Evaluation of Associated Uncertainties in Calibration of Direct Pressure Indicating Electromechanical Devices

A wide range of direct pressure measuring electromechanical transducers is now commercially available in the market. In such electromechanical type direct indicating devices, the applied pressure is directly measured by a sensing element with a suitable mechanism into an analog / digital electrical signal in terms of voltage, current or frequency. The generation of such signals is based upon some electromechanical effects viz. inductive, capacitive, resistive, piezoelectric, piezoresistive, reluctive, resonative and optoelectric etc. A wide range of such pressure measuring instruments is now commercially available in the market. The high-pressure technology and new applications demand that the best instrumentation should ensure the lowest measurement uncertainty, particularly in the fluid media. The calculation of the calibration results and associated uncertainties is a complex matter involving many influencing quantities. The present paper describes a novel method for evaluating uncertainty in pressure measurement using electromechanical type direct pressure indicating devices through statistical analysis of errors. The method of evaluation of associated uncertainties is in line with ISO and EA Guidelines on the evaluation and expression of uncertainty in measurement. The results thus obtained are compared with the results obtained by using standard technique described in EA guidelines. Both the methods are quite comparable.