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How to measure the temperature in a Column Heater Module (CHM) - WKB746

Article number: 746


Measure the temperature of the external column heater known as the Column Heater Module (CHM).


  • Temperature Control Module II (TCMII)

  • Column Heater Module (CHM)


NOTE: There is no Waters qualification document for the external column heater known as the Column Heater Module (CHM). The column heater compartment is designed for higher-flow-rate columns with high heating capability. No published specification covers the measurement of temperature accuracy in this compartment. Use this information to better understand the function of this legacy-design column heating system.

  1. Remove all column hardware when performing thermal measurement.
  2. The CHM is a conduction device, so you need to coat the probe tip thermal conductive paste (heat sink paste) to ensure the best thermal transfer. If no thermal conductive paste is available, add an additional 2 degrees C to the pass/fail criteria.
  3. Tape the probe near the location of the internal probe—3 inches from the end, away from the tubing in the middle, 2 inches from the side wall.
  4. Appropriate measurement windows:
  • +2 / -4 degrees C up to 60 degrees C
  • +2 / -6 degrees C for values above 60 degrees C (using thermal paste)

Note: Measurement device error must be less than or equal to +/- 1 degree C. The criteria window must be increased if measurement devices are less accurate. If a type K probe is used, allow an additional 2 degrees for the probe.


When taking measurements, allow sufficient time for the compartment to reach the set point and stabilize:


  • Allow 20 minutes maximum for the CHM to reach 50 degrees C

  • Allow 40 minutes maximum for the CHM to reach 100 degrees C

  • Allow 60 minutes maximum for the CHM to reach 150 degrees C

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