Pressure measurement is the analysis of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area.
It plays an important part in the manufacturing process; therefore, a suitable pressure sensor is crucial to obtain accurate and quality data. Here are some important factors to consider when selecting the pressure sensor that best fit your process:
- Pressure Transmitter: measures the same force being applied but offers a common process signal as a representation for the pressure. A pressure transmitter is used for continuous pressure measurement but can possibly offer a visual display.
- Pressure Switch: measures the amount of force being applied and offers an electrical signal along with other variations, when certain conditions are met. These conditions can be pre-determined. Example: an alarm system or a shutdown valve
- Pressure Gauge: measures the amount of force being applied, but instead of an output, a visual representation of the pressure is given. Most pressure gauges use a needle on the face of a dial to indicate pressure, however digital representation can also be used.
- Gauge Pressure: The pressure which is measured above atmospheric pressure. Examples of industrial applications: open tank level, line pressure, blanket pressure in a tank
- Absolute Pressure: The pressure which is measured above vacuum. Examples of industrial applications: open tank level, line pressure, blanket pressure in a wet/dry tank, plant atmospheric reference
- Differential Pressure: Difference between two applied pressures points. Example of industrial applications: closed tank level, density, filter health, DP flow
In some cases, a pressure sensor may come into contact with a variety of chemicals, liquids or gases, or have to function in extremely harsh environments. Additional features and components like a diaphragm or housing maybe required to withstand extreme conditions. Example:
- Diaphragm seals are used to protect sensors from the process medium
- Pressure sensors for use with corrosive medium often feature housings made from stainless steel or plastics such as PVDF, PVC or PPS.
- Pressure sensors that features “flameproof enclosure” are designed specifically for hazardous environments with flammable materials or dust.
If an output signal is required, it is important to consider the electrical signal needed, ie 0-10V, 0.5-4.5V, 4-20mA, as well as AC and DC switch signals.
