Temperature conv. subvi

[Tripepperoni]

Well, decimal point sounds much better than comma 😄 I keep your advices in mind and I thank for them. My "experiments" will be conducted only during the day and won't last longer than 8 hours 🙂

[Tripepperoni]

I'm sorry for double-posting but I got one, last question connected with this topic. The structure mentioned in the first post here, linearizes measured temperature. What if my op amps have already done the linearization by themselves ? Is double linearization ( op amps and block ) able to interefere enough to give wrong temperature ? I haven't checked yet if it's the software issue or hardware ( maybe TC are faulty ) but I get wrong temperatures.

Op amps give 100 times gain, but I have to divide my signal by 30 000 to get temperature at the level of 20 degC. I haven't checked if the new value in the divide block gives proper readings because further tests are neccessary.

[johnsold]

If your op amps have done the linearization, that is called "signal conditioning." Most signal conditioning systems also handle the CJC issue. Are you sure that your external circuit does not do that as well?

Once the voltage signal has been "linearized" it is no longer obvious how to apply CJC to the result unless you know the algorithm used by the linearization process.

Lynn

[Tripepperoni]

Well, my op amps should take care of cjc so you suggest that I should get rid of cjc from the thermocouple subvi, right ? Like in the picture below. ( I don't know the algorithm )

[johnsold]

The VI you show in the picture converts thermocouple voltage to temperature. It has nothing to do with CJC. Its algorithm is described on its front panel, in the Context Help, and on the block diagram, although you do need to read the referenced NIST document for all the details.

You need to check the documentation on the signal conditioning circuit you are using or check with the party who designed and built it to find out what it actually does. Then you can decide whether you need to do CJC and how to go about it.

Lynn