Humidity Sensor or hygrometer measures both moisture and air temperature. The ratio of moisture in the air to the highest amount of moisture at a particular air temperature is called relative humidity. Humidity plays a critical role in achieving optimum quality in drying process, production, packaging, storage and transport for the semiconductor, pharmaceutical, medical and food industries. Other common usage includes heating, ventilation and air-conditioning (HVAC) applications.
Displacement Sensor – a strain gauge or other mechanism to measure expansion or contraction of a material in proportional to changes in relative humidity. Psychrometer or wet-dry bulb, uses 2 matched thermometers over which air is drawn, with 1 thermometer’s bulb covered by a wet cloth or wick, the difference in reading is then calculated to determine relative humidity value.
Polymer Resistive Sensor – measures the electrical impedance or resistance of a hygroscopic medium such as conductive polymer, salt or treated substrate. Resistance change inversely with humidity. Capacitive thin-film polymer sensor – measures the capacitance of an electrode where a polymer acts as the dielectric portion of the capacitor. It changes proportional to changes in relative humidity.
Humidity sensor accuracy will drift due to constant temperature changes and exposure to airborne contaminants. The only way to know if your humidity sensor has drifted is through calibration.
Metcal can provide ISO 17025 accredited humidity sensor calibration from 11 to 98 %rh, with best uncertainty +/-1.1 %rh.
Calibration options include Primary Fixed Point method or Comparison method with 0.01 %rh high accuracy humidity transmitter in our laboratory or on-site.
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