Measuring Strain gauge excitation voltage

[harry-stone@idexx.com]

I have connected my 9237 to a 9945. I am using a 350 ohm strain gauge. I have the set excitation voltage to 2.5V in MAX. Is there a way to physically measure to be sure it is 2.5V? Also, in my vi I am using a DAQmx create channel function. I want to add another channel to this but cannot see how to do it.

thanks

HS

[Paul-D · Accepted solution]

Hi Harry, this is Paul with Applications Engineering at NI.

My first question is why you are wanting to physically measure the excitation voltage?

If you are wondering how that voltage could vary, it is limited by the 150mW max output of your device, as explained here:  http://digital.ni.com/public.nsf/allkb/7CBC67482CC9FB318625758C0048FF73?OpenDocument

If you still want to measure it externally, you would have a couple options.  You could use another DAQ device to measure the voltage, or you could use another external device like a digital multimeter.

If you want to verify in LabVIEW code the excitation that is actually being provided, you could use the DAQmx Property Node "Actual Excitation Value".

As far as reading multiple channels, theres a couple ways you can go about this.  If your channels are sequential and all have the same settings, then you could change your Physical Channel Name from something like "Dev1/ai0" to "Dev1/ai0:3: to specify the first 4 channels.  Alternatively, if you wanted to select non-sequential channels you can chain create channel tasks together, as long as they are the same type of task (AI Voltage, etc), and off the same device, as pictured below.

Let us know if you have any more questions.

Regards,

Paul