Humidity sensor: what is it?

the sensor allows, as its name suggests, to measure the ambient humidity. A useful measure in matter of meteorology, but also in the housing sector. Indeed, thehumidity in a house can cause problems. A air too wet, or too dry, can be a source of inconvenience, even cause sanitary risks.

Capacitive and resistive humidity sensors

There are humidity sensors (or hygrometers) capacitive and resistive humidity probes (or hygrometers).

A capacitive probe plays on the sensitivity to the relative humidity of the ambient air from the constant dielectric of materials such asalumina — or thealuminum oxide — or sometimes polymers. At the heart of the system therefore, a capacitor whose capacity varies according to humidity. The sensitivity of this type of instrument is around 3% and its measurement range is wide.

A resistive sensor, meanwhile, plays on the humidity sensitivity of the resistivity of certain materials, the chloride of lithium for example. The latter has, in fact, a high resistance when it is dry and a low resistance when it is wet. The problem is that this type of probe only works on a reduced humidity range. Pay attention also to the resistances of materials which can vary in parallel with the temperature.