| The role of humidity calibrations that are accurate, reproducible, and documentable is becoming more and more important. ISO quality guidelines and regulations according to FDA guidelines in the pharmaceutical industry, etc., require that humidity instruments have a traceable, accurate calibration. The humidity calibrator HUMOR 20 developed by E+E is the ideal reference instrument for these requirements. The HUMOR 20 can be used in the humidity range of 10-95% RH both for monitoring cylindrical sensors (transmitters, hand-held instruments,...) and also for monitoring instruments with cubic dimensions (data loggers, wall instruments,...). A temperature sensor integrated in the measurement chamber also permits the monitoring of an optional temperature output. The HUMOR 20 is traceable to international standards and can be delivered with an official, internationally recognised OEKD calibration certificate. Due to its high accuracy, the HUMOR 20 is the basis for accredited calibration laboratories for relative humidity. Based on its operating principle, the HUMOR 20 can be used under typical conditions in a laboratory climate. This means that expensive, fully air-conditioned rooms are not necessary. For operation HUMOR 20 requires only distilled water, filtered oil-free air with a pressure of 10 bar and a power supply between 90-230V AC. The specimen can be powered by 24V DC that is available directly on the HUMOR 20. A software package included in the scope of supply allows the user to record the calibration process and to adjust the HUMOR 20. The connection to a PC is realised over a typical RS232 interface (COM port). Operation: The operation of the HUMOR 20 is based on a fundamental two-pressure process and thus is similar to instruments used in national bureaus for standards. Air or nitrogen at a pressure p1 is led through a waterfilled saturation chamber and saturated to 100% RH at p1. By means of a reduction valve, the saturated air is reduced to the ambient pressure p and fed into the measurement chamber. Due to the construction, the saturation chamber and the measurement chamber are at the same temperature. Under these conditions, the water-vapour partial pressure ews is reduced at the same ratio as the total pressure. Essentially, the following applies: e = ews * p / p1 From this it follows that: RH = e / ews = p / p1 Thus, the generated relative humidity essentially depends on the ratio of the two pressures. Construction specific deviations from this ratio are corrected during factory adjustments. B | 
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