The classification of the humidity sensor and moisture characteristics of humidity sensors, divided into two kinds, resistive and capacitive the basic form of product is formed in the substrate coating moisture material moisture film.
Water vapor adsorption on feeling after wet materials in the air, the impedance of the parts, the dielectric constant of the great changes happened, thus made bench centrifuge wet sensitive components.
Each manufacturer has different levels of humidity sensor products both at home and abroad, the quality price difference is bigger, the user how to choose the ideal * optimal price-performance products have certain difficulty, need to have a understanding in this respect.
Humidity sensor has the following characteristics: 1, the accuracy and long-term stability of the humidity sensor accuracy should be + / - 2% ~ + / - 5% RH, to reach this level it is difficult to used as measuring instruments, the humidity sensor to achieve the accuracy of plus or minus 2% ~ + 3% RH is relatively difficult, usually feature is given in the product information at room temperature (
And clean gas measurement.
In be used actually, because of the influence of the dust, oil pollution and harmful gas, use a long time, will produce aging, precision, accuracy level should combine the long-term stability of the humidity sensor to judge, in general, the working stability of temperature and humidity meter internal humidity sensor and service life is the key to product quality, average temperature and humidity meter, the temperature in the error of plus or minus 1 ℃, humidity in the error of plus or minus 5%.
2, the temperature coefficient of humidity sensor wet sensitive components in addition to the humidity sensitive to the environment, is also very sensitive to temperature, its temperature coefficient is in commonly 0.
2 to 0.
8% RH / ℃ range, and some wet sensitive components under different relative humidity, its temperature coefficient and difference.
Temperature drift of nonlinear, this need in the circuit with temperature compensation.
By single chip microcomputer software compensation, or without temperature compensation of humidity sensor is not the full temperature range of the precision of the linearization of the humidity sensor temperature drift curve directly affect the compensation effect, the nonlinear temperature drift compensation is not often good effect, and that only follow sex USES the hardware temperature compensation will get real compensation effect.
Humidity sensor working temperature range is also important parameters.
Most of the humidity sensitive components in 40 ℃ above the normal work.
3 power metal oxide ceramics, humidity sensors, polymer and lithium chloride humidity sensitive material applied dc voltage, can lead to performance change, even failure, so this kind of humidity sensor can't use dc voltage or dc component of ac voltage.
Must be an alternating current power supply.
4, interchangeability, at present, there is a widespread phenomenon of poor interchangeability humidity sensor, the same type of sensors are not interchangeable, seriously affecting the effects of using, to add to the difficulty, maintenance, debugging, some manufacturers has made efforts in this regard, (
But the interchangeability is still very poor)
Good results have been achieved.
5, humidity correction calibration is much more difficult than the correction of temperature.
Often with a standard thermometer for temperature calibration, calibration standard is difficult to achieve, and humidity dry wet bulb and some common pointer hygrometer can't be used as a calibration, accuracy cannot be guaranteed, because of its environmental conditions are very strict, in general,
* but humidity environment suitable for the conditions)
In the absence of a perfect test equipment, usually with simple saturated salt solution verification method, * * pot with digital display temperature measuring the temperature.
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