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Difference in 5B37 5B30 or 5B40 for temperature measurements

Thread Summary

The user inquires about the advantages of using the 5B37 Isolated Thermocouple Input over 5B voltage modules (5B30 and 5B40) for measuring temperature with a nonstandard Type C thermocouple. The 5B37 integrates Cold Junction Compensation (CJC) and scales the output to 0V at the defined minus full-scale temperature, reducing ambient temperature errors. Using a 5B voltage module requires external CJC measurement and conversion in LabVIEW. Custom 5B37 configurations for Type C thermocouples are available, but inverse polynomials for mV to temperature conversion are not provided.
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I need to measure temperature by nonstandard TC of type "C" the 5B37 Isolated Thermocouple Input.

As I understand, the output of the model is not proportional to the temperature, but has the same linearity as the TC voltage.

So what is an advantage of using 5B37 comparing to 5B voltage modules like 5B40 and 5B30? Is the only difference the Cold Junction Compensation in 5B37?

Alternatively, I can measure 1) the TC voltage amplified by 5B30 and 2) Cold Junction temperature voltage (it is usually about room temperature - some cheap analog sensor) by a 2-channel data acquisition card.

Then in Labview I can calculate the temperature using 6-order polynomial. Am I right?

There is also option to use a special Omega (producer of C-type TC) USB DAQ card, but it has no drivers for LabView and uses 40-years old RTU ModBus Protocol, which requires very low level programming (looks like Assembler).

Also I tried to find an evaluation thermocouple board that supports "C"-type at Analog but could not find anything - only for standard TC.

  • Hi,

    I have moved this thread to the Interface and Isolation community. Someone here should be able to help.

    -Karen

  • Differences between the 5B37 & standard mV modules:

    • Both the 5B37 & the mV modules (5B30 & 5B40) will amplify the Thermocouple signal.
    • The 5B37 module in addition to amplifying the Thermocouple signal, it also integrates the CJC measurement and helps eliminate the temperature of the CJC (Thermocouples Cold Junction). The 5B37 module also scales the defined minus Full-scale temperature such that when the thermocouple temperature is at the defined minus full-scale temperature it will produce a 0V output signal.

     

    Using a mV module for thermocouples:

    • To use a mV module, you would also need to externally measure the temperature of the Thermocouples Cold Junction on the 5B backplane where the thermocouple is connected to the terminal block.
    • Convert the output of the mV module into the temperature equivalent for the thermocouple used.
    • Convert the measurement for the thermocouple Cold Junction into the temperature equivalent for the thermocouple used.
    • Subtract the Cold Junction temperature from the output signal that was converted to temperature.
    • Since the Cold Junction measurement is measuring the ambient temperature changes of the Cold Junction, it is important to make this measurement whenever a thermocouple temperature measurement is made. This helps reduce the error associated with ambient temperature changes during the measurement process.

     

    Although we do not offer any standard ranges for the “Type C” thermocouple, we can build these as a 5B37-Custom configuration, specifying “Type C” thermocouple, temperature range & 0V to 5V output.

     

     

    We do not have the Inverse polynomials for converting from mV into temperature for the “Type C” thermocouple.

  • This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin