On-site relative humidity calibration by Opti-Cal

Opti-Cal offers local calibration for RH sensors, without sending them away to a traceable laboratory or costly on-site calibration services, solving the problems of frequent calibration

For the user of relative humidity sensors there is always a question over the calibration accuracy and stability of the instruments in use.

RH sensors provide economical measurement but require regular calibration and adjustment to ensure correct performance over extended time periods.

It is common for such sensors to require calibration and adjustment at three or six month intervals, depending on the criticality of the measurement process.

Opti-Cal offers the opportunity to provide local calibration of such RH sensors, without the need to send them away to a traceable laboratory or incur the additional cost of contracted on-site calibration services.

For a relatively low capital investment, Opti-Cal will provide calibrations that are directly traceable to International Standards over a wide relative humidity range, and at any set temperature from 10 to 50 C.

Opti-Cal is a portable, fully self-contained humidity/temperature calibrator.

The system comprises a humidity/temperature controlled chamber that can house up to six or more humidity sensors, depending on their physical dimensions.

Temperature and humidity within the chamber are closed-loop controlled and continuously monitored by a precision chilled mirror reference hygrometer.

Opti-Cal works by time proportioning the flows of dry and saturated air according to the pre-selected relative humidity value.

The chamber temperature is controlled by a four-zone Peltier heat pump arrangement for maximum stability and minimum temperature gradient.

The saturator assembly can be filled easily with distilled water at the front of the unit and the easily accessible desiccator can be re-charged by heating when required.

No other maintenance is necessary.

The only external service required is a single phase power supply.

Four wire resistance thermometers for temperature and dew point measurement allow Opti-Cal to provide precise humidity and temperature reference data for the calibration of relative humidity sensors.

System accuracy of +/- 0.2 C dew point and +/- 0.1 C temperature means that an overall uncertainty to better than 2% of measured RH value is achievable.

The in-built reference cooled mirror hygrometer may be calibrated traceable to UK and US national standards and is provided as standard with UKAS certification giving conformity with EA and ILAC.

Bundled with Opti-Cal is a Windows application software suite that allows the user to monitor, chart and log calibration reference data on a PC for later manipulation.

The software also allows control of the reference hygrometer parameters for diagnosis and optimisation, and provides the capability to configure measurement units, analogue outputs and alarms.

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