Can the analog inputs be daisy chained to measure higher voltages?

[epsilon-delta]

Can the analog inputs of a PXI-6289 be connected in series to measure higher voltages than normally allowed at the analog inputs of the PXI-6289 (i.e. 10 VDC)?  For example, let's say I wanted to measure 18 VDC using an analog input channel of the PXI-6289.  I would then pick two AI channels and connect the positive of one to the negative of the other and then the two remaining leads would be placed across the 18 VDC.  Resistors could also be placed across the 18 VDC to form a votage divide.  One AI would measure the voltage across one resistor and the other AI would measure the voltage across the remaining resistor.  I have tried this and the voltage measurements appear to loose accuracy.  Thank you for your help.

[Doug_L._Bear]

Hey,

What you are describing is exactly a voltage divider and is exactly how I would recommend you go about what you are trying to read.  You will experience that exact problem though because you are essentially scaling down your voltage to something your card can read at its set number of bits and then having to scale it back up, causing some noise in your reading.

[Rafi2003]

Hi Dough,

How would you measure a high input voltage (10-90).  The voltage is applied to a resistor for loading.

I can not use a voltage divider because it will affect the load resistor. Is there any DAQ card that go to 100V?

What is your suggestion?

Thanks

Rafi

[R Sandoval]

Hello Rafi,

You may want to invest in a high voltage attenuator for signal conditioning prior to reading the signal.  The document below may also be helpful:

High-Voltage Measurements and Isolation

[D Robertson]

Rafi,

I would recommend using a either a DMM (i.e. PXI-4072) or a NI 9225 for cRIO or cDAQ.

Dave