There are three basic types of humidity sensors: capacitive, resistive, and thermal. All three types of sensors monitor small changes in the atmosphere to calculate the humidity in the air. Let's take a look at these types in detail.

Capacitive humidity sensor: Capacitive humidity sensor measures relative humidity by placing a thin metal oxide strip between two electrodes. The capacitive humidity sensor is linear, can measure 0% to 100% relative humidity, is the only full range of relative humidity measurement equipment. The cryogenic effect allows them to be used over a wide temperature range without active temperature compensation. Therefore, capacitive humidity sensor plays a dominant role in atmospheric and process measurement and is mainly used in meteorological, commercial, and industrial fields. However, the circuit of the capacitive humidity sensor is complex, so it needs to be calibrated regularly.

Resistant humidity sensor: a resistive humidity sensor uses ions in salt to measure the electrical impedance of atoms. With the change of humidity, the resistance of the electrodes on both sides of the salt medium will also change.

Thermal and Humidity Sensors: Two thermal sensors conduct electricity according to the humidity of the surrounding air. One sensor is enclosed in dry nitrogen, while the other measures ambient air. The difference between the two can be measured by humidity.

Yokogawa	Bently Nevada	Siemens
SPW482-13	128275-01	39PSMNAN
SPW481-13	128275-01F 130944-01	39PSR4ANDN 16114-200/01
SNT511-13	128276-01E 131151-01	39RTMCAN
SNT501-13	129478-01	39SDM024DCCBN
SNT411-13	131178-01	39VIMCBN
SNT401-13	133300-01	39VIMCCN
SNT10D	133323-01	39VIMNBN
SNB10D	133396-01	3RX9306-1AA00
SED4D-11	133442-01	3TE4602-5A
SED4D-01	133819-02	405-15ABM
SED2D-11	134652-01	405-4DAC-1
SED2D-01	135137-01	405-4DAC-2
SEC401-11	135145-01	405-8ADC-1
SEA4D-11	135489-01	424K1105
SEA4D-01	135813-01	500-2151
SDV541-S33	136188-01	505-4232 505-4232A
SDV541-S23	136188-02	505-4332
SDV531-S33	136711-02	505-4532
SDV531-S23 S1	136719-01	505-4632
SDV531-S13	140471-01	505-4732