Pressure gauges are pressure measurement instruments that are built with Bourdon tube, diaphragm or capsule, and consist of pointer needle and pressure scale. As the pressure increases, the pointer moves across the scale, and that’s how an operator is able to calculate the pressure in an application. Just like many other measurement devices, pressure gauges also require calibration at regular intervals. In this blog, we will discuss the requirements and procedure of pressure gauge (analog) calibration.
Requirements
Gauge Comparator –A gauge comparator is used as a source of hydraulic pressure required for calibration. It should be able to provide sufficient full-scale and linear pressure to the unit under calibration (UUC).
Master Pressure Gauge – Also known as reference gauge, a master gauge is the most important equipment in any calibration. Better the accuracy, more accuracy of the calibration results. Master gauge for pressure gauge calibration must have at least 2 times better accuracy than the gauge to be calibrated. Also, the resolution on the least count of the master gauge must be better.
Controlled Conditions – The device along with the master pressure gauge must be kept in controlled environments for not less than 2 hours before calibration.
Procedure
Step 1 - The calibration test points are noted down (25%,50%,75%, and 100% of span).
Step 2 - The master gauge and test gauge are fixed on the gauge comparator.
Step 3 - Preloading. Full-scale pressure is applied to the test gauge slowly and after some time, the pressure is released to zero.
Step 4 - The readings of UUC and master gauge are observed on each calibration point in both pressure increasing and decreasing cycles.
Step 5- Based on the observations, the measurement uncertainty, and final results are calculated.
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