Humidity measurement Devices |Humidity , Relative and Specific humidity| Hygrometer

By | February 4, 2019

Humidity measurement Devices | Definition of Humidity , Relative humidity, and Specific humidity | Hygrometer | Hair hygrometer

1) Define humidity.
2) Define Relative humidity.
3) Define specific humidity.
4) What is hygrometer?
5) What is Hair hygrometer ?
6) Explain Hygrometer and their type Hair hygrometer.

Hi guys, here we learn definition of humidity, Definition of Relative humidity, Defination of specific humidity, Humidity measuring devices, Pyrometer, hair pyrometer, and lots of. So without wasting time now we learn.

Definition of humidity :

Humidity is a measure of the relative amount of water vapour present in the air or a gas. The most common units are grams per cubic meter (gma).

Definition of Relative humidity :

Relative humidity is the percentage of water vapour by weight present in a given volume of air or gas compared to the weight of water vapour present in the same volume of air or gas saturated with water’ vapour, at the same temperature and pressure, i.e., Relative humidity.

Definition of Specific humidity :

Specific humidity measures the weight of water vapour per unit weight of air. It’s unit is grams of water vapour per kilogram of air (g/kg).

Humidity Measuring devices :

Hygrometers :

1) Devices that indirectly measure humidity by sensing changes physical or electrical properties in materials due to their moisture content are called hygrometers.
2) Materials such as hair, skin, membranes, and thin strips of wood change their length as they absorb water. The change in length is humidity. directly related to the Such devices are used to measure relative humidity from 20 to 90 percent, with ac curacies of AL percent. Their operating temp. range is limited to less than ’70°C.’

Hair hygrometer :

1) Hair hygrometer is the simplest and oldest type of hygrometer.
2) It is made using hair as shown in Fig.
3) Human hair lengthens by 3 percent when the humidity changes from 0 to 100 percent, this property of hair can be used to operate a pointer or recording pen through a system of mechanical linkage.
4) The transducer element consists of strands of hair which are generally arranged parallel to each other.
5) It is not a precision instrument and not recommended where high degree of accuracy is required.
6) The change in length can be used to control a pointer far visual readings or a transducer such as linear variable differential transformers (LVDT) for an electrical output.

7) The hair hygrometer as an accuracy of about 5 percent for the humidity range 20 to 90 percent over the temperature range 5°C to 40°C.

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