How does a pressure gauge work?
In analogue pressure gauges (in accordance with EN 837-1), process pressure acts on a Bourdon tube. As pressure increases, the tube deflects further. A rack-and-pinion mechanism translates this movement into a pointer position on the dial. This principle is proven, low-maintenance and requires no external power supply.
A digital pressure gauge works differently: a built-in pressure transducer – piezoresistive or capacitive – measures the deflection of a diaphragm and converts it into an electrical signal. A microprocessor processes the signal and displays the value on a digital screen. Some models feature a 4–20 mA or IO-Link output for integration into your PLC or SCADA system. If you also need continuous pressure measurement without local readout, take a look at our pressure transmitters and pressure sensors.
What does a pressure gauge measure?
Depending on the type, a pressure gauge measures:
- Gauge pressure – pressure relative to atmospheric pressure (most widely used)
- Absolute pressure – pressure relative to vacuum (vacuum pumps, vapour pressure measurements)
- Differential pressure – the pressure difference between two points, for example across a filter or heat exchanger
Differential pressure gauges are also used for flow measurement in combination with an orifice plate or pitot tube. You can find more information on our flowmeters page. For differential pressure gauges, Ebora supplies versions from Mid-west Instruments and Wika.
Analogue or digital pressure gauge – which type should you choose?
The choice depends on your application, environment and whether you need to log data.
| Situation |
Recommended type |
| Simple local readout, no power supply available |
Analogue pressure gauge (Bourdon) |
| High accuracy required (±0.1% or better) |
Digital pressure gauge |
| Data logging or remote monitoring required |
Digital pressure gauge with output |
| Shock- and vibration-prone environment |
Liquid-filled gauge (glycerine or silicone oil) |
| Hazardous area (ATEX) |
ATEX-certified pressure gauge |
| Aggressive media (acids, alkalis) |
Chemically resistant version (stainless steel, PTFE diaphragm) |
Pressure gauge for compressed air
A compressed air pressure gauge is used in compressed air systems, compressor installations and pneumatic drives. Common pressure ranges are 0–10 bar and 0–16 bar. If you choose a liquid-filled version, the fill fluid dampens the pressure fluctuations generated by compressors – significantly extending service life. Standard connection sizes are G1/4" and G1/2" male thread.
Note when selecting: choose a gauge with a measuring range at least 25% above your maximum working pressure. This prevents the pointer from consistently sitting in the upper quarter of the scale, which accelerates wear of the measuring mechanism.
Pressure gauge for water
For water pressure, heating installations and cooling water systems, different requirements apply compared to compressed air. The medium may contain limescale, corrosive substances or small particles. In that case, choose a gauge with a stainless steel measuring cell or a diaphragm seal that protects the instrument from the process medium. For drinking water installations, models are available that comply with drinking water contact requirements (KTW/W270). A glycerine-filled version is well suited for water applications. Ebora supplies hygienic pressure gauges for water pressure from Hengesbach, Wika and IFM.
Pressure gauge for steam
Steam applications have specific material requirements. Use only a pressure gauge filled with silicone oil — glycerine is not suitable for steam because the fill fluid can boil at high temperatures, damaging the instrument. Silicone oil withstands temperatures from -40°C to +150°C and remains stable under the pressure and temperature fluctuations typical of steam installations. Ebora supplies hygienic pressure gauges for steam applications from Hengesbach, Wika and IFM.
Liquid-filled gauges for vibration- and shock-prone environments
In environments with constant vibration or pressure spikes – compressor blow-off lines, pumps, hydraulic presses – we recommend liquid-filled pressure gauges. The internal fluid dampens movement of the measuring mechanism, reducing wear on the rack-and-pinion assembly and pointer shaft, stabilising readout and extending service life.
Silicone oil is suitable for temperatures from -40°C to +150°C and can be used in contact with oxygen. Glycerine is more economical, but is not suitable for temperatures below 0°C and must not be used in steam applications — at high steam temperatures, glycerine can boil, damaging the instrument.
ATEX pressure gauges for hazardous areas
In environments containing explosive gas or dust – chemical industry, offshore, food processing with alcohol vapours – measuring equipment must comply with the ATEX Directive (2014/34/EU). ATEX-certified pressure gauges are constructed with spark-free materials and meet the appropriate category classification for Zone 1, 2, 21 or 22. Further information on ATEX applications is available on our ATEX page.
Pressure gauge selection guide
Use the points below to quickly determine which type suits your situation:
- Compressed air, compressor, pneumatics – analogue Bourdon gauge, liquid-filled if needed
- Water, heating installations, cooling water – liquid-tight version, stainless steel measuring cell, glycerine fill suitable
- Steam – silicone oil-filled version, no glycerine
- Aggressive or corrosive media – chemically resistant version with diaphragm seal
- Data logging or PLC connection – digital gauge with 4–20 mA or IO-Link output
- Hazardous area – ATEX-certified pressure gauge
- Pressure difference across filter or heat exchanger – differential pressure gauge from Mid-west Instruments or Wika
Not sure about the right pressure range, connection size or material? Submit your question via our contact form or call our technical department directly.
Frequently asked questions
What is the difference between a gauge pressure and an absolute pressure gauge?
A gauge pressure instrument measures pressure relative to atmospheric pressure. An absolute pressure gauge measures relative to absolute vacuum. For most industrial applications, a gauge pressure instrument is sufficient. Absolute pressure gauges are used in vacuum pump applications and vapour pressure measurements.
How do I select the right pressure range?
Choose a measuring range where your working pressure falls in the middle third of the scale. A compressor operating at 10 bar requires a gauge with a 0–16 bar range. Consistently measuring in the upper quarter increases the risk of damage to the measuring mechanism.
When is a diaphragm seal required?
A diaphragm seal is fitted between the process medium and the pressure gauge when the medium is aggressive, viscous, crystallising or contaminated. The seal protects the instrument and extends its service life.
How often should a pressure gauge be calibrated?
For most industrial applications, a calibration interval of 12 months is standard. Critical processes – such as medical applications or safety-relevant processes – require a shorter cycle of 3 to 6 months.
Can a digital pressure gauge also be used as a switch?
Yes, various digital pressure gauges are available with integrated switching outputs (one or two setpoints). These allow you to directly control switches, alarm relays or valves when over- or underpressure occurs.
Select the right pressure gauge based on medium, pressure range, connection thread and environmental classification, or request technical advice directly via our contact form.
