Investigations on Measurement Uncertainty and Stability of Pressure Dial Gauges and Transducers

Abstract

Several commercial instruments are available for pressure measurements. As per ISO stipulations, whenever such instruments are used for precise and accurate pressure measurements, it is obligatory on the part of measurement authority to indicate the quality of results. Stability of the pressure measuring instruments over the years is one of the important parameters in defining the quality of results quantitatively. Also, it helps the users to decide the optimum calibration interval of the particular instrument. In the present investigation, we have studied a number of analogue / digital pressure transducers / transmitters / calibrators and pressure dial gauges. The present paper describes the results of the studies carried out on several pressure dial gauges and transducers in the pressure range up to 500 MPa, calibrated several times over the years, as examples. A new approach is proposed for the establishment of measurement uncertainty for such instruments by characterizing the data obtained during calibration over the years using curve fitting.

A Computer Controlled Precision High Pressure Measuring System

“…Brought to you by | MIT Libraries Authenticated Download Date | 5/11/18 9:51 AM 201 the best fit line can be used to compute the equivalent pressure as reported elsewhere [18]. The full scale accuracy is found to be well within +0.015% except initial pressure point of 25 MPa where accuracy varies up to +0.025% but still within the manufacturer specified accuracy of the sensing element of +0.025%.…”

“…The full scale accuracy is found to be well within +0.015% except initial pressure point of 25 MPa where accuracy varies up to +0.025% but still within the manufacturer specified accuracy of the sensing element of +0.025%. The maximum accuracy of calibrator of +0.025% at 25 MPa is obvious at less than 10% of the full scale pressure [16,18].…”

“…The details of the working principle for such a sensing element and its mechanism are available in the literature [12][13]16]. The nominal frequency of pressure resonator is 38 kHz, which changes 10% as the applied pressure reaches the full scale of 275 MPa, while the nominal frequency of the temperature resonator of 172 kHz changes about 50 x 10 -6 / 0 C. The temperature compensated pressure output is computed using the following equations derived from the basic physical principle of fixed vibrating beam [12][13].…”

A Proposal for Simplifying the Method of Evaluation of Uncertainties in Measurement Results

“…The aim was to verify the reference value of the thermal conductivity coefficient declared directly by the manufacturer, namely for a transverse TM YTONG (lightweight concrete block) for building blocks P2 500 depending on material composition, density, moisture, and on specific sample thickness. The reference value of the coefficient λ = 0.130 W·m -1 ·K -1 was verified by measurement using a commercial instrument Isomet 2114, and on the basis of data obtained from a set of measurements; a degree of agreement in the form of evaluation of uncertainties in measurement results was determined [9].…”

Standardisation of pressure measurement using pressure balance as transfer standard

“…The pressure measured by LS is then least square fitted against the effective area of Test to determine the value of A 0t (zero pressure effective area) and λ t (distortion coefficient) of the Test. The measurement uncertainties in both the ranges are computed as per guidelines available in the literature [25][26][27][28][29]. The characterized values of the pressure measured using Eq.…”