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PWM Measurement with DAQmx 6259

 I am using a DAQmx 6259 card to measure the pulse width modulation on an alalog signal thats abot 1.1KHz.  I am using the "Pules Measurements.vi" to process this signal.  The outputs of this Vi are Period, Pulse Duration, and Duty Cycle.

 

I need help in making a Pulse Width Modulation Measuremnet in milliseconds.

John Kidder
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Hi John,

 

In order to take the measurements you mentioned in your post, I think the easiest way would be to use the example VI called Meas Buffered Semi-Period-Continuous.vi (found in the NI Example Finder). You will have to do a little bit of manipulation to make this work. This example takes the time difference between two consecutive edges of the input signal. So, from this you can derive period, pulse width, frequency, and duty cycle. All of this can be done with some simple math. Also, the output of the DAQmx Read VI in this example is in seconds so you just need to divide that measurement by 1000 to go to milliseconds. 

 

The only thing that you will have to do is to add in a start trigger VI so that you know whether you are starting the acquisition on the rising or falling edge of a pulse. If you set up your start trigger to be rising edge you will know that each new period of your signal will consist of a pulse width measurement and a trough width measurement. From there you should be able to derive all your other measurements. I hope this helps.

 

Chris W

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