Pressure measuring instruments: How to choose the right model
A pressure measuring instrument must suit the specific application. Before choosing an instrument, you should establish which medium you will be measuring, what type of pressure you need to measure, which pressure range is relevant, and whether you need a pressure transmitter, pressure switch or pressure gauge.
Start with the medium before choosing a pressure measuring instrument
The choice of pressure measuring instrument depends first and foremost on the medium to be measured. This could be air, a neutral gas, water, diesel or another liquid or gas. The medium determines the requirements for the instrument’s materials, as different materials offer different levels of resistance to gases and liquids.
The choice of materials therefore directly affects whether the pressure measuring instrument operates effectively and reliably in the application. An instrument designed for air or a neutral gas will not necessarily be the right solution for liquids, aggressive media or applications with specific requirements for hygiene, temperature or the process environment.
Establish the pressure type and pressure range
When choosing a pressure measuring instrument, you need to know both the pressure type and the pressure range. The pressure type could, for example, be gauge pressure, absolute pressure, differential pressure or vacuum. Many applications measure gauge pressure, but other pressure types may be required depending on the process.
The pressure range is just as important. Applications operating at 10 bar, 600 bar or 100 Pa require different types of pressure measuring instruments. The instrument must be able to withstand the load while measuring accurately within its intended operating range.
Should you choose a pressure transmitter, pressure switch or pressure gauge?
The output signal depends on how the pressure reading will be used in the application. If the pressure needs to be monitored continuously, a pressure transmitter with an analogue output signal is often a suitable choice. If you only need to know whether the pressure is above or below a certain level, a pressure switch with a digital on/off signal may be sufficient.
If the measurement only needs to be read visually, a pressure gauge may be the right solution. The choice is therefore not just about the pressure itself, but also about how the measurement will be used for control, monitoring or operation.
Questions to answer before choosing a pressure measuring instrument:
- Which medium will the pressure measuring instrument measure?
- Is the medium air, a neutral gas, water, diesel or something else?
- Do you need to measure gauge pressure, absolute pressure, differential pressure or vacuum?
- What pressure range does the solution need to measure within?
- Does the measurement need to be continuous?
- Do you need an analogue output signal, fieldbus or an on/off signal?
- Is a pressure transmitter, pressure switch or pressure gauge the best solution?
- What process connection do you need?
- Does the connection need an internal or external thread?
- Do you need a DIN-A connector, M12 connector, cable connection or another type of connector?
- Does the pressure measuring instrument need a flush diaphragm to prevent dirt from accumulating inside it?
Connection and installation can be crucial
The process connection and electrical connector are important details when ensuring that the pressure measuring instrument fits the specific installation. Among other things, you should establish the thread type and size, and whether the connection needs an internal or external thread.
In some applications, a flush diaphragm may be relevant because it can help prevent dirt from accumulating in the pressure measuring instrument. On the electrical side, you also need to choose the connector or cable connection that suits the rest of the installation, such as a DIN-A connector, M12 connector or direct cable connection.
Once the medium, pressure type, pressure range, output signal and connection have been established, you will be in a much better position to choose a pressure measuring instrument that works effectively in the application.
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