When manufacturers define their accuracy as “% of reading”, they are describing the accuracy as a percentage of the reading currently displayed. For example, a gauge with 0.1 % of reading accuracy that displays a reading of 100 psi would be accurate to ± 0.1 psi at that pressure. At 50 psi, the same gauge would have an accuracy of ± 0.05 psi (twice as accurate).

When choosing an analog pressure gauge, two of the most important factors to consider are accuracy and pressure range. Most pressure gauges express their accuracy as a percentage of the gauge’s full scale. Full scale accuracy means that wherever you are reading within the scale, the error is the same. For example, a 1000 psi pressure gauge with an accuracy of ±1 % of scale will have an error of ±10 psi whether you measure 100 psi or 1000 psi. For these types of gauges, if your expected measurement is anywhere within the range, the error is consistent.

Temperature can have a large effect on gauge accuracy. If a gauge is temperature compensated then it will retain its specified accuracy while operating within the specified temperature range. Crystal digital gauges are temperature compensated for between -10 and 50°C (some -20 to 50°C). This means that during manufacture each and every gauge is calibrated in a special temperature controlled chamber and cycled through applied pressures throughout the temperature range. The readings are achieved and then each individual gauge is programmed to compensate for its specific changes at various temperatures. When checking another brand of gauge, remember to read the fine print and ask the question; “Is the gauge’s accuracy temperature compensated, and if so, over what temperature range?”.

Yes, they both use the same kind of pressure sensor which is fully isolated from your process fluid.

All gauges are tested in our specifically designed, environmentally controlled calibration laboratory. The type of test we run on a gauge depends on the accuracy required for the gauge. Typically, for lower accuracy gauges, we use the Crystal XP2i digital gauge as a reference gauge on a CPS Comparator, and through a process of applying pressure to both the reference gauges and the gauge under test simultaneously, we are able to check and report the indicated accuracy of the gauge under test via the known accuracy of the reference gauge. For higher accuracy gauges, we have both dead weight testers and pressure calibrators with high accuracy, to which the gauge under test is compared to. All calibrations are IANZ certified and traceable back to a National Standard.

Yes, we calibrate and IANZ certify both temperature and pressure gauges.

The only real way is to compare it to a known reference (i.e. a reference gauge or a calibrator). A sure sign of inaccuracy is when the gauge needle does not return to zero. However, often you cannot tell by simple observation. Incorrect gauge readings can lead to dangerous and life threatening situations. CPS manufacturers and supplies a range of pressure calibration equipment that enables you to do your own in house testing. Alternatively, you can courier, or drop, the suspect gauge into our office, and we can process it through our lab for calbration to give you a 100% conclusive answer.

IANZ stands for International Accreditation New Zealand. They are the national authority for the accreditation of technical, professional organisations including testing and calibration laboratories. View CPS’s IANZ accredited scope here

An IANZ certificate is internationally accepted and provides peace of mind that your instrument has been tested to the highest standards. IANZ accreditaton is only granted if an applicant meets the following conditions: 1) Competence and experience of staff 2) Integrity and traceability of equipment and materials 3) Technical validity of methods 4) Validity and suitability of results 5) Compliance with ISO management system standards.

Readability is the minimum amount you can accurately read a gauge to. For an analogue gauge this may be to part of a division (the increments marked on the gauge dial). For example, if a 100 bar gauge dial is marked by divisions which indicate 1 bar intervals, the resolution and readability is therefore 1 bar. But if the dial is sufficiently large enough, you may be able to read the gauge to part of a division (i.e. a ¼ of a division). Then the readability is ¼ bar. There are other factors that influence the readability of an analogue gauge such as parallax error and needle type. For a digital gauge, readability and resolution are usually the same. For example, if a digital gauge has a resolution (display) to 3 decimal places then the readability will be 0.001. However this applies only if you have a stable reading (i.e. if the 3rd decimal place is fluctuating wildly and too fast to read then in that application the readability is 2 decimal places). In the case of an application with fluctuating readings, the Crystal XP2i digital gauge has an averaging function which makes taking a reading to all decimal places possible in such applications.

Mechanical gauges will usually destroy themselves when pressure is applied 20 – 50 % above their full scale. Digital gauges differ in their overpressure abilities before failing. Crystal digital gauges’ unique silicon pressure sensor construction means they will easily handle two and a half times over pressure without damage. At 10% over pressure the Crystal gauge will display an error message. At CPS we have tested Crystal XP2I gauges to 10 times overpressure without damaging the gauge sensor – they still worked perfectly afterwards!

The gauges are most commonly filled with glycerine. Glycerine filling a gauge provides dampening against the effects of pulsating pressures or mechanical vibrations.

Yes, we have a wide range of digital gauges, hand held pumps and calibration equipment available for hire. Please click on the “gauge rentals” option under the Products category or click here!

While standard glycerine works well for most purposes, it struggles to endure high temperatures and may discolor over time. For applications involving extremely hot conditions—such as temperatures of 55°C or greater, silicone fill offers greater heat resistance and maintains its clarity more effectively.

In cold conditions below 0°C, silicone or a blend of glycerine and distilled water can be better alternatives to pure glycerine. Both options remain effective in frigid environments, maintaining reliable performance down to -40°C. In contrast, pure glycerine tends to become more viscous, reducing its effectiveness in such temperatures.