Correcting humidity is much more difficult than correcting the temperature. Temperature calibration often uses a standard thermometer as a standard, and the calibration standard of humidity is difficult to achieve. Dry and wet bulb thermometers and some common pointer hygrometers cannot be used for calibration, and accuracy cannot be guaranteed because of their requirements. The environmental conditions are very strict. In general, (preferably in a suitable environment for humidity), in the absence of a complete calibration device, a simple saturated salt solution test is usually used and the temperature is measured.

Humidity correction

At present, humidity sensor probes generally have poor interchangeability, and the same type of sensors cannot be interchanged, which seriously affects the use effect. Difficulties have been added to maintenance and commissioning. Some manufacturers have made various efforts in this regard (but the interchangeability is still very poor) and achieved good results.

Interchangeability

When a DC voltage is applied to a moisture sensitive material such as a metal oxide ceramic, a high molecular polymer, or a lithium chloride, it may cause a change in performance or even failure. Therefore, such a humidity sensor probe cannot use a DC voltage or an AC voltage having a DC component. Must be powered by AC.

Humidity sensor probe power supply

In addition to being sensitive to ambient humidity, humidity sensitive components are also very sensitive to temperature. The temperature coefficient is generally in the range of 0.2 to 0.8% RH/°C. Moreover, some humidity sensors have different temperature coefficients at different relative humidity.

Temperature drift is nonlinear, which requires temperature compensation on the circuit. The use of single-chip software compensation, or humidity sensor probe without temperature compensation, can not guarantee the accuracy of the full temperature range. The linearization of the temperature drift curve of the humidity sensor directly affects the compensation effect, and the nonlinear temperature drift often does not compensate for the better effect.

Only the hardware temperature follow-up compensation will get the real compensation effect. The temperature range in which the humidity sensor probe operates is also an important parameter. Most moisture sensitive components are difficult to work properly above 40 °C.