Measure voltage between two thermocouples without introducing a new probe

[RTSLVU]

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@kkofori wrote:

truth be told I am just reading thermocouple voltage and not measured voltage I was advised to do it this way. As an extra probe might bring error to the set up. My professor said it should be done with just the thermocouple probes and I am still unsure how thermocouple probe can also measure voltage and not just read generated thermocouple voltage

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Well not really... I mean sure thermocouples are just wire, but the input to each channel is a differential input so if you set the channel to read millivolts DC you would get the raw thermocouple voltage but not the voltage on the device. 

Is that what you are looking for? 

[RTSLVU]

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@kkofori wrote:

really but when my code is running I can see it quickly flicker from celsius  to mV on the daq screen per each channel. Is this evidence that both is working or not?

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Attach your VI, I want to see this for myself

[kkofori]

i am looking for the voltage of the device not the raw thermocouple voltage

[kkofori]

here is the code

[RTSLVU]

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@kkofori wrote:

i am looking for the voltage of the device not the raw thermocouple voltage

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Well you are not going to get that because of what I said before about the differential input is only going to measure the raw thermocouple voltage.

[kkofori]

oh okay thank you for letting me know. I think I will introduce voltage probes on a different channel.  I think ive been led astray for think I can use two thermocoupoles as positive and negative probe voltage probe wires to read voltage

[kkofori]

I have two thermocouples T1 and T2 and i have a keysight Daq 973 . I have a labview code to find the temperature gradient , T1-T2 , i also want to find the voltage gradient between those two points without introducing a voltmeter . is that possible or do I need to add an additional voltmeter between those points

[GerdW]

Hi kkofori,

you asked the same question weeks ago: what have changed since then (and why do you think you need to start a new thread)?

[kkofori]

Because people in my circle keep insisting there are solution to that 

[RTSLVU]

Okay I just reread this thread and I may have misunderstood your original question.

You have two thermocouples, TC1 and TC2 on two different points and you want to measure the voltage between those two points using the thermocouples. Correct?

I still do not believe this is going to be possible because DAQM901A multiplexer has isolated differential inputs. So you cannot measure the voltage between two channels because they are isolated from each other and isolated from ground.

To do what you want, you need to measure the voltage on each point in respect to ground and calculate the difference.

As I explained previously the two inputs that thermocouples are on will only be measuring the differential voltage between the two thermocouple wires that the thermocouple generates (mV/Degree) and converts it to Degrees.