Error calculation of temperature reading with NI 9211

[ribfernando]

Hi, 

I measured temperatures of a surface using very fine thermocouple gauges (omega CHAL-001 and CHAL-002) and a NI 9211 board. 
These thermocouples have high impedance. I measured a resistence between 100 and 400  ohm in the thermocouples. 
Gain and offset errors change with the impedance of the thermocouples... 
Is there a way to estimate gain errors knowing the measured temperature, the CJC and the impedance of the thermocouple?

 

Best regards, 
Fernando Ribeiro

[sabri.jatlaoui]

Hello ribfernando,

You’ll find through the below link how to get the CJC for your Module

http://digital.ni.com/public.nsf/allkb/E6DFDA7F1AA16C1C86257599006D4A0A

The related link of this KB will provide you a way to get temperature conversion from CJC.

I wish you a good day, sincerely,

[ribfernando]

Hello sabri.jatlaoui,

First of all, thank you!
I'm not using a RIO system. It's just a NI 9211 and a NI 9162 usb convertor.
I already took the CJC reading from the board. It's not constant at all. What I notice is: CJ potencial is dependent from the time that you start to adquire, and not from the enviroment or thermocouple input.
(see the attached file)
I will use an average value and start from the step 2.

I will let you know if this works for me.

Best Regards,

Fernando Ribeiro