Questions on Temperature Measuring Devices

Interview Questions Instrumentation
1

List of Questions and answers on Temperature Measuring Devices used in temperature measurement.

  1. What is a thermocouple and how is a thermocouple constructed?

  2. Explain briefly how a thermocouple can be used to measure a process
    temperature.

  3. Why are extension grade wires needed when connections have to be made
    between the thermocouple and the temperature transmitter?

  4. What full scale mV range should be specified for a J-couple installation with
    a constant cold junction of 30 C and a hot junction which ranges from 30 to
    250 C?

  5. How is an RTD constructed?

  6. Explain briefly how an RTD can be used to measure process temperature.

  7. Sketch a simple wheatstone resistance bridge circuit to show how an RTD
    temperature value can be sensed.

  8. Revise the diagram of question #7 to show how a three lead connection is
    used to minimize RTD errors due to lead wire resistance changes.

  9. Why are temperature sensors such as thermocouples and RTDs mounted
    in thermal wells? How does the use of a thermal well effect the response of
    the temperature sensor?

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