How to get proper thermocouple readings from SCXI-1303 terminal block?

[HW_Autodesk]

Hi,

My question is about the stabalization of my Nanmac 'eroding' thermocouple readings (K-type). Before connecting to SCXI-1303 with SCXI-1102C + SCXI-1000, I measured the K-type thermocouples with Omega thermometer (Model CL23A) which consists with room temperature. But after I connected the thermocouples to SCXI-1303, I found some of them being noise (hardly working).

After reading the 'Incorrect Thermocouple Voltage Reading with SCXI-1303', I realized this might be caused by a ground loop. I removed the bias resistor networks (10 Ω) from the SCXI-1303 (the pullup resistor networks are still there, 10MΩ). Those hardly working channels start to work properly. However, the thermocouples (installed with mould) seem to record constant readings while the machine is molding samples, which should record 50 to 100 degree variations. With the bias resistor networks on in my previous tests, I did observe the phenomena with those working thermocouples.

I chose 'Build in' for CJC choice since I'm aware there is CJC sensor inside. Am I right or is there any setting for chasis SCXI-1000 or the SCXI-1303 terminal block? How will the resistor (bias or pullup) affect the reading?

Best Regards

HW

Best Regards

HW

[HeatherBaker]

Page 2 of the SCXI 1303 manual explains the circuitry of the module.  The field wiring guide also elaborates on the grounding of thermocouples and may provide more insight to why the SCXI 1303 has these built in components.  Page 20 of the SCXI 1102 manual also discusses grounding with the SCXI 1303.  How were you monitoring the values? 

[HW_Autodesk]

Hi,

With the help of those manuals, it seems my SCXI-1303 is working in most of situations. However, it just recorded a constant temperature recently even I tryied different working thermocouples. Then, I found out that my thermos are working properly when I replaced the original SCXI-1102C with SCXI-1102. Afterwards, I changed the 1102c back and it works again.

It looks for me that the replacing procedure is discharging the hardware and reactivate the 1102c again. Is there any way to reset the hardware and make it work normally except swaping the hardware?

Thanks in advance!

HW 

[HeatherBaker · Accepted solution]

I recommend using the bias resistors as recommended in this document.  If it happens again, try resetting the device in MAX by right clicking the device and select Reset Device.

[HW_Autodesk]

Hi, Baker:

Yes, it does the job. Thanks for your help!

Best Regards

HW