cjc daqmx scxi

[didje]

Hello

I'm using a SCXI, 1125 modules with 1320 connectors to read thermocouples with labview. My cjc is done using the built-in sensor

I can read all my channels and the cjc with Daqmx. However when I'm reading the output at the back of the 1125 modules, channel 0 is saturating when cjc is used by Daqmx and reads 0.5V when I ask daqmx to read cjc.

I would like to send at the back, my input voltage amplified on some modules and cjc on one other.

Is it possible to do it without going back to Traditional Daq?

Thanks

Etienne

[SachaE]

Hi,

  to read off the back of the 1125 directly, have you got the module set for parallel mode, and None for the cabled device, however from the manual here : http://www.ni.com/pdf/manuals/322425a.pdf

You can configure the SCXI-1125 to operate in parallel mode as described in Chapter 1, Installing and Configuring the SCXI-1125. Using this mode of operation, all eight analog output channels on the SCXI-1125 are connected to eight analog input channels on the DAQ device. In this mode, the CJC channel is not accessible. Every SCXI-1125 configured for parallel mode must have a DAQ device directly cabled to it.

To make this work in parallel, you need a second DAQ card, one dedicated board for the cascading portion of the system and one to make the 1125 configure in parallel mode. Although not connected to a DAQ device, the SCXI-1125 will need to be configured in parallel mode, connected to "None" in the Measurement & Automation Explorer (MAX). It needs to be configured this way in order for the input signals to be present at its rear connector (see the manual for pin assignments figure 2-6).

This configuration is not supported by National Instruments however.

Can you let me know exactly how you have the module(s) configured in Measurement and Automation explorer?

Thanks

Sacha Emery
National Instruments (UK)

[didje]

Hi,

In Max All my SCXI are configured in multiplexed mode, My SCXI 1001 chassis is controlled by a 6251 card connected to module1(a SCXI 1125).

I would like to get with Daqmx the reading for the thermocouples connected to the 1125 and also the CJC temperature (I've reserved one channel for this). My measurement once conditioned by the scxi will be sent to a dewetron. I would like to send the 8 amplified temperature for some modules and for one of them the reading of the CJC sensor and 7 thermocouples readings.

I've noticed that when using the module in multiplexed mode the back connector voltage corresponds to the one that is amplified, however if I'm using the Cjc sensor, it will be impossible to read channel 0 instead a voltage of 0.25V in some case and 0.47V in other will be read.

Thanks

Etienne