Non-linear scale issue

[ceilingwalker]

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@Bob_Schor wrote:

I think you might be a little confused.  You mentioned that your amplifier (with its monitor port) can deliver up to 200V.  Then I didn't communicate it correctly. The monitor port is at a ratio of 10mV:1V, with a max output of 2V

What are the characteristics of the amplifier?  Is it a power amplifier, designed to deliver a lot of current to a load? It is a power amplifier that energizes a piezo electric device at a max of 200VDC.

 It might only have a voltage gain of 1 (or less), but still have the characteristics you describe.

The 6002 is well-suited for monitoring this amplifier, as its A/D inputs can accomodate ±10V, which means when your amplifier is maxed out at 200V, only 2V will be presented to the 6002, well within its tolerance.

Bob Schor

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[ceilingwalker]

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@James.M wrote:

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He mentioned "input from an amplifier", so it seems like he is trying to scale a reading of 0-5V to 0-200V within LabVIEW.  I didn't describe this well enough, sorry about that. The power amplifier is driven with a 0-5V signal from the USB-6002. As it drives this amp, the amp has a port on the front of it called "Voltage Monitor". That voltage monitor is what I am trying to scale. The 0-5 output to the amp is done. It's the low voltage monitor from the amp to the USB-6002 card that I am having trouble with. Thank you.

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[Bob_Schor · Accepted solution]

Forgive me for possibly restating the obvious, but here is what I think you are trying to do (now):

You have a USB 6002 that you want to use to measure a signal, in the range 0-2V, from the Voltage Monitor output of your Power Amplifier.

If you set up the 6002 to read voltage, and set it for Differential, 0 to 5 V, unscaled, and have it generate Dbl (or Waveform) outputs, I would expect that when the Monitor Voltage shows 2.0V on the voltmeter, DAQmx will report 2.0V from the USB-6002.

When you hook it up for Differential Input (say Port A0-A4, or whatever the pairing is for Differential), put the Voltage Monitor signal into A0, and the chassis ground of the Power Amplifier on A4.  I'd recommend testing this in MAX before messing with LabVIEW code -- it it much faster, you can easily adjust settings, and then run the Test Panel and see the readings (if you have the wiring backwards, it will be immediately apparent).

Bob Schor