Table of Contents
Type of pressure:- There are multiple ways in which pressure can be describe. To accurately identify and relay pressure measurements, the application must be considered. Pressure sensors use the following type of pressure-
Probably the most important pressure for life on Earth is atmospheric pressure, Pmb (amb = ambien = surroundings). It is formed by the weight of the atmosphere which surrounds the earth almost to the height 500 km. Up to this height, at which absolute pressure Pabs = zero, its magnitude decreases continuously. In addition, atmospheric pressure is subject to weather-dependent fluctuations, as is only well known from daily weather reports. At sea level, the Pemb‘s average is 1013.25 hectopascals (hPa), which corresponds to 1013.25 millibars (mbar). With “cyclone” and “anticyclone“, this pressure varies by about 5%.
The most obvious reference pressure is the pressure zero (vacuum), which exists in the air-free space of the universe. The pressure relative to this reference pressure is known as the absolute pressure. Thus, with absolute pressure, it is always measured that there is a difference of ideal vacuum. This means that ambient pressure, and thus external influences such as weather or altitude above sea level, do not affect the pressure measurement. For essential distinction from other types of pressure, it is denoted with the index “Abs”, derived from the Latin “absolutus”, meaning separate, independent.
Gauge pressure (relative pressure)
The pressure most often measured in the technical field is the atmospheric pressure difference, Pe (E = greater = greater). This is the difference between an absolute pressure, Pabs and the relevant (absolute) atmospheric pressure (Pe = Pabs – Pamb) and is known, for short, as gauge pressure. Since the gauge pressure does not measure the vacuum difference, but rather for the current ambient pressure (atmospheric pressure), the pressure measurement changes due to external influences such as weather or altitude above sea level. If a gauge pressure sensor is used by mistake in an application where the absolute pressure is actually measured, one may encounter additional errors of +/- 30 mbar due to weather changes and 200 mbar in the case of a change in location. should be considered with measurement errors of up to 2000 m above sea level.
The reference point of each pressure is clearly defined by the indexes of the formula symbols “abs,” “amb,” and “e.” They are only associated with the formula letter p, not unit symbols.
The difference between the two pressures, p1 and p2, is known as the pressure difference, p = p1 – p2. In cases where the difference between the two pressures only represents the measured variable, a difference refers to the pressure, p1.2.
Accordingly, to measure differential pressure, first two different pressures are captured in the measuring instrument (such as differential pressure gauge or differential pressure sensor). Only if the measured values differ from each other, the differential pressure will be indicated. In cases where differential pressure measurement is required, for example, filter monitoring and level measurement in closed vessels.