FA18-BME-030 COMSATS University Islamabad, Wah Campus Department of Mechanical Engineering NAME: - MUHAMMAD AMMAR NASIR REG NO: - FA18-BME-030 SECTION: - 6A SUBJECT: - INSTRUMENTATON AND MEASUREMENT LAB LAB REPORT: - 1st SUBMITTED TO: - SIR ENGG NADEEM IQBAL FA18-BME-030 Experiment no 01: To find out pressure with a Dead weight tester and compare it with theoretical results? Objective: The objective of this experiment is to find out the pressure using a Dead weight tester and compare it with theoretical results. Apparatus: • Dead weight tester apparatus. • Calibrated dead weights. Theory: Dead Weight Tester uses known traceable weights to apply pressure to a fluid for checking the accuracy of readings from a pressure gauge. A dead weight tester is a calibration standard method that uses a piston cylinder on which a load is placed to make an equilibrium with an applied pressure underneath the piston. Deadweight tester are so called primary standards which means that the pressure measured by a deadweight tester is defined through other quantities: length, mass, and time. Typically, deadweight testers are used in calibration laboratories to calibrate pressure transfer standards like electronic pressure measuring devices. The mechanism of the gauge is shown in the figure below. A tube, having a thin wall of oval cross section, is bent to a circular arc encompassing about 270 degrees. It is rigidly held at one end, where the pressure is admitted to the tube, and is free to move at the other end, which is sealed. When pressure is admitted, the tube tends to straighten, and the movement at the free end operates a mechanical system which moves a pointer round the graduated scale - the movement of the pointer being proportional to the pressure applied. The sensitivity of the gauge depends on the material and dimensions of the Bourdon tube; gauges with a very wide selection of pressure ranges are commercially available. FA18-BME-030 Formula: The formula on which the design of the apparatus is based basically is expressed as follows: F=mg [N] P=F/A [Pa] So here. F= force applied on piston [N] m= mass [kg] g=acceleration due to gravity = 9.8 P=reference pressure A= effective area Procedure: 1. 2. 3. 4. 5. 6. 7. 8. Open cylinder cap bolt. Fill cylinder with oil. Open cylinder oil valve. Close cylinder cap bolt. Close cylinder oil valve. Hydraulic oil will move to piston cylinder. Insert piston. Apply weight and note down reading. FA18-BME-030 To check the zero point of the manometer, proceed as follows: 1. 2. 3. 4. Press the piston out of the cylinder. Remove the piston and weight support. Adjust the oil level in the open cylinder until the cylinder is filled up. The manometer being tested should now indicate zero, as it is only subject to ambient pressure. 5. Assemble Bourdon's pressure gauge with dead weight tester. 6. Apply pressure in terms of weights on table and measure the value of it on pressure gauge. 7. Repeat the procedure for ascending and descending weights on table and corresponding. Result: Sr.# Applied load (Kg) Applied (N) 1 2 3 4 5 0.5 1 2.5 3.5 4.5 4.905 9.8 24.5 34.3 44.145 load Area (m2) 3.46185*10-4 3.46185*10-4 3.46185*10-4 3.46185*10-4 3.46185*10-4 Theoretical pressure (N/m2) 14168.72 28308.5 70771.4 99079.9 127518.52 Practical pressure (N/m2) 14375 28538 70881 99088 131018 Discussion: Two different kinds of error may normally expect in a gauge of this type. Firstly, there is a possibility of hysteresis, friction and backlash which will yield smaller gauge readings when the pressure is increasing than when it is decreasing. Secondly, there is error due to the scale being marked off incorrectly. It will be found that this error increases to a maximum of around 2.5% of the full-scale reading. This is acceptably small for many engineering purposes, although gauges with an error of only 0.5% of the full-scale reading are commercially obtainable. Conclusions: To ensure proper calibration, measurement tools must have a reliable system setup that does not introduce sources of error to the device. The pressure gauge could not be accurately calibrated with the apparatus used in this experiment due to several sources of error. These sources include, but are not limited to leakage, poor FA18-BME-030 lubrication, trapped air, mechanical fatigue, poor weight calibration, differential dead weight masses, and general user error. Upon repeating this experiment, a thoroughly sealed piston-cylinder device should be used along with a uniform set of dead-weights. In addition to this, a high-lubricity fluid should be used instead of water to prevent any restricted motion. With these adjustments, the experiment may be repeated and re-evaluated as a reliable calibration method. Reference: https://www.sika.net/en/products/sensors-and-measuring-instruments/mechanical-pressuregauges/bourdon-tube-pressure-gauges.html https://www.wika.us/landingpage_bourdon_tube_pressure_gauge_en_us.WIKA https://www.wika.com/en-en/lp_bourdon_tube_pressure_gauge.WIKA