Hygrometer & Humidity Meter Range
Hygrometer - A Hygrometer/Humidity Meter is used to measure the amount of water vapour in the air and is expressed as RH (Relative Humidity) %
We stock many types of Hygrometer which can be found below and a description of the way each type works at the bottom of this page.
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Hygrometer/Humidity Meter Facts:
- Used to measure the amount of water vapour in the air
- Expressed as RH (Relative Humidity) %
- 100% RH is fully saturated
- Optimum levels vary with the requirements of the process (fibres need high humidity while grain needs low humidity)
- A comfortable level for the human living environment is considered to be 45-65%
- Too dry affects the skin and respiration
- Too wet can cause rot and mildew
Types of Hygrometer/Humidity Meters in our range:
1. Uses a material such as paper or hair which reacts to moisture by expanding or contracting. When coiled and with one end linked to a pointer this movement is related to RH on an appropriately graduated dial scale.
2. Uses electrical signals which alter in relation to the presence of moisture. The two most common types of sensor are Capacitive and Resistive
Capacitive – a current is applied across two plates and the capacitance measured is related to the RH and is indicated on an electronic display
Resistive – measures the change in conductivity of a polymer membrane caused by moisture absorption which is related to the RH and is indicated on an electronic display
NB – our models are the Capacitive type
3. Uses the temperature difference between two adjacent glass thermometers when one is cooled by evaporation as a result of its bulb being encased in a wet wicking material. This is known as the wet bulb depression and when related to the dry bulb temperature indicates the RH. The two types are the Masons Hygrometer and the Whirling Hygrometer (also known as a Sling Psychrometer)
Masons Hygrometer – a static instrument that relies on natural air movement to cool the wet bulb. The RH is determined by relating the wet bulb depression to the dry bulb temperature on a table supplied.
Whirling Hygrometer – by encouraging airflow over the wet bulb (by rotating the thermometers) a quicker and more accurate reading is possible.
There are two models of the Whirling Hygrometer:
- Traditional (folding handle) – uses a table to determine RH
- Compact (enclosed housing) – uses an integral slide-rule mechanism to determine RH