The client’s instrument is subjected to a three (humidity) point calibration at a specified temperature, typically 20, 50 & 80%RH with a minimum “soak”, or equilibration time of two hours at each value, with the sensor(s) exposed to a moving air stream of controlled humidity and temperature at a velocity of 20 liters per minute. These ‘As Found’ indications of the instrument are evaluated for compliance with required tolerances. If needed, and appropriate for the instrument, adjustments are performed to optimize the instrument’s indications and the test is repeated to determine ‘As Left’ indications.
