Selected wrong thermocouple type

[flo87]

Dear all,

I erroneously selected the type J thermocouple instead of type K when using the NI USB-TC01. I would really be happy, if anyone could tell me, how I can now calculate the correct temperature from my measurement data?

[SteveD123]

Step 1: Google "type j thermocouple characteristic".

Step 2: Find this amazing reference document: https://www.omega.com/temperature/Z/pdf/z021-032.pdf

Step 3: Find the polynomial terms for a J type and a K in Table 4 on page Z26

Step 4: Derive the original sensor voltage using the J terms and recalculate the temperature using the K terms.

I do not know whether the cold junction compensation needs to be looked at as well.

[flo87]

That's my main problem: Which temperature is assumed for the cold junction?

[Henrik_Volkers · Accepted solution]

all TC conversion polynomes are already available in LV 🙂

And shure, you need at least a good guess of your CJC temperature 😄

I added a vi to correct and get an idea how big the error due to wrong CJC migth be.

[flo87 · Accepted solution]

Vielen Dank, Henrik!

Meanwhile I found, that there is a temperature sensor inside the NI USB-TC01 measuring the cold junction temperature to compensate it. And it seems like the electronics around the cold junction create a quite stationary temperature somewhere at 32°C after some warm-up time.