How to Choose an Industrial Pressure Gauge

Pick a pressure gauge by six things: dial size, range, accuracy class, process connection (thread), case fill and mounting. Get those six right and the gauge reads true, fits the port and survives the application. Get one wrong and you either cannot read it, cannot fit it, or wear it out early.

This is a short, ordered guide to each of the six, with the spec language you will see on the part. Our in-stock range runs from a 63 mm digital gauge up to a 160 mm test gauge, so most of the choices below map onto a real part you can order.

1. Dial size

Dial size is the diameter of the gauge face, given in millimetres. Common sizes are 63 mm, 100 mm, 125 mm and 160 mm.

63 mm: panel and machine mounting where space is tight, or close-range reading.
100 mm: the general-purpose default for workshop and plant use, readable at arm’s length.
125 mm and 160 mm: larger faces for fine reading or for test and calibration work, where you need to resolve small divisions.

Bigger dials are easier to read and usually carry finer graduations. Smaller dials fit panels and save space.

2. Range

Set the range so your normal working pressure sits between a quarter and three quarters of full scale. A gauge run near its top end all day wears the movement and loses accuracy.

Ranges are given in MPa, bar, kPa or psi depending on the gauge. Our general-purpose 100 mm gauge covers 0 to 160 MPa; the process and test gauges run to 0 to 250 MPa and 0 to 100 MPa. For a system that normally sits at, say, 80 MPa, a 0 to 160 MPa gauge keeps the needle in the safe middle band.

If the system can spike or pulse, leave more headroom and consider a liquid-filled case (below).

3. Accuracy class

Accuracy is quoted as a percentage of full scale (F.S.). Lower is tighter.

1.0% to 1.6% F.S.: general workshop and plant gauges. Fine for monitoring.
0.3% F.S.: test gauges, for checking and setting other equipment.
0.05% F.S.: precision and reference work, where the gauge is the standard.

On a 100 MPa gauge, 1.0% F.S. means the reading is within 1 MPa across the scale; 0.3% F.S. tightens that to 0.3 MPa. Buy the accuracy the job needs, not the tightest available, because higher classes cost more and are easier to knock out of calibration.

4. Process connection (thread)

The thread has to match the port you are screwing into. The two common standards are BSP (British Standard Pipe, the usual fitment in South Africa) and NPT (National Pipe Taper, common on imported equipment). They are not interchangeable, and forcing the wrong one damages both parts.

Check the size as well as the standard: 1/8”, 1/4” and 1/2” are all common. Our gauges ship in 1/4” BSP, 1/2” BSP and 1/2” NPT depending on the model, so confirm the port before you order.

5. Case fill (dry or liquid-filled)

A dry gauge is fine for steady pressure. A liquid-filled gauge (usually glycerine) damps the needle, so it reads cleanly under vibration or rapid pulsing, and the fluid protects the movement.

Choose liquid-filled for pumps, compressors, hydraulics and anything mounted on machinery that shakes. Choose dry for static lines and for test gauges, where you want no damping between you and the true reading.

6. Mounting

Mounting covers where the connection enters and how the gauge is held:

Bottom entry: the standard, connection at six o’clock, gauge sits on the line.
Back (rear) entry: connection behind the dial, for flush panel mounting.
Bayonet or surface mount: for panels and enclosures, often with a front bezel.

Match the mounting to the panel or bracket you are fitting into, not the other way around.

Selection checklist

Before you order, confirm:

Dial size fits the space and reads at your working distance.
Working pressure sits in the middle half of the range.
Accuracy class matches the job (monitor, test or reference).
Thread standard and size match the port (BSP vs NPT, and the size).
Case fill suits the application (liquid-filled for vibration and pulsing).
Mounting matches the bracket or panel.

How to order or request a quote

Send us the six specs above, or the part number off the gauge you are replacing, and we will confirm stock, price and lead time. If you are unsure on range or thread, send a photo of the old gauge and the port, and we will match it.

Browse the full range on the Pressure Gauges page, or request a quote with your list.