EMG force measurement

[ericDev]

Hi,

I am trying to measure an EMG signal. What i want to do is continually sample a signal and when the voltage signal level goes above a predetermined voltage level it triggers a TRUE/FALSE. I am using a USB 6210 for the DAQ and i am using LabVIEW 7.1. Does anybody know the best way to do this or have any other insight. I am new to LabVIEW, any help would be great.


eric

Message Edited by ericDev on 09-18-2006 12:12 AM

[devchander]

This would be my advise.

If it is just a project work related activity, go ahead with a DAQ card

But if you application is something more vital, then it would be advisible to go with specialized instrumntation that satisfies all biomedical signal acquisition requirements.

For starters, you can use either DAQ assistant express VI's ( search for online tutorials on DAQ assistant in ni.com) or voltage acquisition VI's in examples shipped with LabVIEW

Go to Find Examples>>Hardware input outout>>DAQmx>>analog measurement>>Voltage folder and look at acquisition example vi's provided here

the most important thing would be to select an ADC/Analog Input range that is optimal for the voltage range of the signal that you wish to measure

when the voltage signal level goes above a predetermined voltage level it triggers a TRUE/FALSE

for this, in the above progrmas,  just use appropriate comparison function found in block diagram>>functions palette>>comparison functions and compare the read data with our threshold level and output true/false on a LED indicator

[Jennifer O]

Hi Eric,

I just wanted to add a few points to devchander's solution to show you a couple of functions which might come in handy.

1)The DAQ Assistant will return data in a 'dynamic data' type which consists of both data (magnitude) and timing information.  When performing a comparison you can use the dynamic data type, however it will return your answer in a dynamic data type which may not be what you are looking for.  You can use the 'Convert from Dynamic Data' function to convert to either an array or single value.  Feeding the array or single value to the comparison function (i.e greater than) will return a boolean array or boolean data type.

Hint: To locate a function when you know the name, but do not know which pallette it is in, simply click the search button at the top of the main functions pallette and type the name of the function.

2)In addition to displaying the TRUE/FALSE as a boolean indicator, you also have the option of outputting your result to a digital line on your DAQ device to control a physical LED or other indicator of your choice.

3)If you decide to work with arrays in your comparison (i.e. you read 100 data points at a time and would like to have a TRUE value if any one of the 100 points exceeds your limit) you may find the 'Or Array Elements' to be useful.  This is located on the boolean portion of the functions pallette and resembles a backwards 'E'. 

Hopefully this helps,

Jennifer O.