Analog inputs voltage effected each other

[erinç]

Hi,

I'm using a NI PCI-6070E adc card with a sc2345 series carries. Now two channels are used, one of them is 1-Channel Thermocouple Input Modules (SCC-TC02) the other one is differential input (+10 V, -10 V; without any module). When differential input goes +10 volt or -10 volt level suddenly, temperature measurement is effected and goes crazy. I want to solve this problem. Thank you in advance. 

[ColeTrain]

Hello erinc,

The 6070E channels are not completely isolated from each other and since your thermocouple measurement is very low voltages, a little noise will throw off your accuracy considerably.  Try moving the ±10V signal to the channel furthest away from your thermocouple and see if that helps at all.  

[erinç]

Hello ColeTrain,

Thank you for your quick suggestion. I've already tried that but it did not work.

[nayer]

Hey,

Here is a another thing you can try, 

Connect - Thermocouple to Channel 0

Connect Channel 1 - AI Ground

Connect 10V diff signal to Channel 2

Conncet Channel 3 - AI Ground.

This will provide path to the internal capacitor for S/H ckt to discharge and will remove ghosting. Look at this knowledgebase for more information.

Thanks

NI-khil

[ColeTrain]

NI-khil,

Thanks for the KB, but the link happens to be internal to NI.  For anyone outside of our network, you can go here to see the KB NI-khil posted.