Overly noisy signal with NI 9218 in +/-65 mV configuration and a load cell powered with external excitation voltage

[captainmurb]

Hi all, 

I am attempting to take a measurement from a loadstar RAS1 load cell on my NI9218 (dsub) in a cRIO 9040 chassis. The cRIO chassis is powered by a 24V power supply. The loadcell is powered by a separate power supply set to 10 volts. The signal+ wire is connected to pin 6 on my dsub 9218, the signal- wire is connected to pin7, and pins 7 and 3 are also tied together. I have attempted multiple software setups and all result in readings that are extremely noisy and unresponsive to me stressing the load cell and are also unresponsive to me turning down the voltage on the power supply. The weird part is, when I measure between pins 6 and 7 directly using a voltmeter, I get a stable 1mV reading which responds to both varying the power supply and applying pressure to the loadcell. What is cause so much noise in the modules readings and how should this setup be done for sensible readings? You may also notice that the excitation voltage source is set to none. If I set it to internal I get the same results, and if I set it to external it throws an error saying given value: external, possible values: Internal, none. 

Thank you for your thoughts!

 NI MAX Test PanelLabview Test

[santo_13]

9218 doesn't support external excitation for bridge measurement. For optimal bridge measurements, the DAQ must be able to read back the actual excitation to convert the measurement to V/V instead of absolute V.

Are you able to switch the DAQ card or the load cell to get better results?

[captainmurb]

I can switch out the module for something else. What would be the right module to read my signal? My load cell outputs 3mV/V and uses 10-12V excitation. Is there any module that can read this kind of signal without using external amplification on the signal? 

Best,

[captainmurb]

Greetings, 

I am attempting to read a 3mV/V output from a loadcell into my cRIO. It requires 12V excitation. I am using a 9218, but have found that for full bridge, the module cannot support external excitation. Additionally, it looks like the 3mV/V signal is too small to get a stable reading. What is the appropriate module to handle a 12V excitation, 3mV/V loadcell, and is there any module that can do this without using an amplifier on the signal first? 

[ZYOng]

NI-9237 supports external excitation of up to 10V and comes with an input range of +/-25mV/V

[santo_13]

Duplicate/extension of https://forums.ni.com/t5/LabVIEW/Overly-noisy-signal-with-NI-9218-in-65-mV-configuration-and-a/m-p/4...