Only get accurate thermocouple measurements when set to "Temperature Sensor Disabled"

[saculrotsen]

Hello,

We are currently configuring the SCB-68 Shielded Connector Block to acquire temperature data. There are 5 switches on the block that are supposed to be moved for different temperature sensor types (differential, single ended, etc.). However, we only get accurate data when we configure the switches as "Temperature Sensor Disabled." Using a type K thermocouple with the switches in the differential setting, we were getting around 3000 degrees celsius. When we would turn off signal conditioning, we would get around 20, but it wouldn't adjust  the reading when exposed to heat. When the switches are set to "Temperature Sensor Disabled," we are getting right around 25 degrees celsius, and it increases when we add heat.

So, what are the switches supposed to do if they give us completely wrong data? All of the manuals say to change the switches when using a thermocouple, but that isn't working.

Thank you for reading this.

[_Bryan]

Not much info on your specific setup.

So just taking a guess, but did you configure your device to use the SCB-68 and enable the temperature reference?  You also need to look at the temperature channel setup in MAX to set the correct CJC source.  If you do that don't use channel 0 for differential measurements because the CJC uses that.  There are a few different places that need specific settings to use the SCB-68 correctly.

http://www.ni.com/pdf/manuals/371745c.pdf  (Step 10 - Page 4)

10. (Optional) If you are going to take measurements with an MIO DAQ

device, configure the SCB-68 as an accessory for a DAQ device using

MAX by completing the following steps.

a. Navigate to MAX by selecting Start»Programs»National

Instruments»Measurement & Automation.

b. In the left pane of MAX, expand Devices and Interfaces, then

right-click on your DAQ device and select Properties from the

pull-down menu.

c. Select the Accessory tab from the dialog box, select SCB-68 from

the pull-down menu, then select Configure.

[saculrotsen]

Bryan,

I figured out my problem. I was not aware that the CJC requred the ai0 channel to be not used. The reading was not correct because the thermocouple was plugged into ai0.

Thank you for your help.