An optional combined humidity and temperature probe can be connected to the rear of the HFRR control unit. For some test procedures, the wear scar must be adjusted to compensate for the effect of fuel moisture content on the result. The probe will automatically measure the ambient temperature and humidity at the start and end of the test, instead of the user having to take the measurements manually.
If the instrument is being used with a humidity controlled cabinet, the probe should be located in the fitting provided on the left side of the cabinet. If the instrument is not being used with a humidity controlled cabinet, a bracket is supplied with the probe, enabling the probe to be connected to the side of the mechanical unit.