Choose a vacuum gauge around the pressure you need to measure, the process gas and what you will do with the reading. A clear dial for an industrial vacuum line, a Pirani transducer and a high-vacuum instrument solve different measurement problems.
Start with absolute or relative pressure
A relative vacuum gauge measures against local atmospheric pressure. An absolute gauge measures pressure against a vacuum reference. State which one your process specification uses: a reading close to −1 bar on a general-purpose dial does not resolve the residual pressure needed for high-vacuum work.
If you are replacing an instrument, send a photograph of the full dial or display as well as the model label. Include units, measuring range and the pressure at which you normally operate.
Which vacuum gauge technology fits the job?
| Measurement need | Starting point | Selection checks |
|---|---|---|
| Local indication on an industrial vacuum line | Industrial vacuum dial gauges | Relative-pressure scale, readability, process gas, connection and vibration. Liquid-filled versions can help where vibration affects the pointer. |
| A mechanical absolute-pressure reading | Absolute capsule gauges | The specific pressure range and wetted-material compatibility. “Chemical-resistant” does not mean suitable for every chemical. |
| Electronic vacuum measurement through a suitable rough/medium-vacuum range | Pirani vacuum transducers | Gas-dependent response, measuring range, contamination, output and supply. |
| Measurement extending into high vacuum | Cold cathode / Pirani combination gauges | Working range, gas correction, installation and controller compatibility. |
| Measurement extending into ultra-high vacuum | Hot cathode / Pirani combination gauges | Model-specific range, filament protection, allowable conditions and connection. |
| Portable checks or a recorded pressure history | Portable vacuum meters and data loggers | Sensor principle, logging capability, range and connection for the selected version. |
A digital display does not tell you the measuring principle
Check the sensor behind the display. Pirani and ionisation instruments have gas-dependent responses, so the calibration gas and the gas in your process matter. An analogue output also needs the correct scaling: a matching connector does not establish electrical or measurement compatibility.
Compare analogue transducers and controllers as a measuring chain. Include the cable and display or control input when discussing a replacement.
Build the calibration requirement into the enquiry
Specify the test points that matter to your operation, rather than requesting a certificate without a range. Tell us whether you need an instrument-only calibration or a check of the sensor, cable and controller together. Include any acceptance tolerance or uncertainty requirement from your own process specification.
Girovac provides a vacuum gauge calibration service with the scope and certificate option confirmed for the instrument and test points. If an accredited certificate is required, say so at enquiry stage; coverage must be checked for the requested measurement. Calibration records the instrument’s performance under stated conditions and does not necessarily include adjustment or repair.
Match measurement to the vacuum installation
For a central industrial vacuum system, consider both local indication and the signal used for regulation. On a SIRELLA dry claw installation, select the gauge for the actual operating pressure; the instrument’s lower range does not extend the pump’s permitted duty.
For turbomolecular pump systems, discuss measurement of the chamber and backing line separately. They may require different instruments. The gauge and control arrangements must suit the pump and process instructions.
Vacuum gauge selection questions
Can I use a −1 to 0 bar dial for high vacuum?
A general-purpose relative-pressure dial cannot resolve the very low absolute pressures used in high-vacuum work. Compare the high-vacuum instruments against your required pressure range instead.
Can I replace a sensor with one that has the same thread?
Check the measurement principle, range, gas compatibility, output, supply and controller scaling as well as the thread or flange. Send both model references when asking about a replacement.
How often should a vacuum gauge be calibrated?
The interval depends on use, environment, measurement importance and previous calibration results. Share your existing interval and certificates with our calibration service so the requested work can be scoped. There is no single interval suitable for every vacuum gauge.
Can you quote a pump and its measurement equipment together?
Yes. Add the relevant pump, gauge and accessories to your quote shortlist, and tell us which items must work together. We will check the proposed configuration before quoting.
Get the instrument specification right
Send the pressure range and reference, process gas, connection, output or controller, quantity and certificate requirement. A model label or existing certificate is useful for replacement work.
Selection guidance reviewed September 2026 against the product information in the Girovac vacuum instrumentation catalogue. The linked product pages describe available instrument families; confirm the exact configuration, range and compatibility when ordering.
Laboratory vacuum selection · Gauges for composite vacuum · Vacuum holding and switching