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Humidity Calibration Instruments

Heating, ventilation and air conditioning systems control the climate within buildings. When the temperature inside a building climbs, but the relative humidity remains low, water rapidly evaporates and can cause problems with mold, decay and corrosion. Relative humidity -- measured by a hygrometer, which requires regular calibration -- plays a role in health care, safety standards for individuals and the technical requirements for safe use of machinery and vehicles in industry.

  1. Two-Pressure Humidity Calibrator

    • The "two-pressure" humidity calibration system involves two chambers, one within another. The process saturates air or nitrogen with water vapor at a controlled temperature and pressure, with the saturated, high-pressure air going from one chamber to another via a pressure-reducing valve. The air is then isothermally reduced to test pressure at the given test temperature. The Kaymont Humidity Calibrator M2000, for example, allows for calibrations of chart recorders using remote probes, or a simultaneous linearity test of multiple data points. Reaching equilibrium within minutes, it ranks as the fastest tool for a full range of calibration. Its speed allows for continuous calibrations of hygrometers, making it a common fixture in laboratories.

      The M2000 measures and regulates relative humidity directly, eliminating the need for error-prone conversions and computations. Two air pumps control the internal system: One pump uses dry air, while the other one uses wet air. The controllers can then call for either pump to respond accordingly, which greatly speeds up the calibration process, according to its manufacturer.

    Saturated Salt Solutions

    • Using saturated salt solutions to calibrate humidity involves a closed box partly filled with the solutions, generating relative humidity in the area above the salt. This method, while independent of environmental temperature, remains strongly dependent on system temperature uniformity. The most accurate results using saturated salt solutions for humidity calibration require a temperature uniformity of 0.5 degrees Celsius, reports JLC International.

    Consultant Services

    • For large-scale humidity calibration projects, the Danish National Reference laboratory for humidity measurements provides services to assist in the calibration process. The laboratory utilizes the two-pressure system, and offers consultant services for humidity measurements and calibrations. It also features assistance in sensor development and large calibration spaces for multiple instruments.

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