Using the NI9205 with a Load Cell

[KurtzC1]

Hello Everyone,

I am using an NI9205 to gather voltage data from a Robot Shop S load cell. The reason I am using a NI9205 is because it’s range goes down to millivolts, making it great for load cells. The issue I am having is when I initialize my task and run the VI, the NI9205 does not output millivolts. Instead it outputs microvolts or even smaller. Loadcells are supposed to output voltage in the millivolt range. I tried multiple methods for initializing the NI9205 and none of them outputted millivolts. The methods I tried are shown below.

The final method I tried gave me an error, which is also listed below.

Any information would be appreciated in trouble shooting this issue!

Error -200431 occurred at DAQmx Create Channel (AI-Force-Bridge-Two-Point-Linear).vi:3350002

Possible reason(s):

Selected physical channel does not support the measurement type required by the virtual channel you are creating.

Create a channel of a measurement type that is supported by the physical channel, or select a physical channel that supports the measurement type.

Property: AI.MeasType

Requested Value: Force:Bridge

Possible Values: Current, Resistance, Strain Gage, Temperature:Built-in Sensor, Temperature:RTD, Temperature:Thermistor, Temperature:Thermocouple, Voltage, More:Voltage:Custom with Excitation

Task Name: _unnamedTask<7F>

[ARVega]

Hi KurtzC1,

The NI-9205 module is not recommended for this type of measurement (AI-Force-Bridge-Two-Point-Linear). Here you can find the modules that support that type of measurement: https://www.ni.com/en-us/shop/category/strain-pressure-and-force.html

The error message you get is the LabVIEW way to tell you that what you want the task to measure, does not match the features supported by your hardware channel.

Best,
Anyela V.

[KurtzC1]

Conceptually, "Why is it not compatible?" My professor said the NI9205 can be used with loadcells, because it can accurately read millivolts. Also, "What instruments should I be using with the NI9205?" 

I am pretty sure my school has a NI9219 that I can use. Which solves my DAQ compatibility problem. 

[RavensFan · Accepted solution]

Load cells need a ratiometric measurement.  That means output/input.  Modules that can read load cells will supply a know excitation voltage, or sense the excitation voltage applied.  The 9205 doesn't do that.

[KurtzC1]

Thank you for the response. So the NI9219 will be able to sense my 5V excitation? 

[RavensFan]

Yes.  http://www.ni.com/pdf/manuals/377223a_02.pdf