Frequently Asked Questions:

Here you should find the answers to some commonly asked questions.
If you still unable to find your answer please drop us an email, If we can't help we will put you onto someone who can.

•   How does a Crystal digital pressure gauge work?
  • Crystal gauges incorporate a silicon chip pressure sensor. Under pressure the silicon will compress, but the crystalline structure of silicone means it will return perfectly to its original shape with high repeatability, once pressure is released. The silicone deformation under pressure is then converted to an electrical output.
•   What does "percentage of reading" mean?
  • “Percentage of reading” refers to the accuracy of the gauge and is how Crystal Digital gauges are rated. Most other gauges are rated by “percentage of full scale”. An example of percentage of reading: take a Crystal XP2i 0-10 bar pressure gauge. It’s very simple to calculate its accuracy. The gauge has an accuracy of +/- 0.1 % of the actual reading you are taking when measuring between 2 - 10 bar. So if the gauge is reading 5 bar its accuracy is +/- 0.005 bar (5 x 0.1% = 0.005). By comparison a 10 bar gauge with 0.1% of full scale accuracy at 5 bar would have an accuracy of +/- 0.01 bar (10 x 0.1% = 0.01) – this accuracy is constant throughout the gauges range. So at this pressure (5 bar) the XP2i is twice as accurate (i.e. half the error). Continuing with the XP2i example above, when measuring between 0 – 2 bar on the 10 bar gauge, the accuracy is +/- 0.02 % of the full scale, (i.e. 0.02 % of 10 bar = +/- 0.002 bar) – this is a constant accuracy for the lower 20% of the gauge.
•   What does "percentage of full scale" mean?
  • This is a common method of rating accuracy for mechanical and some digital gauges. For example, take a 10 bar gauge with an accuracy rating of 1 %. At whatever pressure you apply you will need to allow for a maximum error factor of +/- 0.1 bar. This is the constant error for the gauge regardless of the applied pressure. By comparison with a “percentage of reading”, the error changes dependent on the applied pressure, providing a higher accuracy (i.e. less error).
•   What does "temperature compensated" mean?
  • 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?”.
•   How fast do the Crystal gauges pick up peaks?
  • Under normal operating circumstances – three times per second. However, this can be easily be increased to as frequently as eight times per second, through the software ConFigXP™. Therefore, as long as the peak is a minimum of 125 milliseconds long, the sensor will register and display the peak.
•   Can an XP2i or M1 be used on liquids?
  • Yes, they both use the same kind of pressure sensor which is fully isolated from your process fluid.
•   How does CPS test my gauges?
  • 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.
•   Does CPS calibrate temperature gauges?
  • Yes, we calibrate and IANZ certify both temperature and pressure gauges.
•   How do I tell if my mechanical gauge is reading correctly?
  • The only real way is to compare it to a known reference (i.e. a reference gauge or a tester). A sure sign of inaccuracy is when the gauge needle does not return to zero. However, often you cannot tell by simple observation, although a ruptured pressure tank/ boiler is a good sign your gauge was not reading correctly. 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 will run the necessary tests and give you the answer.
•   What is IANZ?
  • IANZ stands for International Accreditation New Zealand. They are the national authority for the accreditation of technical, professional organisations including testing and calibration laboratories.
•   Why is an IANZ endorsed certificate preferable to a normal certificate?
  • 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.
•   What is readability?
  • 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.
•   How much overpressure can a gauge handle?
  • 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 self destructing. 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!
•   Why are the gauges liquid filled and what are they filled with?
  • The gauges are filled with glycerine. This provides dampening against the effects of pulsating pressures or mechanical vibrations.
•   Do you hire gauges?
  • Yes, we have a wide range of digital gauges, hand held pumps and calibration equipment available for hire. Please click on the "rent a gauge" option under the Pressure gauge category for more information.
•   Are prices inclusive or exclusive of GST?
  • Our prices are all exclusive of GST as most of our sales are to other companies.