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Calibration is a procedure to maintain accuracy of an instrument. The measured value of an instrument is compared to a known value or preferably to standards. The deviation of the measured quantity from the standard value is minimized through the calibration process. Accurate calibration will teach an instrument to produce accurate results with unknown samples. I fact, the purpose of all instruments is to measure unknown samples accurately during normal usage.

There are two kinds of measurements, one is direct, and the other is indirect measurements. Some physical and chemical quantities cannot be measured directly, and these are to be measured indirectly. Like flow can never be measured directly, it is always measured indirectly. Differential pressure transmitters measures physical quantities indirectly and then infer the result to find out the actual physical quantity.

Differential pressure transmitters are used to measure Flow, Density, Viscosity and Level etc. of liquid. How one single instrument will be used to measure so many different physical quantities? In all these cases, the DP Transmitter will measure the differential pressure in some form or other and then the result is interpolated to get the desired physical quantity.

This means, the DP Transmitter is to be calibrated differently to measure the particular physical quantity.

There are different methods of calibration like re-ranging, dry calibration and wet calibration. The choice of calibration methods will entirely depend on the application of the DP Transmitter. Let’s try to understand the difference between these three calibration methods. To do this, we will first find out how to perform DP Transmitter calibration by these calibration methods.