Lab 3 Static Calibration of Electronic Pressure Transmitters using Manometers February 1, 2013 Group 0 Miles Greiner Lab Instructors: Michael Goodrick and Alyssa Hawthorne

Abstract The purpose of this lab is to –Calibrate an electronic pressure transmitter using an inclined-well monometer, and –Interpret the manometer manufacturer’s accuracy specification. The best estimate for the true pressure head in terms of the transmitter reading is: –h = 1.015h T inch H 2 O, with a confidence interval of S T,M = ± inch-H 2 O (68%) –The maximum error in the reading is inch H 2 O, which is roughly equal to the manufacturer’s specification. The manufacturer stated manometer uncertainty is 6 times larger than the value of S M,T, corresponding to a nearly 100% confidence level. The manufacturer’s specified uncertainty is in the same order of magnitude of the error measures determined in this experiment.

Table 1 Equipment Specifications and Calibration The manometer is used to calibrate the transmitter because, after two years, the manometer’s uncertainty is smaller.

Table 2 Calibration Data This table shows one cycle of increasing and decrease pressure calibration data. The transmitter pressure head was determined from the measured current using the manufacture specified equation in Table 1 The transmitter pressure head reading did not return to zero at the end of the descending cycle.

Fig. 1 Calibration Data and Linear Fit The transmitter reading is consistently lower than the manometer-indicated pressure. Standard errors of the estimates for the transmitter and monometer are both S T,M = inch-H 2 O = S M,T The manufacturer stated accuracy (0.06 inch-H 2 O) for the transmitter is 6 times larger than S M,T, corresponding to a nearly 100% confidence level

Fig. 2 Error Error in manometer reading increases with pressure Maximum error magnitude (0.062 inch H 2 O) is roughly equal to the manufacturer specified accuracy (0.06 inch H 2 O)

Fig. 3 Calibration Deviation S T,M characterizes the deviations over the full range of h M The ascending deviations are generally positive while the descending ones are negative, which may be caused by hysteresis. There are no systematic deviations form the fit correlation, indicating the instrument response is linear.

Interpretation of Measurement Question