Instruction Manual

HMP230 SERIES
Appendix 9: Re-gaining M210225en-B
146
2. TO BE NOTED IN RE-GAINING
Re-gaining cannot be started automatically or manually unless the
security lock jumper is on. This is to prevent automatic re-gaining from
starting during a sensor calibration (when the security lock jumper must be
removed). Furthermore, re-gaining can be started only if the sensor
temperature is below 100 °C. At higher temperatures the chemicals are
evaporated from the sensor spontaneously, and the re-gaining is not needed.
NOTE
When the transmitter is humidity calibrated, the
possible re-gaining must always be made before it, not
after. Make sure that the temperature of the composite
sensor has come down to normal temperature before
starting a calibration.
Re-gaining can be automatic or it can be started manually. For automatic re-
gaining five parameters are stored in the transmitter memory: the re-gaining
interval, the duration of the sensor heating, the settling-cooling -time, the
difference between the current sensor temperature and the ambient
temperature measured before re-gaining and the k parameter (the power level
the sensor is heated at). The parameter values can be changed by the user. The
factory settings are
Interval min : 720
Duration s : 120
Temp diff : 0.50
Settl time s : 240
k % : 95.00
The time interval between subsequent re-gainings starts at the end of the
settling time.
During heating and settling periods both the analogue and serial outputs as
well as the local display are locked to the values measured before re-gaining
started. The outputs are released again when the sensor has cooled within the
temperature difference setting, or when the settling period has ended whether
sensor has cooled within the temperature difference or not.
The k parameter should not be changed from 95%. The recommended duration
of heating is 120 s and it should not be changed either. The cooling time
needed for the sensor to stabilize to the ambient temperature is strongly
dependent on process conditions, especially on the speed of the air flow
around the sensor head.
The settings for the temperature difference and the settling time should
be determined carefully. If the settling time is too short the sensor is still
warm when the outputs are released and the measured relative humidity value
is too low as the temperature T value is too high. The factory setting (240 s) is