OptiCal Humidity Calibrator

The OptiCal is a premium, self-contained calibrator for humidity sensors. It features an integrated chilled-mirror reference which enables the operator to perform calibrations that are traceable to national standards.

The calibration chamber accommodates up to 5 probes or sensors of any brand or model. The chamber is insulated, and temperature controlled for maximum stability and minimum temperature gradients



Simple operation and maintenance

Excellent chamber stability and uniformity

Built in precision chilled mirror reference instrument

Generate 10 to 90% RH over +10 to +50°C (+50 to 122°F) temperature

Manual control or optional straightforward automated set point programming

Transportable to allow on-site calibrations

Generated range10 – 90% RH
Control element accuracy≤ ±1% RH (10-70% RH)
≤ ±1.5% RH (70-90% RH)
Stability±0.2% RH (20-80% RH)
Generated range+10 to +50°C (+50 to +122°F)
(lowest T set point = 10°C (18°F) below ambient)
Accuracy±0.1°C (±0.18°F)
Stability±0.1°C (±0.18°F)
Ramp rate from
+20 to +40°C (+68 to +104°F)1.5°C / minute (2.7°F / minute)
+40 to +20°C (+104 to +68°F)0.7°C / minute (1.2°F / minute)
Control elementRemovable relative humidity sensor
Dew Point±0.2°C (±0.36°F)
Temperature±0.1°C (±0.18°F)
Measurement units
Dew Point(°C/°F), % RH
Temperature(°C/°F), gm-3, gkg-1, water activity (aW)
Analog4-20 mA or 0-20 mA over user-settable output
Accuracy±0.2°C (±3.6°F)
Digital500 Ω maximum load resistance
AlarmRS232 @ 9600 baud rate
Volt free contact, 30 V, 100 mA maximum
Probe portsUp to 5 – sensor body diameters 5 to 25mm (0.2 to 0.98″) accommodated by port adapters
Chamber volume2000cm3 (112.1in3)
Chamber dimensions105 x 105 x 160mm (4.13 x 4.13 x 6.3″) (w x h x d)
Set-point resolution0.1 for humidity and temperature
Displays2 line Vacuum Fluorescent Display
Instrument dimensions290 x 520 x 420mm (11.4 x 20.5 x 16.5″)(h x w x d)
Weight20kg (44lbs)

The OptiCal is a premium calibration solution for humidity sensors. The stand-alone and transportable calibrator requires no external services other than mains power, and features an integrated chilled mirror reference instrument to enable the operator to perform calibrations that are traceable to national standards.

The calibration chamber features 5 interchangeable ports to accommodate virtually any brand, type or model of sensor. The environment within the insulated calibration chamber is temperature controlled using a 4-zone fan-assisted Peltier arrangement for maximum stability, and minimum temperature gradient. The humidity of the circulating air is precisely regulated using a closed-loop control system that functions by proportionally mixing flows of dry and saturated air.

A bright and clear VFD (vacuum fluorescent display) displays the parameters measured by the reference instrument in various relative and absolute humidity units, alongside the temperature within the chamber.

The humidity and temperature set-points can be controlled either manually or automatically as part of a calibration program. Manual control is achieved by the switches on the front panel and response time to a humidity or temperature step change is typically quicker than 10 minutes. The supplied application software allows calibration programs to be created, enabling automatic time-based control of temperature and humidity set points. The software also allows the user to monitor, chart and log calibration reference data on a PC for later analysis.

The OptiCal is supplied with an integrated Optidew chilled mirror reference instrument with traceable calibration to national standards, which provides measurement integrity and traceability for the sensors being calibrated.

The desiccant changes color to indicate when it needs to be recharged, and is visible through a clear window on the front of the unit. Recharging the desiccant is simply a matter of heating it in a conventional oven at +150°C (+302°F) for 3 hours. The water reservoir at the front of the unit shows the current saturator fill level, and makes it easy to top-up with distilled water when required. No other maintenance is necessary, apart from periodic calibration of the chilled mirror reference.

Supply85 to 264 V AC, 47/63 Hz, 150 VA

Calibration of humidity and temperature probes

The application software is an interface to the OptiCal. It provides a display of the measured and calculated parameters, system status, charting and logging, statistical information and a facility to view and change the system parameters.

Additional information





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