Ashford Instrumentation Ltd - Calibration Certificates & Test Certificates For Pressure Gauges

Calibration Certificates & Test Certificates For Pressure Gauges

Point To Point Calibration Certificates & Standard Test Certificates can be supplied with our entire range of pressure gauges. We have our own in-house calibration workshop than can certify instruments up to 1500 Bar. Depending on the application and the instrument to be calibrated we offer two types of certification, both of which are fully traceable to National Standards. To help in understanding our calibration service and to decide which calibration service you require the following edited extract from our Terms & Conditions will help.

Calibration of Pressure Gauges (Appendix 1 of our Terms & Conditions)

This document has been produced by Ashford Instrumentation to bring clarity to the work we perform under the general description of “calibration of pressure gauges”. The National Physical Laboratory in their publication “Guide to the Measurement of Pressure & Vacuum” offered the following definition under Section 7.1 - What Is Calibration:

“Sometimes the word “calibration” is misused to describe the process of altering the performance of an instrument to ensure that the values it indicates are correct within specified. This is an “adjustment”, not a calibration, although the nature and magnitude of the adjustment is often determined by a pre-adjustment calibration, sometimes known as an “as found” calibration. When adjustment is undertaken, the full procedure is thus first calibration followed by adjustment and then second calibration”.

Based upon the above guidance, Ashford Instrumentation offer the following service when we receive a pressure gauge for calibration.

An initial “As Found” calibration is made to assess whether the gauge is within it's stated accuracy class. There is a standard charge for this service regardless of what this calibration reveals.

If the instrument is found to be within it's accuracy class a Full Calibration Certificate can be supplied which is directly traceable to National Standards.

Please note that for pressure gauges with an accuracy class between 0.25% and 0.6% this will show a minimum of 10 points up and down scale, for accuracy class between 1% and 2.5% a minimum of 5 points and for class 4 a minimum of 4 points. This is in accordance with EN-837-1 Section 10.2.

Please also note that pressure gauges with a pointer stop, the accuracy class will cover 10% to 100% of the range. For pressure gauges with a free zero, the accuracy class will cover 0% to 100% of the range and zero shall be used as an accuracy check point. This is in accordance with EN-837-1 Section 6. Details of nominal size (diameter) compared to accuracy class can also be found in this Section of EN-837-1.

After the “As Found” calibration, if the instrument is found to be outside it's permissible accuracy class we may attempt an adjustment depending on the condition or construction of the gauge. There is a minimum charge for this depending on what adjustment is required. Please note that we are under no obligation to perform an adjustment and reserve the right to return any instrument after “As Found” calibration and charge accordingly.

After adjustment the gauge is calibrated again at an additional cost of and the appropriate Calibration Certificate produced.

Please note that during the adjustment we will only carry out work on the gauge appropriate to the calibration. We will not take on additional work which would normally be regarded as repair or refurbishment such as replacing broken windows, sealing glycerine leaks from the case, topping up with glycerine etc etc unless specifically told to do so. This additional work will be chargeable separately.

As well as offering the above calibration service which follows the guidelines of the European Standard EN837-1, we also offer a Test Service that falls outside the general calibration guidance of EN-837. Whilst following many of the best practices advised by EN-837, our Test Service is best described as an “Industrial Check of Calibration” and as such is charged at a lower rate. All the test equipment used is still fully traceable to National Standards but the number of test points is below that recommended by EN-827. Our Test Service (that results in us issuing our Standard Test Certification) should only be regarded as a general guide to the accuracy of the pressure gauges as we only check at 3 points on the scale. For an instrument with a zero stop this is usually at 25%, 50% and 75% of scale readings. For instruments with a free zero this is usually at zero, mid-scale and full scale.

Additional Information

For instruments with an accuracy class better than 1%, all calibrations are carried out at a reference temperature of 20C within +/-2C. For instruments of class 1 and above a reference temperature of 20C within +/-5C is observed.

Our in-house testing facility can accommodate pressures to 1000 Bar as well as full vacuum with a variety of process connections.

Unless pre-specified, all calibrations will be carried out on oil.

We have the facility to calibrate Oxygen & Acetylene gauges (and any other instrument not compatible with oil, or that bears the crossed oil can on dial) on distilled water to a pressure of 700 Bar. There is an additional surcharge of £10.00 for all oil free calibrations, including the “As Found” calibration.

All the certificates we issue have a unique serial number and the master calibration equipment used is traceable to National Standards. The control of this is under our ISO 9001:2000 Quality System.