Analogue Pressure Gauges: Types, Accuracy, Uses and How to Choose

Quick answer: an analogue pressure gauge (also spelled analog) shows pressure with a pointer moving across a printed dial, with no battery or electronics. The most common type is the Bourdon tube gauge. Analogue gauges are simple, robust and inexpensive, and they suit permanent fittings on pumps, compressors, boilers and hydraulic lines. Their accuracy is stated as a class, usually between 0.6% and 2.5% of full scale for industrial models. Choose one by range, size, material, fill, connection and accuracy. This guide explains how analogue gauges work, how they compare with digital ones, how to pick the right one from our range, and how to keep it reliable.

What is an analogue pressure gauge?

Analogue means the reading is shown by a continuous physical movement, here a pointer, rather than as digits. Inside most analogue gauges is a curved metal tube sealed at one end. Pressure inside tries to straighten the tube. The free end moves a small distance, and a link and a geared sector turn that movement into the rotation of the pointer. When pressure falls, the tube springs back and the pointer returns to zero. For the full mechanism, see Bourdon tube pressure gauges explained.

Other analogue designs include capsule gauges for very low pressure and diaphragm gauges for aggressive media. All of them show pressure on a dial and need no power.

Why people still choose analogue gauges

• No power needed: they work in remote places and during power failures.
• Quick to read: an operator can see at a glance whether the pointer is in the normal band, and a trend is easy to spot.
• Rugged: they tolerate heat, cold, dust and rough handling better than most electronics.
• Cost effective: for general indication they cost much less than a digital gauge of similar range.
• Safe in hazardous places: a purely mechanical gauge has no electrical ignition source, although suitability for a zone still depends on its construction and certification.

Where analogue gauges fall short

• Accuracy is usually lower than that of precision digital gauges.
• Reading depends on the observer, because of parallax and the fineness of the scale.
• They cannot log data or switch units, though many have a dual scale.
• Vibration and pulsation can damage a dry gauge, which is why liquid filled models exist.

For a head-to-head comparison with real models, read analogue vs digital pressure gauges compared.

Analogue gauge accuracy

Under EN 837-1, accuracy classes include 0.6, 1.0, 1.6, 2.5 and 4.0, where the number is the permitted error as a percentage of the span. The gauges in our range show typical values.

To see what these percentages mean in real units, read pressure gauge accuracy compared in real numbers.

How to choose an analogue gauge: seven steps

1. Range. Divide the normal working pressure by 0.75 for a steady load (0.66 if it pulsates) and round up to the next standard range. See the range selection guide.
2. Size. 63 mm for compact panels, 100 mm for standard industrial use, 150 to 160 mm where reading from a distance matters.
3. Material. Brass and copper alloy suit air, water and oil. Use stainless steel for corrosive media, food areas and coastal sites.
4. Fill. Choose a liquid filled gauge where there is vibration or pulsation. See liquid filled vs dry.
5. Connection. Match thread type, size and position. See connection types and thread sizes.
6. Accuracy. Pick the class that matches the risk of a wrong reading.
7. Safety features. Consider safety glass, a solid front and a blowout back for high pressure or hazardous duty.

Analogue gauges by application

Reading an analogue gauge accurately

1. Look at the dial from directly in front to avoid parallax.
2. Identify the unit and whether there is a second scale. Many of our gauges show kPa in black and psi in red.
3. Work out what one small division represents before reading.
4. Estimate between marks only if the scale allows it. Reading to a fraction of a division is not meaningful beyond the gauge’s accuracy.
5. Check that the pointer returns to zero when the gauge is vented.

Example. A 0 to 1,000 kPa dial has marks every 20 kPa and a class 1.6 accuracy. The permitted error is 16 kPa. Reading the pointer to the nearest 5 kPa gives no extra information, because the gauge itself may be 16 kPa out.

Installation and care

• Fit an isolation valve so the gauge can be removed safely.
• Tighten using a spanner on the socket flats, never the case.
• Use a snubber on pulsating lines and a pigtail on hot ones.
• Do not exceed the range, even briefly.
• Check for a bent pointer, cracked window, leaks or a pointer that rests away from zero, and replace the gauge if you find one.
• Have gauges checked against a reference at a regular interval. See pressure gauge calibration.

Dial layout and sizes at a glance

Typical failure modes

A copy-and-paste specification

When you order or write a tender, state each of these so every supplier quotes the same thing: gauge type (Bourdon, capsule or diaphragm); dial size; range and units; accuracy class; case and wetted materials; dry or liquid filled; connection thread, size and position; window type; over-range or blowout features; temperature at the gauge; media; and the standard (EN 837-1, AS 1349 or equivalent). A one-paragraph specification prevents most ordering mistakes.

Standards you will meet

• EN 837-1: European standard for Bourdon tube gauges.
• AS 1349: Australian standard for Bourdon tube pressure and vacuum gauges.
• ASME B40.100: American standard for pressure gauges.

Your site or contract may name one. Confirm before you order.

Liquid fill options in brief

Glycerine is the usual fill for general industrial duty and damps vibration well. Silicone oil suits wider temperature ranges and colder sites. Some applications must not be liquid filled at all, such as oxygen service, where gauges have to be cleaned and kept oil free. Always check the maker’s temperature limits for the fill. See liquid filled vs dry pressure gauges.

Worked example: sizing a gauge for a 10 bar compressor

The compressor cuts out at 10 bar and shakes the pipework. Divide 10 by 0.75 to get 13.3 bar, then round up to the next standard range, 0 to 16 bar. A 100 mm liquid filled gauge in class 2.5 can be wrong by 0.4 bar at any point, which is fine for indication. If the same gauge were used to set a regulator for a tool that needs 6 bar plus or minus 0.2 bar, class 2.5 would not be good enough, and a digital gauge or a class 1.0 test gauge would be the right tool. The range, the fill and the class each answer a different question.

Common buying mistakes

• Choosing the range from the maximum pressure only, with no headroom.
• Ordering by dial size alone and finding the thread is wrong.
• Using a dry gauge on a vibrating pump and replacing it every few months.
• Expecting a class 2.5 gauge to verify a tight tolerance.
• Forgetting a pigtail on a steam line.

Frequently asked questions

Is analog the same as analogue?

Yes. Analog is the US spelling. Australian and British usage is analogue.

How accurate is an analogue pressure gauge?

Industrial gauges are typically 0.5% to 2.5% of full scale. Test gauges can be better.

Which is better, analogue or digital?

Neither in every case. Analogue suits permanent, rugged duty. Digital suits testing and records.

Do analogue gauges need calibration?

Yes. They drift with use, and a yearly check is a common starting interval.

Can I get a gauge in psi and kPa?

Many have a dual scale. Our stainless and liquid filled models show kPa and psi on the same dial.

Where to go next

Browse the pressure gauges category, read what is a pressure gauge, or see our pressure gauge supplier guide. For help, contact us.