What to Consider When Calibrating Pressure Gauges



Modern pressure gauges offer increasingly accurate readings but they are still prone to losing their accuracy over time. This makes the regular calibration of pressure gauges a necessary and important task for maintaining the efficiency and safety of all your pressure-related processes. In this blog, GNW Instrumentation explains the benefits of calibrating your pressure gauges, citing common errors to look out for and calibration parameters to bear in mind and hopefully answer “What to consider when calibrating pressure gauges”


Do I Need To Calibrate My Pressure Gauges?

Your first thought when you might be wondering what to consider when calibrating pressure gauges might be, “Do they need calibrating?” The short answer is: yes! You do need to calibrate your pressure gauges. Pressure gauges lose their accuracy over time. So it is important to carry out a regular calibration of pressure gauges to ensure they perform optimally. At the very least, your pressure gauges should be calibrated annually. You might also wish to calibrate your pressure gauges before installations, as part of planned preventative maintenance, and during any ISO audits.

Three main types of pressure are typically measured. Absolute Pressure is the pressure relative to a complete vacuum. Gauge Pressure is the difference between an absolute pressure and the prevailing atmospheric pressure. Differential Pressure is the difference between any two applied pressures. Calibration laboratories either use dead-weight pressure gauge calibrators or digital pressure calibration instruments to measure these types of pressure.  

Types Of Errors In Pressure Gauges

There are three main errors in pressure gauges that should alert you to the need for calibration and should go a long way in helping you on what to consider when calibrating pressure gauges:

  • Zero-point error – This is when the start of the measuring range is either too high or too low (known as the zero offset). This will subsequently shift the entire scale up or down by the zero offset value.
  • Span error – This is when the distances between individual divisions (known as the span) from the zero point to the full-scale value are even but wrong. This can amplify errors at the upper end of the scale.
  • Non-linearity – This is when the distances between individual divisions from the zero point to the full-scale value are not even (or non-linear). This turns the ideal straight line into a curve.

What To Consider When Calibrating Pressure Gauges

When it comes to the calibration of pressure gauges these five factors will help you when wondering what to consider when calibrating pressure gauges: 

1. Condition

Dirt inside a gauge can harm pressure gauge calibration equipment, which makes it important to clean the gauge prior to calibration. Look out for any signs of leakage and corrosion to the body, loose needles, or damaged sockets and threads. If you observe any of these issues, a replacement may be a more realistic option than calibration.

2. Test equipment

The reference measurement instrument must be traceable and more accurate than the pressure gauge itself. A calibration involves checking values throughout the measuring range, zero-point, intermediate values, and full-scale value. Digital pressure gauges deliver the best reliability, with an average accuracy of 0.1% or 0.05%.

3. Accuracy

Pressure gauges come in a variety of accuracy classes. Specifications are typically referenced by “% of range”, which means if the accuracy class is 1% and the scale range is zero to 100 psi, the accuracy will be ± 1 psi. Get to know the accuracy classes of your pressure gauges to guarantee the most accurate calibration possible.

4. Range

The pressure media used in the calibration of pressure gauges depends on the media that is normally employed in the process, as well as the pressure range. Low-pressure pressure gauges can be calibrated using air or gas. However, as the pressure range gets higher, it is more practical – and safer –  to use liquid as the media.

5. Tolerance

If any discrepancies identified as part of the calibration process are greater than the defined tolerance, the pressure gauge will either require some adjustment or be taken out of service altogether. Your GNW technician can provide evidence-based advice regarding the best course of action for all your calibrated pressure gauges.

Pressure Gauge Calibration Company

Given how vitally important pressure gauges are to many industrial processes, it is all too obvious how crucial and effective the regular calibration of pressure gauges can be for your process efficiencies, site safety and bottom line. Now that you know what to consider when calibrating pressure gauges, and some of the main errors in pressure gauges, you can see the true value of getting your pressure gauges calibrated by the experts here at GNW.

GNW offers superior calibration services and supplies all types of instrumentation and measuring equipment. For over 40 years, we have built an enviable reputation for the high-quality production and repair of pressure gauges, calibration equipment, and more. Using the latest pressure gauge calibration equipment, we can calibrate everything from steam pressure gauges to air pressure gauges and hydraulic pressure gauges.   

We offer a range of quality services that ensure accurate results. Our on and off-site calibration and certification is designed to help you achieve complete accuracy from your instrumentation, and our other services, such as repairs and manufacture of custom instrumentation, can add value to your business. For more information, or to speak to one of our technical experts, please contact us on +44 (01704) 536 010 or info@gnw.co.uk