific setting Consult your EMG system manual or equipment manufacturer for details of acceptable tolerances for this figure Note that the value
44. e 13 Whisper EMG spectrum Hz However the test signal generated by the Whisper also contains a number of short timing pulses that are also affected by this filter setting As a result it make sense to choose a higher filter setting to avoid unnecessarily attenuating the five leading pulses that precede the EMG test signal A suitable setting for the internal MA 300 Low Pass filter would be 5 750Hz or 4 1 000 Hz while the MA 100 can be set to either 600 Hz or 1 300 Hz via an optional filter control box Some EMG systems do not have adjustable Low Pass filters in which case you can consider the entire EMG system to have a Low Pass frequency response that is equivalent to the maximum frequency that the system can reproduce You may need to consult the manufacturers literature to determine the exact bandwidth of the EMG system under test Choosing a Sample rate It is important to select a suitable sample rate to record the test signals generated by the Whisper In order to do this you must know the distribution of the signal spectrum that you intend to sample Figure 13 shows the spectral content of the test signal generated by the Whisper and demonstrates that the signal does not contain any components above 300Hz Given this information analog sampling theory dictates that the EMG signal must be sampled at a rate of at least 600Hz to prevent the generation of aliasing artifact in the recorded signal Since you intend to analyze the recorde
45. e applied for a given switch setting The MA 300 switch setting 3 indicates that this setting can handle EMG input signals of up to 875uV peak to peak This is the optimum input range on an MA 300 system for the Whisper tests which generate a differential EMG signal in the range of 742uV to 670uV ADC input range The analog recording system must be able to accurately record the signals generated by the equipment under test The maximum output signal generated by an MA 300 EMG system is 5 Volts which means that the recording ADC sub system must be set for a range that will handle signals of this amplitude Most common ADC sub systems will handle signals in the range of 5 Volts or 10 Volts Depending on the ADC system you may be able to directly select a range of 5 Volts or have a fixed range of 10 Volts and the option to apply a gain of x2 to provide an equivalent range The Dataq analog data acquisition system supports the sampling of analog data with a range of 5 Volts this is appropriate for the EMG signal levels that are produced by both the MA 100 and MA 300 systems Frequency Response It is important to consider the frequency response of both the Whisper test signal and the EMG system under test as both of these items will determine the minimum sampling rate that will be required from your data recording system Many EMG systems include a set of user adjustable filters that allow the user to tailor
46. e names of these files are shown in the File Information window Results File 990004 res Click on Exit to return to Spot Record Analysis Figure 35 The Spot Record Analyzer screen at the end of an analysis During an analysis these files are loaded and the selected parameters will be calculated and will appear on the screen The message box in the message controller window shows which task is under execution Since a complete test analyzes three files with lengths varying from ten to twenty two seconds each containing the data of up to four EMG instrumentation channels it can take up to several minutes before a Spot Record Analysis will be completed if you do not have a fast computer During a complete Spot Record Analysis performed with all three data files the following parameters will be calculated Amplitude parameters e The Root Mean Square RMS value of the recorded EMG signal in microvolts e The Mean value of the recorded EMG signal in microvolts Both parameters will be calculated over the fifteen seconds of data in the EMG file that contain the EMG signal The EMG data is located by first reading the file and looking for the five leading pulses The position of the five pulses within the file is measured and the average number of samples between successive pulses is calculated The Whisper generates these pulses at one second intervals so the average number of samples measured enables us to determine the EMG sam
47. ecision 3 orrect In addition to selecting the Whisper lexicon make sure that the Export option DST File is checked so that the application will produce DST format files and not plain ASCII text files Using RData2 with Motion Analysis data files In addition to selecting the Whisper lexicon Motion Analysis users who are recording data in the ANA file format will need to select an appropriate scaling factor for the data This is set in the MAC Selection tab in the options menu Whisper User Manual A Whisper Tutorial e 37 All of the data in the Whisper Information menu can be changed by double clicking on the item and entering the appropriate information A progress bar is displayed in the bottom status line of RData2 during all data export operations 38 e A Whisper Tutorial Entering your Test Information The final configuration option that is need is the information for the Whisper DST file header The only required item in this menu ADC Resolution is set by default to 12 a common value The remaining information is optional and can be entered as required via the RData2 Export menu selection Whisper Information Whisper Information x Data ltem TestSting Location MLS Serial Number Equipment Under Test Motion Lab Systems Inc MA 310 ADC Resolution 12 Figure 25 The RData2 Whisper Information menu The menu also contains a setting for ADC Resolution which is set to the value of
48. ery holder from the Whisper and insert the four AA batteries paying particular attention to the polarity of the batteries Once the battery pack is inserted firmly into the back of the Whisper you are ready to generate EMG signals The Whisper can be checked by turning on the POWER switch at the right side of the front of the unit The LED will glow green if the batteries have been inserted correctly Ifthe LED does not light up then check that the batteries are inserted correctly and that the battery pack has been firmly inserted into the Whisper If the batteries are inserted into the Whisper correctly and the LED lights when the power switch is turn on then you can test that the unit is functioning by turning the POWER switch on and pressing the START button located to the left of the POWER switch The LED will change from green to orange red as the Whisper starts to generate an EMG test sequence The Whisper is now operational Two cables are supplied to enable you to connect the Whisper to your EMG system you will need to connect both of them to you EMG system These are the EMG signal cable and a ground reference cable As Figure 6 The EMG signal cable with LEMO connector The EMG signal cable has a LEMO connector at one end that connects to the EMG OUT connector on the left side of the Whisper front panel The two output leads of the EMG signal cable have spade connectors The ground reference cable has a single connector th
49. eters the timing parameters and the dynamics of any bipolar EMG instrument can be tested this includes almost all common surface EMG preamplifiers Mode 0 applies a differential EMG signal to the EMG instrument under test and superimposes a common mode component over the EMG signal This tests the response of your EMG instrumentation to a differential mode signal in the presence of a large common mode signal Modern EMG preamplifiers should reject the common mode component and amplify only the differential EMG signal Mode 1 EMG only Mono polar EMG instrumentation often used with traditional needle electrodes not to be confused with fine wire electrodes can not reject common mode disturbances Therefore this mode does not include a common mode signal and only applies the differential EMG component during tests to determine the EMG parameters the timing parameters and the dynamical properties of the EMG instrumentation Mode 2 Common Mode Mode 2 allows testing of the Common Mode Rejection Ratio CMRR by applying a large common mode signal to both EMG signal lead simultaneously Since mono polar EMG instruments can not reject common mode disturbances this mode is only of interest for bipolar EMG systems Mode 3 Noise and Offset Mode 3 allows testing of the noise and offset properties and can be applied to any EMG recording instrument It does not produce any output signal other than the background noise level of the Whisper
50. etween two samples is more than the filter response time at least a few milliseconds the analysis software may not see every pulse e Check that the EMG signal gain is appropriate excessive gain can cause the software to detect an erroneous sample rate The Spot Analysis Report is missing some parameter reports for some channels in a multi channel analysis e Make sure that each Test data file contains the same number of EMG channels if you analyze an EMG file a Common Mode file and a Noise Offset file simultaneously Unexpected files appear in the EMG Equipment Tester directory e The EMG Equipment Tester creates some vi and rsc files under certain circumstances These files can safely be deleted after each analysis 68 e Appendix A2 Whisper User Manual
51. fective in removing high frequency noise from the sampled data that would otherwise appear as aliasing artifact e Last Point this simply returns the most recent data point as a sample e Maximum this returns the data point with the greatest amplitude as the sample point e Minimum this returns the smallest data point as the sample point When recording test data for use with the Whisper you will find that the Average and Maximum sampling methods produce the most accurate data The Maximum method will usually provide a better record of the five timing pulses when your data recording sample rate is low In general the Average method is the most appropriate for day to day EMG recording Differential Inputs Most Analog Data Collection systems offer the option to recording the data using a differential input this is generally only appropriate if the EMG system under test produces a differential output signal Most common ADC systems will use a single ended input arrangement EMG Test If you use an EMG system in regular day to day data acquisition then all you should have to do in order to make a recording is to connect the Whisper EMG Out cable to the two differential EMG inputs and connect the separate ground lead to a suitable ground connection on the EMG unit In the case of the MA 100 and MA 300 EMG systems used in this tutorial this means connecting the EMG Out cable to the pre amplifier inputs stainless steel disks on the
52. ferent recording situations e Stand alone tests using a Dataq ADC card recordings where the EMG information is recorded directly to a PC file Whisper User Manual Whisper User Manual e System tests using a Motion Capture system that generates a C3D file this is a common file format standard that is in use in many biomechanics and gait analysis laboratories worldwide Stand alone Tests This section will discuss the gain calibration of sample recordings made with the MA 100 and MA 300 EMG systems using a stand alone Dataq ADC card For the purposes of this tutorial these two EMG systems differ in their treatment of the signal in that the MA 100 system has a continuously variable signal gain while the MA 300 system offers a number of discrete switched gain levels While this example uses a Dataq ADC card the principals described here can be applied to almost any analog data collection system Variable Gain Systems The MA 100 has a continuously variable gain control for each EMG channel This allows the user considerable flexibility in selecting an optimal EMG recording level but means that the amplitude of the recorded signal is not accurately known Any variable gain system like this can be calibrated by applying a known input to the system and measuring the output level using the Dataq software The MA 100 includes a built in calibration source that generates an 87Hz sine wave calibration signal at a level that is equivalent t
53. files can be traced directly to errors in the file format or the scaling of the data The ML Sviewer is a very useful tool that can provide a great deal of useful information about any DST file as well as its built in ability to display the contents of industry standard C3D files Whisper User Manual A Whisper Tutorial e 41 42 e A Whisper Tutorial Whisper User Manual The EMG Test software Introduction This manual and tutorial uses as an example data from a Whisper EMG signal generator recorded and analyzed using an EMG amplifier in the R R D laboratory in Enschede the Netherlands The best way to avoid problems during installation is to read the manual before you start the installation Whisper User Manual The EMG Equipment Tester software has been developed by Roessingh Research and Development as a tool to analyze test records of EMG Equipment using the standardized EMG signals generated by the Whisper The software is able to view and analyze the data from up to four EMG channels simultaneously and displays the EMG common mode noise and DC offset parameters The software also allows the user to compare the current test results with any prior test results using the same equipment or with test results obtained in a colleague s laboratory As such it is not only possible to test the performance of your own equipment but it is also possible to compare the performance of your system with other EMG recording systems or envi
54. from the EMGEQTST INI file This message can be followed by another message that indicates the location of the memory conflict e Restart the computer and run the analysis again using fewer data files e Sample the EMG data at a lower sample rate if possible e Add more memory to the computer system that you are using The EMG Equipment Tester will fails to open a data file to perform an Analysis e Check that the data files are in the appropriate data format The EMG Equipment Tester will only open DST in the correct format You can use the MLSviewer from Motion Lab Systems to view the contents of a DST file and confirm that the format is correct e Check that you have named the data files in an appropriate format The EMG Equipment Tester will not open files that have names that do not conform to its naming convention e The EMG Equipment Tester does not open binary data files check that you data file is viewable in Quickview or MLSviewer The EMG Equipment Tester reports the wrong sample rate e Ifyou do not find the correct sample rate this can be due to your Mode 0 1 data file containing less than five leading pulses e Check the data file in Quickview or MLSviewer to make sure that the data file does not contain any unexpected spikes that could interfere with the software measurements e Check that your data collection sampling rate is high enough in comparison with the length of the recorded filter response If the time b
55. ftware e AnSVGA monitor and graphic adapter that supports at least 256 colors and a color printer supported by the operating system You can use the Windows Add Remove Programs option in the Control Panel to install the application from a floppy disk This will install the program on your system together with some example files that you can use to demonstrate the program If you accept the default options during installation then you will have created a short cut in the Gait Lab menu group called Whisper together with a desktop short cut and icon Getting Started The EMG Equipment Tester is the analysis tool which comes with the Whisper and was developed specifically to analyze the data recordings produced by the Whisper The analysis results from equipment tests can be stored in files on disk up to four EMG channels can be analyzed simultaneously Each stored analysis is informally known as a Spot Check and the results of the analysis are stored in a res file A sample results file called YOURSIM RES is included with the software and is documented in Appendix A1 The EMG Equipment Tester is able to compare two different res file analysis records with each other The Spot Check feature can be used to provide a history of EMG equipment tests of your EMG instrumentation as well as documenting the performance of your EMG instrumentation against the EMG equipment in another laboratory The structure of the EMG Equipment Tester softwa
56. g the following formula ADCrange resolution ADCgain EMGgain GENSCALE SCALE Where EMGgain Vout Vin 2 23 0 00028288 7883 ADCrange 20 Volts ADCgain x1 resolution 4096 12 bit resolution A Whisper Tutorial e 31 Warning At the time of writing Oxford Metrics Vicon Workstation applications have a bug that causes all SCALE factors of less than 0 000001 to be stored incorrectly Please contact Motion Lab system or your supplier if you encounter difficulties creating the correct SCALE values An Excel spreadsheet is available from Motion Lab Systems that documents the precise calculations needed to calculate C3D scale factors 32 e A Whisper Tutorial Using an ADCrange of 20 the ADC channel range is 10Volts an EMG system gain of 7883 Vout Vin and a GEN SCALE values of 1 00 yields a value of 0 00000062 for the ANALOG SCALE parameter to calibrate this channel in microvolts at skin surface You should change the ANALOG SCALE value in the C3D file to this value using the facilities provide in your C3D file creation software This calculation must be performed for each channel in the C3D file that is to be calibrated Note that this calculation should only be done for the EMG channels the ANALOG SCALE parameter for force platforms and other analog channels should not be altered without careful consideration of the effects of any change Normally the analog SCALE parameters are created wit
57. gnal produced by the Whisper it is easy to check that the various filter stages of the EMG instrumentation have been set correctly The frequency parameters are calculated from the first two seconds of digitized EMG signal this is generated in any Mode 0 or Mode 1 recording Once they have been measured the smoothed Power spectrum can be calculated Smoothing yields multiplication of the power spectrum with a Papoulis window The median and the mode frequency can be determined from the power spectrum Dynamic response In theory the impulse or dynamic response of any electronic system contains all the information about the dynamics of a system Any changes in the dynamic response of the system will change the shape of the impulse response The impulse response is therefore a useful tool to evaluate the dynamic response of any data recording system In order to measure the impulse response of your EMG instrumentation you must make either a Mode 0 or a Mode 1 recording The response of your data recording system and EMG instrumentation to each of the five leading pulses reveals the impulse response of the entire EMG instrumentation and recording system to a one millisecond 500 uV pulse Using the Whisper e 17 Common Mode Rejection Ratio The Common Mode Rejection Ratio CMRR indicates the extent to which any common mode components of a recorded signal will be rejected by a differential amplifier The differential mode component will be am
58. h the Whisper helps you interpret the results A 7 T CAMARCII EMG SIMULATOR DIF MODE COM MODE pa EMG on on Out ott ott Figure 1 The Whisper is a compact easy to use system START This manual provides complete information to enable you to connect the Whisper to your EMG instrumentation and verify that the installation was successful The standardized test signal generated by the Whisper is described together with the information that can be calculated from the signal The manual describes each of the Test Modes possible with the Whisper Recording protocols and test parameter calculation algorithms are discussed to allow you to determine the test parameter values of your EMG instrumentation After reading this manual you will be ready to use the Whisper to obtain many useful insights into the performance of your EMG instrumentation Whisper User Manual Introduction e 1 RData2 reads many common binary recording formats and generates the ASCII files required for analysis by the EMG Equipment Tester Software CE 2 e Introduction The Whisper can be connected to any mono polar or bi polar EMG system that generates either smoothed rectified EMG signals or raw EMG signals and provides a means of recording these signals to a disk file in a format that the EMG Equipment Tester software Teppista with the Whisper can read Sa aa pam 75 1024 75 1024 75_ me am 1 pm pa Figure 2 A typi
59. h the correct values when the C3D file is created using the software application supplied by your vendor The SCALE parameter and other parameters may also be directly modified using programs such as C3dEditor available from Motion Lab Systems Inc Fixed Gain Systems MA 300 EMG Systems offer individual gain settings for each EMG channel that may be preset to record specific gain levels for each EMG channel This type of system with a known gain factor for each channel or switch setting can be used to generate calibrated C3D file data very quickly All that needs to be known is the input range of the signal for a given channel gain setting in the case of an MA 300 EMG system this value can be read directly from the manual or calculated using the formula recommended by your C3D data collection system manufacturer As in calculations for variable gain systems the calibration scaling factor used for a fixed gain EMG system will be applied to the individual ANALOG SCALE parameters for the channels under investigation while leaving the universal ANALOG GEN SCALE parameter unchanged as this affects all the analog channels in the C3D file For C3D file recordings made with an MA 300 using the 3 gain setting using an ADC with a 5 volt range and a GEN_SCALE parameter value of 0 00488 the individual channel ANALOG SCALE factors should be set to the value of 0 00009083 to scale the recorded EMG test signal from the Whisper in microvolts Th
60. ifferent configurations Each of the four configurations can reveal different aspects of your EMG instrumentation Standard EMG test modes The standard EMG test signal stored within the Whisper has been chosen so that several EMG instrumentation features can be quickly tested Since both the differential and common mode components of the EMG test signal can be controlled independently it is possible to define four operation modes Dif Com Test options recording mode a length fo fon On Bi polar EMG EMG and timing parameters EMG EMG Bi polar EMG EMG and timing parameters timing parameters gt gt 22 sec gt 22 sec ee ee Mono polar EMG EMG and timing parameters Bi polar EMG Common Mode Rejection Ratio Bi Mono polar EMG Noise and offset parameters Table 2 Operation Modes and Test Features Using the Whisper e 13 It is worth noting at this point that all the Whisper tests produce results that measure not only the EMG system but also the data recording and measurement system that is used to access the EMG data The results reported from a series of Whisper tests may provide as much information about the performance of the analog EMG recording system as the EMG instrumentation that is used to acquire the EMG signal It is important that the Whisper user considers all possible error sources before evaluating the results of a series of Whisper tests Mode 0 EMG and Common Mode In mode 0 the EMG param
61. in the Spot Record Analysis screen The analysis will proceed in exactly the same manner as the Spot Record Analysis using the same five buttons to select the Whisper test files as Whisper User Manual The Whisper Mode 0 and Mode 1 test signals are appropriate when testing systems that record raw EMG signals The sample rate is determined by the number of samples recorded between the leading pulses in Mode 0 and Mode 1 test signals Whisper User Manual described above Once a Report Generator analysis has been selected and the Start Analysis button pressed an analysis will be performed and a report printed on the default Windows printer attached to your computer Interpretation of the Results The EMG Equipment Test software has been developed test the performance of an EMG recording system using a Whisper generated EMG test signal In addition it the basic test and quality assurance functions the EMG Equipment Test software can be used to compare the behavior of different EMG systems and data collection instrumentation in separate laboratory or data collection environments When you are evaluating the performance of an EMG system it is important to know what results you expect to obtain from the tests in order to determine the operational status of the equipment Since the characteristics of the Whisper generated test signals are well known it is possible to predict the results of many of the tests The characteristics of the s
62. ing and Dynamics The timing and the dynamics of the EMG instrumentation and recording system can be tested using the Whisper Mode 0 and Mode 1 EMG test signals by studying the five leading pulses in the differential EMG signal Since the shape and the time between the leading pulses is exactly known they can be used to check the e The sample rate of the EMG recording system e The dynamic response of the EMG recording system Common Mode Rejection Ratio By applying only the common mode component a Mode 2 test to an EMG instrumentation system it is possible to evaluate e The Common Mode Rejection Ratio of the EMG instrument During a Mode 2 test the common mode signal component is applied to a bipolar EMG instrument Since this signal is present at each of the differential outputs of the Whisper the EMG instrument should reject this signal a 40 Hz sine wave It is known that the amplitude of the sinusoidal signal from the Whisper equals 1 0 Volt Thus a simple measurement of the amplitude of the sinusoidal present in a Mode 2 recording enables us to measure the extent to which the Common Mode signal has been suppressed This is called the Common Mode Rejection Ratio and is important because it is the primary method by which bi polar EMG recording systems eliminate line frequency signals 50 or 60 Hz depending on your location from the EMG signal present on the subject It is worth noting that there is also a common mode component
63. ing safety check The Whisper is manufactured by Roessingh Research and Development Roessinghsbleekweg 33b 7522 AH Enschede Netherlands Phone 31 53 4875777 Fax 31 53 4340849 e mail rrd rrd nl Motion Lab Systems Inc 4326 Pine Park Drive Baton Rouge LA 70809 Phone 1 225 928 GAIT 4248 Fax 1 225 928 0261 Email support motion labs com http www motion labs com Printed in the United States of America Motion Lab Systems Inc 2000 Contents Introduction 1 Introduction The Whisper Congratulations on your purchase of the Whisper EMG equipment test package manufactured by Roessingh Research and Development and distributed in the United States by Motion Lab Systems Inc From now on you can use the Whisper to test your EMG instrumentation in an easy fast and reliable standardized manner The Whisper can be used in seconds to perform a quick functional test or can perform a specification check and comparison with previous test results A quick functional test of EMG equipment is based on the idea that a faulty EMG system and a normal system will produce different EMG records when tested with a known reproducible EMG input signal The inspection of a system s response to a standardized EMG signal is therefore a good way to verify the performance of an EMG instrument or an EMG data collection system The Whisper generates this standardized test signal for your EMG instrumentation and software included wit
64. ipment tests Whisper User Manual Installation Getting started RData2 is a powerful binary to ASCII conversion utility supplied by Motion Lab Systems Inc Whisper User Manual The best way to avoid problems during installation of the Whisper is to read this entire chapter before you start the installation The chapter lists all of the items that you should receive with the Whisper and describes the simple process of connecting the Whisper to your EMG instrumentation In order to be able to install the Whisper properly the package contains the following items e The Whisper an EMG signal generator e Four AA batteries e AnEMG signal cable with LEMO connector e A ground reference cable e The EMG Equipment Tester software e The Whisper User manual this document In addition to the Whisper equipment and software Motion Lab Systems includes a copy of the RData2 file translation software This software package can be used to generate the DST files required by the EMG Equipment Tester software supplied with the Whisper RData2 reads C3D and Dataq data files and converts them to CAMARC standard DST files The items supplied with RData2 are e RData2 Software e RData2 User Manual e Customer Registration code Please check that you have all the Whisper and RData2 items before continuing the installation Please contact Motion Lab Systems if you can not find any of the items listed Our mail address phone numbers an
65. is correct before attempting to analyze the data with the Whisper EMG Analysis Software A C3D and DST file viewer MLSviewer illustrated at the end of this chapter is available from the Motion Lab Systems Inc web site at http www motion labs com Recording the Test Signals Whisper User Manual Once you have made some initial basic tests to verify the correct connections gain levels and the recording parameters you are ready to start making some test runs or recordings The Whisper Mode 0 provides the best test signal to the initial set up of your recording or test environment This mode produces five leading pulses at intervals of one second Each pulse is a single positive going square wave with an amplitude of 500uV and a duration of one millisecond These timing pulses are used by the Whisper EMG Test Software to determine the sample rate of the system under investigation Note that the high frequency component of the rising and falling edges of the square wave timing pulse will be altered by the frequency response of the system components under test As the timing pulse contains a DC component you will not be able to measure the pulse amplitude accurately with any EMG system that incorporates a High Pass filter A Whisper Tutorial e 33 Figure 22 Whisper timing pulse 20Hz 2 000Hz bandwidth A brief switching transient The digitized Whisper EMG signal starts exactly one second after the fifth
66. king on the EXIT button in the center of the top three buttons Then you will return to the Spot Record Analysis screen Preparing a Spot Record Analysis You can perform a multi channel equipment test by selecting the Spot Record Analyzer option in the pop up menu button in the Selection window of the Spot Record Analysis screen Selecting the Spot Record Analyzer causes five buttons to appear in the Selection window The five buttons allow you to select which parameters which you want to measure and display For the tutorial please select all parameters by clicking on each button As you select the buttons you will see the appropriate filename dialog boxes appear in the File Information window Note that when you have selected all five parameters there will be three separate file name dialog boxes displayed These are EMG file Common Mode file and Noise Offset file You can either type the filename and path into each dialog box directly or use the browse feature to point and click on the appropriate filename The EMG file is the file that contains the Mode 0 Mode 1 EMG test recording from the Whisper A Mode 0 or Mode 1 recording provides information on EMG frequency and amplitude data properties as well as timing and dynamic information As a result selecting any one or more of the first three buttons will display a single filename dialog request for the EMG file By convention the EMG filename will the file open window To display the
67. l of a system performance test comparison to detect any degradation malfunction or change in the EMG system and recording instrumentation in order detect these problems at an early stage Therefore a system performance test will compare the results of a recent EMG system test to the results of an earlier test In this way invalid EMG measurements can be avoided and appropriate maintenance actions can be undertaken The starting point of a systems performance test are the results from an earlier recorded test of the EMG instrumentation The saved results can be compared to the results of a new equipment test If you perform a full EMG system performance test on a regular basis for example once a week you should find that the week to week Using the Whisper e 19 It is recommended that the Whisper tests be run on a regular basis in order to maintain a history of the performance of your EMG instrumentation 20 e Using the Whisper changes of the test parameter values are very small lt 1 0 indicating the EMG instrumentation and data collection system are working properly Any large deviation in the test parameter values will suggest that the performance of your EMG instrumentation has changed in some way It is almost impossible to make any general statements here about the values of specific deviations in parameter values since they depend a lot on the type of instrumentation and the environment in which you execute your measuremen
68. ld know that e The header consists of a file header line first line starts with text section header lines which indicate the beginning of a text section these lines begin with and are followed by text lines and data section header lines which indicate the beginning of a data section these lines begin with and will be followed by data lines e The file header line contains information about the CAMARC II lexicon and about the date and the place of the experiment e The text section header lines and the text lines contain comments on the experiment The contents of text section header lines may not be changed and is case sensitive The contents of the text lines needs to be edited in order to fit your test data e The data section header lines indicate parameters The value of these parameters can be found in the data line following the data section header line The contents of data section header lines may not be changed and is case sensitive The contents of the data lines needs to be edited in order to fit your test data Whisper User Manual e The lines in the header are separated by EndOfLine characters EOL CR Carriage Return LF Line Feed ASCII 13 ASCII 10 e The order of the file header line the text section header lines and the data section header lines as shown above is the prescribed order If you change this order your EMG Equipment Tester software may not be able to analyze your Test date automatical
69. ly In order to avoid problems with the EMG Equipment Tester software it is recommended that you only change the following information in the header of a Test date file e The name of the city and the date of the experiment in the file header line Be sure that you have written the date in the appropriate format and that you separate the date and place by only 1 SPACE ASCII 32 e The text in text lines following the text section header lines You may include any comment over as many lines as you want in order to describe the experiment as clear as possible Be sure that you use the appropriate EndOfLine characters e The sample frequency of your recording system in the line following AdcSampleRate Replace 1024 by the sample rate in Hz of your recording system e The resolution in bits of your recorded data in the line following AdcRESolution Replace 2 by the resolution in bits of your recording system e The number of EMG channels of which your test data file contains the recorded data Replace 4 in the line EMG 4 by the number of EMG channels in your Test date file maximum number of channels 4 The header is followed by the actual test data The test data should be written as follows e Each column contains the data of 1 separate EMG channel TABs ASCII 9 separate the columns e Each row contains 1 sample value of each recorded EMG channel Each line ends with an EOL character ASCII 13 ASCII 10 e The da
70. n window Only files that have names in the format name In order to demonstrate a full Spot Record Analysis 3 demonstration files have been provided on the data diskette that comes with your Whisper These are 951001e1 DST 951001c1 DST and 95100In1 DST These 3 files contain EMG data Common Mode data and Noise Offset data measured with bipolar raw EMG instrumentation Select all five test parameter options and select the three demonstration files As soon as all three filenames are loaded the software will display the Start Analysis button in the Control window Click on this button in order to start the Spot Record Analyzer Whisper User Manual The EMG Test software e 49 Use the Spot Record Analyzer to view the data analysis results and the Report Generator to send copies of the analysis results to the current default printer 50 e The EMG Test software The Spot Record Analyzer screen As soon as the Spot Record Analyzer is started the screen which is shown in Figure 35 should pop up and will be initialized The screen is divided into five windows the EMG parameter window the Common Mode parameter window the Noise Offset parameter window the File Information window and a message controller window The first three windows will show the results of the data analysis Each column relates to one separate EMG channel and each window is related to one of the files which has been selected in the Spot Record Analysis screen Th
71. nd EMG recording channels for any signs of degradation A faulty EMG system will produce a different EMG record from a functioning EMG system when both systems are presented with a standard EMG test signal such as generated by the Whisper The standardized test signal is stored in EPROM s inside the Whisper Each Whisper contains an identical set of EPROM s and thus every Whisper generates an identical EMG signal for each test The signal consists of two components these are e 6A differential mode component e A common mode component The differential component consists of five positive leading pulses that are followed by a digitized EMG signal The common mode component consists of a 40 Hz sine wave Each of the two components can be generated and applied to the EMG output signal independently via the two DIF and COM mode switches on the front of the Whisper Both signals are generated as soon as the START button is pushed and released to allow the Whisper to produce a range of test signals under control of the user The ability to combine and separate the differential and common mode components of the EMG test signal is invaluable in fault finding and testing EMG systems and components The Test Signal e 9 The standard test signal The standard Whisper test signal consists of a differential mode signal with a common mode component superimposed on the signal This allows a number of different EMG instrumentation parameters to be o
72. nel will require the correct fixed calibration values for each channel An MA 300 system with a gain switch setting of 3 a gain of x5714 and connected to a 5 volt ADC will require a Fixed Calibration value of 0 000875 Volts which can be entered as shown in A Whisper Tutorial e 29 Full details of the public C3D file format description together with common parameter information is available from the C3D web site at www c3d org 30 e A Whisper Tutorial C3D Recordings This section will discuss the gain calibration of sample recordings made with the MA 100 and MA 300 EMG systems using a commercial motion capture system with a proprietary ADC card For the purposes of this tutorial the two EMG systems differ in their treatment of the EMG signal as the MA 100 system has a continuously variable signal gain while the MA 300 system offers discrete switched gain levels This section assumes that the reader is familiar with the stand alone calibration protocols described in the preceding pages and as a result descriptions of the individual features of the example EMG systems will not be repeated C3D files are a common biomechanics standard that allows analog and 3D data to be recorded in data files together with various parameters that describe the data A standard analog channel consists of a number of analog samples together with two gain factors that are applied to the analog signal to transform the binary samples into real worl
73. no foo mioo Table 4 Test parameter values of the standard test signal The sample rate at which the EMG test signals will be recorded is set by the data sampling system that is used to record EMG signals The sample rate reported by the Spot Record Analyzer must match the value that has been set for the data sampling system regardless of the type of EMG system raw or smoothed rectified EMG recordings The EMG Test software e 53 The Spot Check and Report Generator options function in the same way except the Report Generator will create a printed copy of the analysis results on the default Windows printer 54 e The EMG Test software The filter response Common Mode Rejection Rate CMRR and the Noise and Offset of the EMG system depend a lot of the quality and type raw EMG or smoothed rectified EMG of the EMG system under test This makes it difficult to suggest an ideal set of numbers for the Spot Record Analyzer to report The shape of the dynamic filter response depends on the type of EMG system raw and smoothed rectified EMG systems will produce radically different displays due to the pre processing inherent in a smoothed rectified EMG system The CMRR should be as high as possible usual between 80 to 120 dB The Noise and Offset of the EMG instrument under test should be as low as possible a few microvolts Figure 37 shows the results of a multi channel Equipment Test of an EMG recording instrument tha
74. not push the Start Button before you started your EMG recording instrument If you only view your EMG recording this won t be a problem If in a later stage you are going to use the EMG Equipment Tester software the spike will cause problems if its amplitude exceeds the amplitude of the leading pulses Your recording contains less then the five leading pulses The sample rate of your recording device is low compared to the impulse response of your EMG instrumentation Increase the sample rate of your recording device Check to see if you started the Whisper prior to starting recording Some recording systems may take a second or so after the commond to start before they actually record any data When you start the EMG Equipment Tester software a window pops containing the message Could not allocate the total amount of memory requested 20480000 bytes Continuing with bytes Appendix A2 e 67 e This message indicates that you have less than 20 Mb of RAM memory available this may not cause too much of a problem unless you have less than 16 Mb The EMG Equipment Tester software may run into serious memory problems if there is not enough memory to perform the software analysis functions While processing data an error message appears Application memory full Saving and closing other applications for instance a mail program running in the background can free memory You may need to increase the Total Memory allocated to LabVIEW
75. nstrumentation The Whisper is working and has been installed correctly if an EMG recording from a known working EMG systems is comparable to the EMG signals illustrated in either Figure 9 jor Please consult the troubleshooting guide in Appendix A2 ht the end of this manual if you do not see these signals Installation e 7 8 e Installation Whisper User Manual The Test Signal A Functional description Whisper User Manual Roessingh Research and Development have developed the Whisper as a tool for quality assurance and routine checking of the performance of EMG instrumentation in a biomechanics laboratory Its primary goal is to detect degradation in the performance or malfunctioning of the equipment in order to alert the users to any problems with their system at an early stage Information generated by the Whisper allows the laboratory engineers and technicians to schedule regular maintenance to avoid making invalid EMG measurements and or recordings The basic idea of an equipment test is that a standardized EMG test signal will be applied to the EMG instrumentation on a regular basis The output of the EMG instrumentation will be recorded and test parameter values will be calculated from the recorded signal in order to obtain a record of the performance of the EMG instrumentation and recording system By comparing the test results from a Whisper test with the results of earlier tests it is possible to check that the EMG system a
76. nt Tester software If you have calculated the CMRR you need to verify that the estimated frequency of the Common Mode signal is indeed 40 Hz before you can be sure that the CMRR calculation is a reliable measurement Whisper User Manual Noise and Offset Test Protocol Mode 3 The test protocol for Noise and offset testing can be used to test the Noise and Offset of the EMG instrument under test e Connect the Whisper to your EMG instrumentation e Prepare your recording system to record the standard test signal with out saturating during at least 10 seconds e Set both the COM and DIF switches off e Switch the Whisper on e Start your recording device after pushing the Start Button Write the data that you have recorded in the appropriate DST data format and name the file as follows YYMMDDmN DST e Run the EMG Equipment Tester software and select the noise and offset analysis If you use the protocol in this manner the total amount of Noise Offset that you will find indicates the Noise Offset of both your EMG recording instrument and the Whisper This amount of Noise Offset is superimposed on all your test data A full Equipment Test When making connections to the Whisper take special care to avoid introducing any AC noise into your EMG system under test Whisper User Manual A full Equipment Test yields that all facilities of the EMG Equipment Tester software will be used simultaneously such that a single analysis
77. ntation in separate laboratories to check that their data collections systems and EMG equipment is comparable It is important that the data recorded from the Whisper is maintained according to a standard protocol if the Whisper will be used for equipment testing The signal data protocols have been discussed earlier in sing the Whisper bn page loff this manual however the storage of the information needs to be defined to some extent if the EMG Equipment Tester software will be used to analyze the recordings This chapter will therefore discuss the protocols that must be followed in order to use the EMG Equipment Tester software These are e The data format the EMG Equipment Tester software can read and analyze e The three basic Whisper data modes Mode 0 1 Mode 2 and Mode 3 signals This chapter will end with a description of a full equipment test and some recommendations for proper use of the EMG Equipment Tester software The CAMARC DST format The following description of the Whisper file formats is provided for the benefit of anyone who is unable to generate native DST file by either directly exporting them from their data collection software or by using the Motion Lab Systems program RData2 that is supplied with the Whisper The Rdata2 program can generate Whisper compatible DST files from any C3D or Dataq EMG data file in seconds File Descriptions e 57 Full details of the CAMARC DST file formats may be found in the files
78. nterpulse time is the time between 2 successive leading pulses e Common Mode Amplitude is the amplitude of the sine wave e Common Mode Frequency is the frequency of the sine wave The Test Signal e 11 12 e The Test Signal Whisper User Manual Using the Whisper Standardized EMG testing Whisper User Manual The Whisper has been developed to provide a well defined reproducible test signal for standardized EMG equipment testing Standardized testing can be performed in a number of separate steps First the EMG test signal from the Whisper is applied to the input of the EMG instrumentation under test The output of the Whisper is then recorded through the EMG instrumentation The recording is then evaluated and parameters calculated from the recorded data Finally the calculated values can be either compared to the known input values or compared with the results of prior tests in order to be able to draw conclusions about the performance of the EMG recording system and EMG instrument under test In order to be able to draw reliable conclusions about the performance of the EMG instrumentation it is important that each of these steps is performed in exactly the same standardized way each time the equipment is tested This chapter will discuss how all this can be achieved Since the differential mode and common mode component of the Whisper EMG test signal can be selected independently the standard test signal can take any one of four d
79. o 200uV RMS at the EMG pre amplifier inputs This calibration source can be used to calculate the system gain after the variable gain control has been adjusted to produce a suitable EMG test signal as discussed earlier Once the variable gain controls have been set to the desired position they must not be moved or adjusted unless you are prepared to repeat the gain calibration procedure The calibration procedure is simple A calibration recording is made once the individual gains have been set The MA 100 uses its internal calibration source when the CAL button is pressed applies a known calibration source to each EMG input Since we know the input signal 200uV RMS sine wave and can directly measure the recorded level of the resulting output signal we can easily calibrate the system to record data scaled in uV or directly calculate the system gain n7 WINDAQ MA100CAL WDQ el Ea File Edit View Search Scaling Transform XY Options Help 1 5759 Volt off SEC TM off EOF E gt si Figure 17 A calibration level recording using a 200uV RMS input A Whisper Tutorial e 27 It is vital that you do not calibrate a measured peak value with an RMS value 28 e A Whisper Tutorial The calibration recording shown in Figure 17 using the Dataq Browser software that is supplied free of charge with the Dataq ADC cards It shows the recorded signal from an MA 100 calibration signal at this point the ADC system is
80. of the 1 file and YOURSIM RES as the name of the 2 result file As soon as both filenames have been loaded the Start Analysis button will be displayed in the Control window Click on the Start Analysis button to start the Spot Check or the Report Generator and the screen shown in Figure 37 will appear Note that if the file selection procedure is not completed properly the error message lt Not A Path gt will appear in the File dialog box Repeat the file selection procedure until both files have been selected yoursimres 09 28 95 Figure 37 Spot Check screen of the EMG Equipment tester The Spot Record screen displays the results of two prior Spot Record Analysis operations Each Spot Record Analysis results file can contain details from one to four EMG channel analysis tests The left side of the window displays the contents of the first results file each column displayed in this half of the screen contains the test results of one EMG channel At the right of the screen you will find the contents of the second results file Again each column contains the test results of a separate EMG channel The Spot Record screen provides an easy way to compare two result files If an equipment test has been done according to a standardized measurement protocol the contents of two different results files relates to the same EMG channels of the instrument under test In that way the performance of the EMG instrument under test can be tested
81. of the system gain of the EMG system being tested is easily estimated by dividing the maximum output voltage of the system by the maximum input voltage for a given gain setting in this case 10 Volts divided by 0 00175 Volts or 5 714 however in this case various component tolerances are known to reduce the gain for this setting to a figure of 5508 The ADCrange is considered to be 20 Volts in this instance although the actual range of the ADC card is quoted at 5 volts This is due to an ADCgain factor of x2 that is applied within the ADC card This has the effect of amplifying the incoming signal to effectively reduce the ADC input voltage range to 10 volts 5 Volts to 5 Volts which accounts for the manufacturers quoted range of 5 volts The ADC card has 12 bits of sampling resolution resulting in a total resolution of 4096 GEN_SCALE is a usually fixed universal scaling factor in the C3D file and usually has a value of 0 00488 or 1 00 although other values are acceptable It is important that the SCALE value is calculated and entered correctly as this determines the scaling of the EMG signals that are recorded in the C3D file although it does not otherwise affect the quality of the signal Incorrect scaling of the test signals from the Whisper is a common problem when users first start to examine the EMG signals It is recommended that anyone using the C3D file format should carefully examine the data scaling and verify that it
82. on is symmetrical Even the smallest common mode asymmetry at the input of your EMG instrument can cause your EMG instrument to saturate Check that your EMG instrumentation has been set correctly If the EMG system appears to work in Mode 1 but not Mode 0 then you may have a very poor CMRR perform a Mode 2 test to determine your systems CMRR response The recording contains line frequency signals There is a lot of common mode interference Check all the connections between the Whisper your EMG instrumentation and the laboratory ground If you are running a Mode 0 test then check that your EMG inputs are actually differential inputs If the system appears to work with a Mode 1 test but fails a Mode 0 test then it is likely that your EMG system is either not a differential input system or does not have a good CMRR The recording is very noisy Check all the connection between the Whisper your EMG instrumentation and ground Verify that the Whisper and or your recording instrumentation have not been placed near to noise sources such as computer screens or equipment which generates electrical or magnetic fields Your recording contains more than five leading pulses If you see a spike 1 2 second after the Sth leading pulse this is due to an internal switch in the Whisper This spike will not cause any problems If you see a spike at the beginning of your EMG recording this is due to pushing the start button You probably did
83. ou to the Windows operating system 46 e The EMG Test software This chapter is a tutorial in the use of the EMG Equipment Tester software that uses a number of sample data files that are provided as part of the software installation This tutorial starts from the main screen of the EMG Equipment Tester shown in This screen contains three windows the Selection window the File Information window and the Control window While using the EMG Equipment Tester software you can expect buttons and selection switches to pop up in the Selection window These buttons and switches allow you to select the task and data analysis operations that you want the software to perform Depending on the analysis or operation requested the EMG Equipment Tester will prompt the user for the data files needed to complete the operation These requests will appear in the File Information window The analysis operation can not start until the appropriate information is supplied Buttons in the Control window allow you to start the analysis or move to a different application option The next two sections discuss the basics to perform the Spot Record Analysis and Spot Check options which are entered by clicking on the corresponding button in the Control window The Spot Record Analysis screen Click on the Spot Record Analysis button in the Control window of the Main Screen to enter the Spot Record Analysis you should see the screen shown in The Exit to Main button
84. ple rate Whisper User Manual Whisper User Manual Since we know that the EMG signal starts exactly one second after the last leading pulse and that the EMG signal is 15 seconds long it is easy to extract the EMG signal data from the EMG file and calculate the RMS and Mean values Frequency parameters e The Median frequency Fineq of the Power Spectrum of the recorded EMG signal in Hz e The Mode frequency F mode of the smoothed Power Spectrum of the recorded EMG signal in Hz e The 3 dB points of Frode F 34 lefts F 34B right Of the smoothed Power Spectrum of the recorded EMG signal in Hz These parameters are calculated from the first two seconds of the EMG signal in the EMG file The two seconds are extracted from the EMG file using the same algorithm as the amplitude parameters discussed above The Power Spectrum is calculated and by integrating the Power Spectrum the total power is calculated The median frequency can be determined by integrating the Power Spectrum until the frequency at which the integrated power equals half of the total power This median frequency F nea thus cuts the Power Spectrum in two pieces of equal power Frode 18 the frequency in the smoothed Power Spectrum at which the spectrum is maximal Smoothing yields multiplication of the Power Spectrum with a Papoulis window The F_34g points are related to Finoge Two points can be separated F_34g jeg and F_348 right They can be defined a
85. plified by the EMG instrumentation measuring chain and can be used to calculate the overall system gain The Common Mode Rejection Ratio can therefore be determined by dividing the amplitude of the Whisper s common mode sine wave 40 Hz amplitude 1 0 Volt by the amplitude of the sine wave recorded in a Whisper Mode 2 recording The Common Mode Rejection Ratio of your EMG instrument is the 20 log value of this ratio In general most EMG systems should have a Common Mode Rejection Ratio of greater than 80 dB The Whisper generates a test signal for Common Mode Rejection Ratio calculation in Mode 2 The first five seconds of a Mode 2 signal consists of a quiet baseline followed by a low level sine wave The amplitude of this sine wave will depend on the ability of your EMG amplifier to reject Common Mode signals Noise and offset parameters A Whisper Mode 3 recording enables you to measure the noise and DC offset parameters of your EMG instrumentation In this mode the output of the output of the Whisper is 0 0 volts and contains only the internal noise that is inherent in any signal system By measuring the RMS and Mean values of the recorded EMG signal in Mode 3 it is possible to calculate the amount of noise and the offset of the EMG instrumentation and data recording system While the internal noise generated by the Whisper is very small it is not zero This is possible to measure the internal noise of the Whisper by comparing the results of a
86. pment Tester software If the EMG Equipment Tester software has been installed correctly it can be run by double clicking on the EMG Tester icon on the desktop or by running it from the Start menu applications group that you specified when the program was installed This is normally the Gait Lab group About the EMG Equipment Tester The EMG Equipment Tester Version 1 2 Copyright c 1997 Roessingh Research and Development b v This product is licenced to Motion Lab Systems Baton Rouge LA USA Product ID RADSEET 9510 04 _coninue Labview r executable Copyright c 1994 National Instruments Corporation All rights Reserved United States Patent Nos 4 901 221 4 914 568 other patents pending Figure 30 The software splash screen showing the licensing information Whisper User Manual The EMG Test software e 45 When the application first starts it will display a splash screen that displays some information about the software such as the registration number and site location This screen will disappear after twenty seconds or as soon as the Continue button is pressed The EMG Equipment Tester software will then display the main screen as shown in You are now ready to analyze test recordings that have been collected using the Whisper Using the EMG Equipment Tester software You can exit the EMG Equipment Tester by clicking on the Quit button in the main menu The software will then return y
87. q WDQ files it is essential that all required scaling factors have been applied to the raw EMG data file before RData2 is used to export the Whisper DST file If you find that you have to change an EMG channel scaling factor then this must be done in the original data file and the data exported again to overwrite the older DST file Whisper User Manual ANA files collected with a Motion Analysis Corporation system require that a specific gain factor is entered into RData2 before generating a Whisper DST file Whisper User Manual Using RData2 with ANA files EMG data files generated using a Motion Analysis Corporation system must be in the ANA compressed ASCII format in order to be read by RData2 This file format does not have any provision for scaling the individual data channels and so the scaling factor must be determined and entered in the RData2 MAC format options tab In general data collected on a Motion Analysis Corporation system in the ANA format uses a fixed gain range normally this is 5 Volts although gains corresponding to 10V 5V 2 5V and 1 25V can be used RData2 Options ADC Selection ADC Parameters DST Export TextExport C3D Selection VAD Selection MAC Selection CODAS Selection BTS Selection p Header Yes Analog Data Yes Scale factor for Whisper Output 0 000100 ANALOG Yes Figure 26 The MAC selection tab includes a specific scale factor
88. r to that illustrated in This problem can also be caused by an incorrect choice of data acquisition input levels where the ADC card range is much greater than the output level of the EMG system Figure 16 Too little gain causes the signal to be lost in the background noise If you are working with an EMG system that does not have adjustable gain controls then it is likely that you will either see a signal that is the correct level or you will see a signal that appears to be too low While it is possible to use the Whisper and obtain accurate results with a low EMG test signal this is not an optimal configuration for either testing or regular use One of the principal test performed by the Whisper is to report the EMG recording channel gain This test requires that the recording levels are correctly set for the entire EMG signal recording chain In other words we expect that an input signal of one millivolt will be reported as a signal level of one millivolt This would be a simple task except that most EMG systems produce an output level that is set at a convenient level for computers to record Both the MA 100 and MA 300 EMG systems used in this tutorial produce output signals in the range of 5 Volts so this signal must be scaled to accurately represent the original input level This tutorial will discuss the methods used to calculate this scaling factor for each of the two EMG systems MA 100 and MA 300 in two dif
89. re is reflected in the diagram shown below ie e Spot Record Analysis Spot Check level 1 i Spot Record Report Report level 2 Quickview Analyzer Generator Spot Check Generator Table 3 Function Diagram of the EMG Equipment Tester software From the main menu you can choose to do a Spot Record Analysis or to do a Spot Check Within a Spot Record Analysis you are able to e View the data files recorded using the Whisper Quickview e Make a Spot Record of a data file which has been recorded using the Whisper You can extract a number of EMG parameters from the data and store these parameters into a file for further investigation Spot Record Analyzer Whisper User Manual e Print the results of a Spot Record to the default Windows printer Report Generator Spot Record Analysis will analyze data from up to four different EMG channels at one time for multi channel equipment tests Within a Spot Check you are able to e Compare two Spot Records with each other in order to check the performance of your EMG instrumentation Spot Check e Print the results of this Spot Check to the printer Report Generator The Spot Check allows you to analyze data that provides detailed information about your system performance and specifications Data from independent tests made over a period of time can be compared to verify continued system performance Figure 29 The main screen of the EMG Equi
90. re will directly indicate the range of recorded signal for the channel in uV at the skin surface or pre amplified electrode input in the case of the illustration in this range is 897 5uV Whisper User Manual It is important to note that the actual calibration of the EMG system for data collection is performed when the range values are entering in the Dataq Analog Data Acquisition software Whisper User Manual This value can be entered into the Dataq Data Acquisition software as a pair of Fixed Calibration values Function F12 or accessible via the Edit menu to allow the Dataq Acquisition system to create output data files that contain test data that is scaled directly in microvolts uV as required by the Whisper EMG test software Dataq files that are recorded in microvolts can be quickly converted by RData2 to create the DST files required for analysis and reporting Fixed gain systems Fixed gain EMG systems may offer no user gain adjustment or may offer a limited number of preset gains The gains may be chosen as a single value that applied to all the EMG channels or may be individually preset for each EMG channel MA 300 EMG Systems offers a range of individual gain settings for each EMG channel these may either be preset to record a fixed level or preset to individual levels that are considered optimal for the EMG source under investigation This allows the user a great deal of flexibility in selecting an optimal
91. ronments The following chapters explain how to use the EMG Equipment Tester software and assumes that you have read the earlier chapters explaining the Whisper EMG signal generator If you have not done so please read the earlier chapters that explain the Whisper functionality and operating modes as this information will not be repeated here The EMG Equipment Tester software reads EMG data that has been stored in files using the DST file format defined by CAMARC If your data collection system does not produce EMG data files that can be stored in the DST format then you may need to use the accompanying RData2 software package This creates DST files in the correct format from C3D files and WDQ files created by Dataq data acquisition software programs CODAS and WinDag Pro Software installation The EMG Equipment Tester software has been developed under LabVIEW and runs under the Microsoft Windows 95 Windows 98 and Windows NT operating systems Before installing and using the EMG Equipment Tester software you therefore need to understand the basic skills for working with your version of the Microsoft Windows operating system The typical requirements for an IBM compatible PC to run this software are e At least a 100MHz Pentium processor with a minimum of 32 Mb of main RAM memory and 10 Mb of free disk space the software may be installed on a network drive The EMG Test software e 43 Add Remove Programs 44 e The EMG Test so
92. s follows for any frequency below Fap jen and above F_z4g right the value in the Power Spectrum will never exceed Frode 2 The frequency bands outside the F_34g points therefore indicate frequency ranges in which the power will never increase half of the maximum Power F mode 2 The frequency band between the 3dB points can therefore be regarded as a measure of the bandwidth of the spectrum Dynamic properties e The sample rate of the EMG instrument under test in Hz e The dynamic response of the EMG instrument under test in microvolts The sample rate of the EMG instrument under test is calculated from the leading pulses in the EMG record as mentioned above The dynamic response that is shown in the Spot Record Analyzer screen after an analysis is the response of the EMG instrument to the first leading pulse in a Mode 0 or Mode recording The graphs that are plotted show the shape of the filter responses start 10 samples before the pulse arrives and show the response of the system as long as the absolute value of the amplitude is more then 1 of its maximum value It is important to note that the leading pulses are only 1mS wide as a result they may not always be accurately recorded if the frequency response of the EMG instrumentation does not extend to the higher frequencies or the analog data collection sample rate is low The EMG Test software e 51 52 e The EMG Test software Common Mode parameters e The Common Mode
93. sample data supplied with the EMG Equipment Tester software you should select the file name 951001E1 DST that is provided with the installation Whisper User Manual __ B PAEMGEQTST data 951001e1 dst __ 3 PAEMGEQTST data 951001c1 dst J 3 PAEMGEOTSTAdata S51001n1 dst _ Dynamical Properties _ Common Mode Rejection Ratio _ Noise and Offset Parameters Figure 34 Spot Record Analysis window when preparing a Spot Record Analysis The Common Mode file is the file that contains the Mode 2 Whisper recording This file is generated when the Whisper is used to apply a common mode test signal to the EMG instrumentation This test enables the Common Mode Rejection Ratio CMRR to be measured The dialog box requesting the Common Mode File will appear as soon the Common Mode Rejection Ratio button is selected in the Selection window You should enter a filename in the Common Mode file dialog box by convention only those files window A file can be selected by double clicking on its name for the purposes of this tutorial select the file 951001C1 DST that can be found in the data directory that is created when the application is installed The Noise Offset file is the file that contains a Mode 3 recording This recording is used to measure the noise and DC offset levels the EMG instrumentation The dialog box for this filename will appear as soon as you select the Noise and Offset Parameters option in the Selectio
94. sper tests contain a lot of information about the performance of the EMG instrumentation under test In this section we will explain how the various results can be evaluated Sample Rate The sample rate of the recording device can be determined by counting the average number of samples between any two consecutive leading pulses produced at the start of a Mode 0 or Mode 1 recording Since the five leading pulses repeat at a fixed rate the average of the number of EMG data samples between the five pulses must equal the sample rate of the recording device The measured sample rate of a Whisper test should equal the sample rate of your EMG data collection system 16 e Using the Whisper Whisper User Manual You must obey the Nyquist sampling theorem when recording data from the Whisper to test the impulse response of any system Whisper User Manual Amplitude parameters Since the Whisper generates exactly the same EMG test signal during every Mode 1 and Mode 2 test you can easily measure the gain and any DC offset in your EMG instrumentation and data collection system The RMS and the Mean values of the input EMG signal are known these are 200 uV RMS with a Mean of 0 uV By measuring these values from the recorded EMG data after it has passed through the EMG instrumentation and data recording system you can learn a great deal about the performance of the entire EMG instrumentation and recording system In order to measure the EMG
95. t records bipolar raw EMG sample rate 1024 Hz If you compare these results with Fable 4 you should be able to conclude that the EMG instrument is functional and behaving as expected Spot Check The Spot Check option allows you to run system performance specification and comparison tests You can enter the Spot Check option by clicking on the Spot Check button in the Control window of the Main menu screen The Spot Check option will display a selection button in the Selection Window this has two selections which are Spot Check and Report Generator Spot Check will display the results on the screen while Report Generator will also send the results to the default Windows printer The File Information window displays two file selection dialog boxes these expect you to enter the names of two result files res A new result file is created by the Spot Record Analyzer see page 50 whenever a Spot Analysis is performed and contains a record of the analysis results Spot Check Figure 36 The Spot Check option Executing a Spot Check is very easy first select either the Spot Check or Report Generator option from the pop up menu in the Selection window Then switch to the File Information window then and load the name of the 1 Results file A pair of sample results file are provided with the EMG Equipment Tester software these are Whisper User Manual the files 95 00101 RES and YOURSIM RES Load 95100101 RES as the name
96. ta loads The display will show the first second of each data recording on the screen The Y values of all graphs are in the same range The minimum and maximum values of this range are shown The initial view of the sample file will display four flat lines as the start of each channel of the sample recording containing the five timing pulses that occur in each Mode 0 or Mode 1 Whisper signal Quickview allows you to scroll quickly through your recordings It can be used to get a quick overall view of the data quality and allows the user to check that the recorded EMG signals are appropriate to be used in the Spot Record Analyzer It has an easy to use interface containing only three buttons By clicking on the lt lt lt or the gt gt gt button the graphs will scroll to the left or the right The EMG Test software e 47 The EMG Equipment Tester software will only open files with the correct filename format e g nnnnnnEn DST 48 e The EMG Test software If you scroll through the sample recording by continuously clicking on the gt gt gt button you will easily see that the standard Whisper test signal has been recorded correctly The start of the recording will display the timing pulses one second apart quickly followed by the digitized EMG signal Note that the signal has been recorded at very similar levels in each channel Quickview Figure 33 Quickview screen of the EMG Equipment Tester You can leave Quickview by clic
97. ta should be written as text integers the file is an ASCII text file Each test integer should indicate the measured value in microvolt e At the end of the test data an EndOfFile marker EOF ctrl z should be included If you have written a test data file in the appropriate format you can save the file to disk This file should have a name according to the following format YYMMDDItN DST in which e YY stands for Year 95 for 1995 00 for 2000 e MM stands for Month 01 for January 12 for December e DD stands for Date 01 31 e t indicates the type of the test date file e for EMG file c for Common Mode file n for Noise Offset file e N stands for the files serial number 0 9 Whisper User Manual File Descriptions e 59 60 e File Descriptions EMG Test Protocol Mode 0 Mode 1 The amplitude parameters the frequency parameters and the dynamic properties of your EMG instrument can be tested as follows e Connect the Whisper to your EMG system e Setup your EMG recording instrumentation such that it can record the standard test signal without saturating during at least 22 seconds e Select the test mode mode 0 mode 1 and set the signal switches DIF and COM on the Whisper in the appropriate positions e Switch the Whisper on e Push the Whisper Start Button start your EMG data recording instrumentation and release the Start Button within one second Write the data that you have recorded in the
98. tandard EMG test signals generated by the Whisper are covered in extensive detail in sing the Whisper f this manual Using the Whisper to generate Mode 0 or Mode 1 test signals applied a signal to the equipment under test that has well known amplitude and frequency parameters of the EMG signal These values are shown in If the EMG instrumentation under test records raw EMG then the system should record the standard Whisper Mode 0 and Mode 1 test signals without significantly changing the signal properties If you run a series of Whisper tests and find that the results reported from a Spot Record Analysis shows values comparable with those of Table 4khen you can reasonably conclude that your EMG data collection and recording system is functioning correctly However if your EMG instrumentation generates smoothed rectified EMG then you will find that a Spot Record Analysis reports different numbers In the ideal case the RMS value of the recorded EMG has to be compensated with a factor 2 7 and the average RMS value should be equal to 159 68 microvolts The Common Mode frequency has to be equal to the frequency that is shown in It is also difficult to predict the values of F mea Fmode and F 343 since they depend too much on the bandwidth properties of your smoothed rectified EMG system In practice the Freq Frode and F343 parameters are not very useful if the recording instrument produces smoothed rectified EMG test parameter vae ont reme
99. to read the system output levels directly The exact method for setting these values will depend on the motion capture system that is used to collect the data questions about controlling and viewing these parameters via your system software must be addressed to your data collection system manufacturer However independent software is available from Motion Lab Systems Inc that displays the values of the parameters and data within any C3D file MLSviewer and allows the user to edit any parameter or other component of a C3D file C3dEditor The C3D file displayed in Figure 21 contains a calibration signal recorded by an MA 100 system the C3D file has a GEN_SCALE parameter value of 1 00 and an analog SCALE value of 00488 to produce an analog display that can be read directly in Volts The scale illustrates that the peak calibration signal is 2 23 Volts MlsViewer xxxcal c3d of x cA File Edit View Window Help lax x a 4 x Open Close Print Preview Print Copy About Help E Header Information X Events POINT H ANALOG FORCE_PLATFORM 2G Analog Data id LESW i RFSW 4 EMGT 4 EMG2 For Help press F1 Figure 21 Viewing an EMG calibration signal in a C3D file Since we know that the calibration signal is 282 88uV peak 200uV RMS we can calculate the correct value for the ANALOG SCALE parameter for this channel usin
100. to the standard bi polar EMG test signal Mode 0 and that any EMG instrument that performs poorly with a Mode 2 test will probably need to be evaluated with Mode 1 EMG test signals instead of Mode 0 test signals Noise and Offset It is possible to test e The noise and any DC offset in the EMG instrumentation This is done by applying neither a common mode nor a differential mode signal to the input of the EMG instrument Mode 3 Although it seems unusual to use the Whisper for this it is very useful since the input of your EMG instrumentation will be forced to 0 0 Volt ground if you switch off both signals The signal from the Whisper will however still contain the same noise and frequency components that may be present during the other EMG tests Thus by recording the null output signal from the Whisper you can measure any noise or other electrical disturbances which are present in your EMG measuring and recording chain and are superimposed on your EMG recordings You can evaluate the noise contribution of the Whisper by comparing two Mode 3 tests one test sessions being recorded with power applied to the Whisper and the second test session with the Whisper turned off Using the Whisper e 15 Protocols for standardized testing A standardized measurement protocol is of major importance for reproducible equipment testing It is therefore recommended to use the following protocol every time you execute an equipment test 1
101. ts etc When any potential problem is observed the test data produced by the Whisper is invaluable in assisting the biomedical engineer in determining the cause of the problem The system specifications test The system specifications test is similar to the system performance test but instead of comparing the test result of an equipment test with results from earlier recordings made in your own laboratory you compare your test results with results provided by the EMG instrumentation manufacturer If you obtain a set of Whisper tests that have been recorded by the EMG system manufacturer then you can use these to confirm that the EMG system conforms to the specifications Such a recording can be used as a standard for verification of the specifications of your EMG instrumentation This is especially useful when an EMG system is first installed in a laboratory since this allows you to verify that the EMG instrumentation has been installed properly and is functional The system comparability test The system comparability test allows users in separate laboratories with different EMG systems and data collection instrumentation to verify the performance of their systems and determine if the instrumentation in both laboratories is functionally similar enough to allow exchange of EMG records This test is based on the concept that the separate laboratories apply the same standardized test signal to their equipment calculate the same test parameters
102. under investigation and the response of each channel to the standardized EMG test signal is recorded simultaneously You can make a quick assessment of the EMG channel quality by looking at these recordings If the recordings are in phase and the amplitude of the individual signals is similar then it s likely that the performance of the EMG channels will be acceptable A full multi channel equipment test consists of a number of recordings For a bipolar EMG instrument it is necessary to make three recordings a Mode 0 recording to test the timing properties and the dynamic properties of each channel a Mode 2 recording to test the Common Mode Rejection Ratio of each channel and a Mode 3 recording for noise and offset testing Frame Dior an example of the results of a full equipment test of a bipolar raw EMG instrument using the EMG Equipment Tester software supplied with the Whisper 200 69 D40 8 00 224g poss Foar fio2450 1024 50 11024 50 11024 50 Results File 990003 res Click on Exit to return to Spot Record Analysis Figure 12 Test results of the full equipment test of a 4 channel raw EMG instrument As you can see four separate EMG channels have been tested Eleven unique parameter values have been calculated for each channel and the impulse response has been recorded This report may be printed out and saved as a record of the test and the EMG system functionality The system performance test The goa
103. which is present in all other tests This allows us to calculate the signal to noise ratio of the EMG instrumentation Testing EMG instrumentation The most important task of an EMG recording instrument is to measure and process EMG signals in a reliable and reproducible manner Using the Whisper Mode 0 and Mode 1 EMG test signals it is possible to check that your EMG instrumentation is working correctly since in these modes the differential mode component will be applied to the EMG instrument under test From the fifteen seconds of recorded EMG a number of parameters can be determined The most important parameters are e The RMS value of the recorded EMG signal e The mean value of the recorded EMG signal e Median and mode frequency of the power spectrum of the recorded EMG signal 14 e Using the Whisper Whisper User Manual The CMRR test Mode 2 can be very informative if you are able to view the live output of the EMG system under test Poor CMRR performance is easy to spot as it produces a large signal output during this test and instantly identifies a problem EMG channel Whisper User Manual Since the precise values of the EMG signal stored in the Whisper are known we can calculate the expected parameter values and compare them to the values that we measure A regular EMG instrumentation test using the Whisper allows verification of the gain the offset and the frequency characteristics of any EMG instrumentation Tim
104. white noise The low pass filter was a 2nd order 80 Hz filter and the high pass filter was a 1st order 40 Hz filter The digital filter used a 1024 Hz sample rate The resulting EMG test sequence has been scaled such that the standard deviation of the amplitude of the sequence equals 200 The overall z transfer function of the digital band pass filter is 0 035719 z 1 0022 z z 1 z 1 97922 1 2948z 0 2804 The simulated EMG data is provided in the file EPROM_e1 DST on the diskettes supplied with the Whisper This file is a standard ASCII file and can be read by many common spreadsheet programs such as Lotus Quattro and Excel etc If the DST data is read into any of these products and plotted then you should get a display that is similar to that illustrated in The y scale values correspond to the amplitude of the differential mode signal at the output of Whisper in microvolts Thus a value of 345 in the data file is converted into an output of 345 uV at the EMG A z 10 e The Test Signal Whisper User Manual signal output The file EPROM_e DST thus provides you an exact description of the standard differential mode test signal The common mode signal The common mode signal generated by the Whisper consists of three parts During the first six seconds the common mode signal remains 0 0 Volt As soon as the differential mode signal starts to output the stored EMG signal the common mode signal becomes a sinusoi
105. ws 95 and 64Mb of memory Analog data recording is a complex subject and it is very helpful to consider all the parameters that may affect your test data before you start to use the Whisper This is especially helpful as most of the parameters that affect the test recordings that you make with the Whisper will also affect your day to day analog recordings in the laboratory It is important to remember that the tests that you will be performing will allow you to investigate the performance on not only your EMG system but also your analog data acquisition system as well as the parameters that you use to sample your analog data during your normal day to day operations Setting the Gain Many EMG systems have a number of different gain settings and it is important to select the optimal gain setting to record the test signals that are produced by the Whisper The largest EMG test signal is produced when the Whisper is in Mode 0 or 1 depending on the type of test that you are performing For a typical surface EMG system this will be a Mode 1 signal which has a maximum differential EMG signal amplitude of 500uV There are three factors that must be considered Electrode gain Both the EMG systems used in this tutorial use pre amplified surface electrodes that have an internal gain amplification factor MA 100 pre amplified electrodes have a gain of x320 while the MA 300 pre amplified electrodes have a gain of x20 It is important to know the gain of

Whisper User Manual - Motion Lab Systems, Inc.

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