Selection of Calibration Range for Pressure Gauge

Most of the time we end up selecting wrong calibration range for pressure gauge if proper standard & thumb rule is not followed.

Due to variety of operating & design pressures, calibration range is unique for each pressure gauge.

1. Most important thing in selecting calibration range is to ensure that normal operating pressure is around middle of selected calibration range.
   To be precise, normal operating pressure should fall between 40% to 70% of selected calibration range. This is to ensure that pressure gauge pointer
   Always stay in the middle portion of scale. Which is comfortable for taking reading & gives sufficient margin in case pressure varies on both sides.
2. We should not select any pressure range which suits above condition. Calibration range shall be selected from standard calibration ranges which closely suits above conditions.
   Standard calibration ranges are accepted all over industry. Due to Standard calibration ranges vendor can reduce the types of pressure gauges to be
   Manufactured & also can maintain inventory.
3. Standard calibration ranges are provided in standard IS-3624. This standard provides very useful chart in which we can find out standard calibration range for
   Given operating pressure.
4. What happens if we select wrong calibration range?. Generally pressure gauge is custom made for calibration range. However, safety factor of 30% over the calibration
   Range is provided. For example, if we select calibration range of 0 -100 kg/cm2g the pressure gauge is suitable for up to pressure of 130 kg/cm2g. If design pressure of
   Pressure gauge falls within this pressure then it can be safely used for given application. However, if design pressure is beyond the 130% of calibrated span then
   We have to use gauge saver.
5. In general, pressure gauge dial colour is white with calibration range marked in black letters. Sometimes colour band is also used to identify different bands
   on pressure gauge dial. e.g. operating pressure range is marked with green band, above operating range is marked with red band and below operating range
   Is marked with yellow band.