Hygrometer Therma-Hygrometer with...
The new range of ETI pressure meters is designed for use in measuring non-corrosive gauge or differential air or gas pressure in a wide range of industries.
● flue draught measurement
● gas pressure in heating appliances
● air conditioning ducts
● monitoring of filter differential pressure
● velocity measurement with a pitot tube
absolute, gauge or differential pressure
If serious errors are to be avoided, it is important when taking pressure measurements to be clear which mode of measurement is to be used: absolute, gauge or differential.
If a vessel were to contain no molecules whatsoever, the pressure would be zero. Pressure measured on a scale which uses this zero value as its reference point is said to
be absolute pressure.
In everyday life, however, many applications of pressure are not so dependent on the absolute pressure value, but the difference between the absolute and the pressure of the
atmosphere. For example, a punctured tyre with no air in it would read 'zero' on a tyre pressure gauge, even though still containing atmospheric air. Such gauges are designed
to measure pressure values that are expressed with respect to atmospheric pressure and thus indicate zero when the measurement port 'merely' contains molecules at atmospheric pressure. These measurements are known as gauge pressure measurements. Thus the difference between an absolute pressure value and a gauge pressure value is the variable value of the atmospheric pressure.
In other applications, where knowledge of the pressure difference between two places or systems is needed, the reference pressure may not necessarily be either zero or the atmospheric pressure but some other value. These are known as differential pressures. For example, the flow of gas along a pipeline depends on the pressure difference between the ends of the pipe and, in practice, both ends are usually at comparatively high pressures.
A manometer is a pressure measuring instrument that measures low pressure and is used, primarily, for measuring gas pressure or low atmospheric pressure and normally measures in mbar.
A pressure meter is a pressure measuring instrument that measures high pressure, non-corrosive air or gas and normally measures in psi (pounds per square inch).