Pressure gauges are the most common instruments in any process plant, yet they are often selected on habit rather than engineering. A gauge chosen on the wrong range, material or accuracy class will read inaccurately, fail early — or, in the worst case, create a safety hazard. This guide walks through the selection criteria in the order that matters.
1. Select the Measuring Range Correctly
The operating pressure should sit in the middle third of the scale (approximately 25–75 % of the full scale). Per EN 837-1, this is where a gauge delivers its best accuracy and longest service life:
- Too low a range — the pointer saturates at full scale, the gauge reads inaccurately and the mechanism wears out.
- Too high a range — the operating point sits at the bottom of the scale, where accuracy is worst; pressure fluctuations become hard to read.
- Rule of thumb: for a steady working pressure of 6 bar, choose a 0–10 bar gauge — not 0–6, not 0–16.
- For pulsating loads, use a range of 0–1.5× the max operating pressure, or fit a damped or liquid-filled version.
2. Choose the Accuracy Class
Accuracy classes follow EN 837-1: Class 2.5 (low cost, general indication), Class 1.6 (standard industrial), Class 1.0 (process quality), and higher-grade classes for calibration duties:
- Class 2.5 — general indication on pumps, compressors, hydraulic systems
- Class 1.6 — the standard for most industrial applications
- Class 1.0 — process plants, quality-critical readings, test benches
- Remember: accuracy is expressed as a percentage of full scale, so a Class 1.6 gauge on a 0–100 bar scale is accurate to ±1.6 bar anywhere on the scale.
3. Match the Wetted Materials to the Media
The wetted parts (Bourdon tube, socket, diaphragm) must be compatible with the measured medium. The two main families:
- Copper alloy internals — for air, water, oil, hydraulic fluids and non-aggressive gases. Typical of standard industrial gauges such as the WIKA 111.11.
- Stainless steel internals — for aggressive, corrosive or high-purity media (acids, caustics, food, pharmaceuticals). See the WIKA 232.30/233.30 range for process service.
If the medium is unknown or variable, stainless steel is the safer default. For media that crystallise, clog or are highly corrosive, consider a diaphragm seal to isolate the gauge.
4. Pick the Case Size and Mounting
Dial sizes follow the EN 837 series: 40, 50, 63, 80, 100 and 160 mm.
- 40–63 mm — panel-mounted on machines and control cabinets; compact gauges on hydraulic systems
- 80–100 mm — the standard for process and industrial readouts; most readable for operators
- 160 mm — control rooms and calibration where legibility is critical
Mounting options: radial (connection at the back, gauge faces forward) or axial (connection at the rear, gauge mounted on a panel), plus flush/panel mounting with clamping rings for control cabinets.
5. Check the Process Connection
The most common thread forms are G¼, G½ (per EN 837-1), ¼" and ½" NPT, and M20×1.5. Match the existing fitting — and remember that a new connection is not just a thread: the position (radial vs axial) and the torque matter for both sealing and accuracy. For high-vibration connections, a pressure snubber or damping element protects the gauge mechanism.
6. Decide on Liquid Filling
Liquid-filled gauges (glycerine or silicone oil) damp vibration and pulsation and extend service life on pumps, compressors and mobile equipment:
- Glycerine filling — standard for machine vibration damping (operating range roughly −20 °C to +60 °C)
- Silicone oil filling — where higher temperatures or food-grade service rules out glycerine
- If the process has strong vibration or pulsation, always choose the liquid-filled version rather than a dry gauge.
7. Consider Accessories Before You Mount
- Pressure snubber / pulsation damper — protects the gauge from pressure spikes
- Siphon tube — for steam service, condenses steam to protect the Bourdon tube from temperature
- Diaphragm seal — isolates the gauge from corrosive or clogging media
- Manifold / valve — allows isolation and zeroing without removing the gauge
8. Verify Standards and Certifications
For CE-marked installations the gauge should comply with EN 837-1 (Bourdon tube gauges) and, where pressurised equipment is involved, the Pressure Equipment Directive 2014/68/EU (PED). For hazardous areas, check ATEX/IECEx ratings. Ask for the datasheet — a reputable supplier provides it without hesitation.
Buying Guide for Glorient Customers
Glorient supplies genuine WIKA pressure gauges — from standard industrial models to stainless steel process gauges — with competitive pricing and worldwide delivery. To order correctly:
- Confirm your measuring range, process connection and medium compatibility (or send a photo of your old gauge's nameplate).
- Browse the pressure measurement range for the series you need — e.g. the 111.11 standard industrial gauge or the 232.30 stainless steel process gauge.
- Send your application details via the quote request form — we will confirm the exact model, accuracy class and accessories within 24 hours.
Pressure measurement is about matching range, material and accuracy to the process — not just picking a dial size. If you are unsure, send us your medium, working pressure and connection thread, and we will recommend the right gauge.
Frequently Asked Questions
What is the difference between a Bourdon-tube and a diaphragm pressure gauge?
A Bourdon-tube gauge uses a curved tube that straightens under pressure and is the standard for most gas and liquid applications. A diaphragm gauge uses a flexible membrane and is preferred for low pressures, viscous or clogging media, and where a chemical seal is needed.
What accuracy class do I need - 1.0, 1.6 or 2.5?
The class is the percentage error of the full-scale span. Class 1.0 (±1%) suits process control and calibration; 1.6 is the general industrial standard; 2.5 is adequate for simple indication. Match the class to the application - a precision test rig demands a finer class than a utility line.
How do I choose the correct pressure range?
Select a range where the normal operating pressure sits between roughly 25% and 75% of full scale, so the gauge reads in its most accurate and least-stressed zone. The maximum pressure must stay below the gauge full scale, with the overload rating providing the safety margin.