Calibration of Bourdon Tube Pressure Gauge

Apparatus:

The equipments that we used are Bourdon gauge and dead weight tester, as shown in Figure 1.

Figure 1: Bourdon gauge and dead weight tester

Abstract:

This experiment was conducted to perform pressure calibration on a bourdon tube pressure gage using a dead weight tester. Weights are loaded on the piston and the indicated Bourdon tube pressure was read. . In this experiment, the error and percentage of error that occur inside the Bourdon tube will be calculated and compared to the true pressure that exerted by the total mass. According to the experimental results, the error that occurs in the Bourdon tube is inconsistent.

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Objective:

The objective of this experiment is to determine the accuracy in Bourdon Gauge and calibration requirement.

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Introduction

Bourdon Tube Pressure is widely used to measure pressure differences. The pressure sensing element is a tube of oval cross-section bent to a circular shape. One end of the tube is fixed to the gauge case and is connected to the fluid to be measured. The other end is closed and is free to move as it is connected via mechanical linkage and gear sector to a pointer. As measured fluid pressure increased above that of surrounding, the tube cross-sectional tends to straighten out and causes the tube deflects at this second end. This motion is transmitted via linkage to the pointer, which directly indicate on the calibrated scale or dial the gauge pressure. Calibration means checking the pressure gauge reading against a very accurate device.

One of the calibration device that is available in our lab is called “Dead Weight Tester”.

The Dead Weight Tester which is the device that supply highly accurate pressure for calibrating other compare to some other calibrating devices such as transducer, bottom-hole, and bourdon tube gauge. A tester may be used as a Dead Weight Gauge to determine unknown pressure by connecting the gas

pressure to the gauge connector through suitable tubing and a valve exact regulation of the supply pressure to the tester is obtained by balancing the force exerted by the

fluid pressure on a piston of know area against weight of known mass. A tester’s weight and a

piston are calibrated in sets to give an accuracy of 0.1% which is 1 pound in 1000 pounds. The most accurate instrument available for measurement of pressure above the range where monometers may be used is the Dead weight Tester. This type of terter operates on the principle balancing a known mass against the forced exerted by an exact balance is achieved, the unknown pressure P is equal to mass, M of the weight divided by the area, A of the piston, according to the formula:

p=f/a

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Theory

By using know pressure, variation in pressure sensor reading may be calibrated to give a gauge reading in engineering units. By applying mass to a column of fluid, the pressure produced is: P =

Where F= gM and A=

P = the pressure at the bottom of the piston F = force applied to the liquid in the calibrator cylinder M = the total mass including the piston g = the acceleration due to gravity A = the area of the piston Using SI units, the units of pressure are Newtons per square meter (N/m², also known as Pascals). To obtain the pressure in N/m², M must be in kg, g in m / s² and d in m.

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Procedure

Firstly, the weight of the piston and its cross-sectional area should be noted. While measuring the weight and the cross-section area water is poured into the cylinder until is full to the overflow level. Meanwhile, make sure that there is no air trapped in the tube by tilting and gently tapping the

apparatus. Next, the piston is then replaced in the cylinder and allowed to settle. Next, a spirit level placed on the platform at the top of the piston may be used to ensure that the cylinder stand quite vertically. After all the instrument had settled, weights are now added in convenient increments, and at each increment the pressure gauge reading is observed. To guard against the piston gently while the pressure gauge is being used. This procedure is repeated by increasing the weights. After that, this procedure is repeated again by decreasing the weights.