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Pressure sensor selection starts with the pressure you need to measure, not the largest number on a catalogue page. A pump outlet, a vacuum vessel and a filter can all need pressure information while requiring different reference types, process connections and overpressure checks.
Specify the complete instrument rather than a bare sensing element when the job requires a process connection, electrical enclosure and conditioned output. This guide compares selection requirements; it does not assign generic industrial specifications to a METRAVON pressure-transmitter series.
Pressure sensor selection begins with the reference
| Reference | Question the measurement answers |
|---|---|
| Gauge | How far is the process pressure above or below the local atmospheric reference? |
| Absolute | What is the process pressure relative to vacuum, regardless of atmospheric changes? |
| Differential | What is the pressure difference between the two specified process points? |
| Sealed gauge | Is a fixed sealed reference appropriate, and what effect will atmospheric variation have on the required result? |
Do not leave "vacuum sensor" as the complete pressure definition. State whether the requested reading is absolute pressure or negative gauge pressure. For a filter, specify the differential span and the pressure that may be present on both ports. A small differential range does not establish the maximum permitted line pressure.
For hydrostatic level, pressure is only the first part of the calculation. Liquid density, sensor elevation and any gas-space pressure affect the inferred level. Do not select a single-port gauge transmitter for a sealed tank on the assumption that all measured pressure comes from liquid depth.
Separate measurement range from survival limits
List the normal operating interval, maximum sustained pressure and credible startup or shutdown peaks. Ask how the specified overload limit is defined, including any duration, cycling or temperature conditions. Burst pressure is not an acceptable operating allowance.
A larger range may accommodate the process better, but its effect on measurement error depends on the accuracy specification. Consider this arithmetic example, not a product rating: an error of 0.25% of a 10 bar span is 0.025 bar; the same percentage of a 100 bar span is 0.25 bar. At a 2 bar reading, those absolute errors have very different significance.
Compare errors on the same basis. A percentage of span, a percentage of reading and a total error band are not interchangeable. Identify whether temperature effects, long-term drift and installation effects are included or separate. Evaluate the error in the units used by the process decision, not just the catalogue percentage.
Inspect the wetted connection as a small process assembly
The diaphragm is not the only wetted part. Include the pressure port, seal and any isolation fitting when checking chemical compatibility at the actual concentration and temperature. A corrosion-resistant housing does not establish compatibility of the internal seal.
For sticky or crystallising media, review whether a narrow passage can block. A flush diaphragm or a suitable remote-seal arrangement may address that geometry, but each has installation and temperature effects of its own. Do not specify a flush diaphragm as a universal remedy for all slurry, abrasion or cleaning duties.
Steam service requires assessment of how process heat reaches the instrument. Any cooling, condensate or remote-seal arrangement must match the process design and selected equipment. Distinguish the medium temperature from the ambient limit of the electronics. A transmitter with an adequate pressure range can still be unsuitable thermally.
Order the interface that the receiving system can use
For a two-wire 4-20 mA transmitter, verify the available voltage at the instrument after cable, input and barrier drops. For a voltage output, confirm the supply, signal reference and receiving-input range. RS485 describes an electrical interface; specify Modbus RTU only when the exact device supports it, together with the register and scaling information.
Decide whether maintenance needs a local display, diagnostic access or remote configuration. These requirements affect the supplied configuration and commissioning work. A price comparison should separate the transmitter, mating connector, process adaptor, cable and any necessary isolation or signal-conditioning components.
Q1. Should every range be a fixed multiple of normal pressure?
No. A multiplier cannot replace the operating envelope, transient information and required error at the working pressure. Review the candidate's measuring and overload limits separately, particularly on pump and hydraulic circuits.
Q2. Is a load cell a pressure sensor?
A load cell measures force through a mechanical load path. Fluid pressure measurement needs a defined pressure-sensitive interface and calibration. Similar strain-sensing principles do not make a tension/compression load cell a pipeline pressure transmitter.
Q3. What makes a quotation ready for technical comparison?
It identifies the pressure reference, configured span, operating and peak pressures, wetted materials, connection, output and temperature conditions. The offered document should state its error basis and exact configuration. A family brochure without those selections is not yet a complete technical offer.
Summary
Define the pressure reference and process envelope, then compare the connection, measurement error and receiving interface. Send METRAVON the measuring-point specification and existing nameplate, if available. Request confirmation of a suitable model before ordering; neither supply availability nor certification follows from this general comparison. For an existing fault, use the pressure transmitter troubleshooting guide.
