Resistive Hygrometer vs Capacitive Hygrometer | Difference between Resistive Hygrometer and Capacitive Hygrometer

This page compares Resistive Hygrometer vs Capacitive Hygrometer and mentions difference between Resistive Hygrometer and Capacitive Hygrometer with respect to construction and working principle.

Relative Humidity measures water vapor relative to the temperature of the air as a percent. In other words, it is a measure of actual amount of water vapor in the air compare to the total amount of vapor which can exist in the air at its current temperature.

Following are the methods used for relative humidity measurement.
• Galvanometric Hygrometer
• Resistive Hygrometer
• Capacitive Hygrometer
• Microwave refractometer
• Aluminium Oxide Hygrometer
• Sling Psychrometer
• Crystal Hygrometer

Let us discuss Resistive Hygrometer and Capacitive Hygrometer methods.

Resistive Hygrometer

• This hygrometer type utilizes resistivity change with respect to humidity for relative humidity measurement. The figure-1 depicts Resistive Hygrometer.
• It uses hygrometric salt material such as LiCl (Lithium Chloride) for this purpose.
• Resistance of this material changes to wide range from 10⁴ to 10⁹ Ohms with humidity change from 100% to 0% respectively.
• Higher relative humidity will result into more moisture absorbtion by LiCl material. This will lower the resistance of the material and vice versa.

Capacitive Hygrometer

• This hygrometer type utilizes change in dielectric constant with respect to humidity for relative humidity measurement. The figure-2 depicts Capacitive Hygrometer.
• Some of the hygroscopic materials exhibit this property.
• This hygroscopic material is placed between two parallel plates of a capacitor in the Capacitive Hygrometer.
• The change in dielectric constant can be detected by capacitive transducer.

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