Waveform capturing

[james_p_martin]

Hello All,

I am required to capture the ringing waveform (which is generated when we do surge tests on coils) due to effect of inductance of the coil......so in my application I am switching a Glass relay to apply a high voltage on coil and acquiring the waveform.....but even ater scaling and all ....I am just getting mVolts data.....which is very less....because I should get aroung 240-289 V which I am not able to capture....I am using 6221 Card....I am thinking that what I am getting is the last part of dying waveform(thats why millivolts I am getting).

Could any body please suggest some solution.

Regards

James

[tbd]

Hi James,

      The specs for the PCI 6221 list its analog input range as +/-10V - with damage possible above 15V (25V while powered.)   One question is how the 289V signal is being conditioned prior to connection to the 6221.  If you have an Oscilloscope handy, verify that there's a wavform to capture.  Verify that the wiring matches the DAQ channel & hardware-configuration (for instance, if configured for differential-input, are you supplying both +/- inputs ?.)  Assuming your board is [still] working, this sounds like a simple acquisition!   - have you tried using any of the waveform data-acquisition examples that come with LabVIEW?

If you get one of the DAQ examples working, but not your own code, try posting the code that's not working.

Good - luck, and I'm hoping your 6221 is OK!

Message Edited by tbd on 07-05-2006 12:49 AM

[james_p_martin]

Dear Friend,

I have converted that voltage to 0-9 Volts Input then I m feeding it into the card,.......so nothin gonna happen to my card...anyways....thanks for ur reply.......but do u know  about Ringing waveforms which occur when u discharge a capacitor throgh HV stator coils.....which I am going to capture whose rms value will be in 240-289 Volts range.

regards

James

[tbd]

Hi James,

      I'm not an expert on "ringing-waveforms" (neither do I know much about quantum mechanics,) but I can help you acquire an analog waveform using NI data-acquisition products.  I might have a few basic questions like: what's the highest frequency-of-interest in the signal being measured?  What's the voltage range of the signal (0-10V), and how will the signal be [ground] referenced?  How is the data-acquisition being triggered?  Though unlikely, the signal's source impedance could also be important.

Try to set the DAQmx sampling frequency at least 5-times higher than the waveform you want to reproduce (the higher the better).  If you can't make one of the shipping DAQmx examples work, the two most likely causes are: no signal at connection to DAQ hardware (check with scope), or there's a hardware configuration problem.  Try putting a constant 5V on the input channel, ground a different channel, then make sure you can "see" (capture) these two levels where they're supposed to be.