MICHELL Instruments, represented by Lear Siegler , has released a low cost, easy to use and fully integrated system for the calibration of dew point and relative humidity sensors from 2 to 90% relative humidity, -30º to +20ºC dew point.
Operation of the HG-1 humidity calibrator is based on a simple yet reliable principle.
A source of dry air is split into two streams, one of which is humidified by bubbling it through a water saturator.
The two air streams are then volumetrically mixed to produce a resultant airflow of variable humidity dependent upon the mixing ratio selected on the HG-l's front panel-mounted flowmeters.
The standard HG-1 includes an integrated air pump and single column, indicating re-chargeable desiccant cartridge. In single-pass mode this arrangement will give days of operation at a minimum dew point of below -30ºC.
The HG-1 also has the facility to input dry air or calibration gas, such as bottled nitrogen, to boost its low-end capability down as low as -40ºC dew point.
The integrated test chamber can accommodate up to six humidity sensors simultaneously. The Dewmet reference sensor is also located within the chamber.
It is very important that the cooled mirror dew point hygrometer reading be used as the reference value. This is the calibrated device - the generator setting values are only approximate and will vary depending on exact operation conditions.
As an alternative to the integrated calibration chamber, the HG-1 can be supplied with only a gas-outlet feed to supply calibration air to an external sensor or system.
Optionally, the HG-1 can also be supplied with a separate re-circulating temperature control bath to allow humidity calibrations to be performed at temperatures other than the prevailing ambient.