Instrument Element Mechanism PDF

Malaysian Institute of Aviation Technology Issue: 01 Revision: Module 11.4.3 1 00  Malaysian Institute of Aviation Technology Issue: 01 Module 1 2 Revision: 00  Malaysian Institute of Aviation Technology Issue: 01...

Malaysian Institute of Aviation Technology Issue: 01 Revision: Module 11.4.3 1 00  Malaysian Institute of Aviation Technology Issue: 01 Module 1 2 Revision: 00  Malaysian Institute of Aviation Technology Issue: 01 Module 1 3 Revision: 00  Malaysian Institute of Aviation Technology Issue: 01 Module 11.4.3 4 Revision: 00  Malaysian Institute of Aviation Technology Issue: 01 Module 11.4.3 5 Revision: 00  Malaysian Institute of Aviation Technology Objective 1: CLO2 To describes the 4 elements and mechanisms of instrument. Issue: 01 Module 13 6 Revision: 00  Malaysian Institute of Aviation Technology Issue: 01 Module 13 7 Revision: 00  Malaysian Institute of Aviation Technology 8 Issue: 01 Revision: 00  Malaysian Institute of Aviation Technology Issue: 01 Revision: 9 00  Malaysian Institute of Aviation Technology Measure the value of the physical qty in terms of small translational or angular displacement. Exhibit the value of the measured qty by relative position of a pointer. Detect changes Displacement are magnified the value of and transmitted. physical Issue: 01 quantity Revision: Module 13 10 00 or condition. 1 1 Malaysian Institute of Aviation Technology Measuring Elements Detecting Element which detect any changes in pressure. ie: Pressure head, static port. Measuring Element measures changes in pressure material used is either phosphor-bronze, beryllium-bronze or beryllium-copper Capsule – Low pressure (Max 14.7psi) Diaphragm – Low pressure (Max 14.7psi) Bellow – Med pressure (Max 600psi) Bourdon Tube – High pressure (Max 3,000psi)  Malaysian Institute of Aviation Technology Coupling Element which couples (joint) the measuring element to the indicating element. - Mechanical Coupling - Magnetic Coupling - Fluid Coupling Indicating Element measures the value of the transmitted quantity using a pointer or index rotating over a scale graduated in feet, knots, gallon, rpm etc. 1 3 Elements of Pressure Measuring Instrument Malaysian Institute of Aviation Technology 1 4 Pitot Head Malaysian Institute of Aviation Technology 1 5 Static Ports Malaysian Institute of Aviation Technology 1 6 Malaysian Institute of Aviation Technology Atmospheric Measurement Mercury Barometer A mercury filled tube inverted in a bowl of mercury. The amount of pressure exerted by the weight of air will make the mercury rises up in the tube. The height of mercury is measured in inches which represent the atmospheric pressure. Its measure absolute pressure. 1 7 Malaysian Institute of Aviation Technology Dead Weight Tester 1 8 Malaysian Institute of Aviation Technology Dead Weight Tester Use to calibrate direct reading pressure gauges. Base on principle Force = P x A Pressure = F / A P = pressure (psi), F = Force or mass (lbs), A = area (sq inch) Mass platform piston cross-section area = 1/8 sq inch Total mass of piston and platform = 1/8 lbs  If mass is added to the platform eg: 3 lbs 1 9 Malaysian Institute of Aviation Technology Differential Pressure Measurement Diaphragm A sheet of a semi-flexible material anchored at its periphery. The sheet is corrugated is to permit larger deflection. Made of beryllium and copper. Arranged so as to expose one side to the pressure being measured. The deflections being transmitted to pointer mechanism. 2 0 Malaysian Institute of Aviation Technology Absolute Pressure Measurement Capsule Made of two diaphragms placed together and joined at their edges to form a chamber which may be completely sealed or open to pressure source..  Malaysian Institute of Aviation Technology Aneroid Capsule An enclosed chamber made of beryllium and copper. Inside the chamber is vacuum or zero pressure. A decrease in ambient pressure will make the capsule expand and an increase in pressure makes the capsule contract. It is use for measuring absolute pressure Issue: 01 Module 11.4.3 21 Revision: 00 2 2 Malaysian Institute of Aviation Technology Differential Pressure Measurement Bellows Extension of the corrugated diaphragm principle. In operation it bears some resemblance to a helical compression spring. Made of beryllium and copper. 2 3 Malaysian Institute of Aviation Technology Bourdon Tube Bourdon Tube  For high pressure measurement.  Consist of elliptical cross-sectioned tube bent a curve or spiral.  When pressure is applied, the tube attempts to straighten.  The amount of the tube straightens is proportional to the amount of pressure inside the tube.  A choke or restrictor is fitted to the inlet to prevent surge pressures damaging the tube. 2 4 Malaysian Institute of Aviation Technology  Malaysian Institute of Aviation Technology 1. Name the 4 elements of an instrument. 2. What is the purpose of detecting element? 3. What is the purpose of measuring element? 4. What is the purpose of coupling element? 5. What is the purpose of indicating element? Issue: 01 Revision: Module 11.4.3 25 00  Malaysian Institute of Aviation Technology 1. The 4 elements of an instrument are detecting, measuring, coupling, and indicating elements. 2. The purpose of detecting element is to detect the changes of physical qty such as pressure, temperature, position, and speed. 3. The purpose of measuring element is to measure the changes of physical qty. 4. The purpose of coupling element to magnify, rectify, amplify the displacement and couple or transmit to the indicator. 5. The purpose of indicating element is to show/display/exhibit the measured value relative to position of the pointer or 26 scale.  Malaysian Institute of Aviation Technology 27 Issue: 01 Revision: 00  Malaysian Institute of Aviation Technology Issue: 01 Revision: Module 11.4.3 28 00  Malaysian Institute of Aviation Technology A screw joint linkage for the interconnection of Issue: 01 Revision: component parts. 29 00  Malaysian Institute of Aviation Technology Constructed as coupling element. It is a connection between input Issue: 01 displacement Revision: (couple) to output (indicating). Module 11.4.3 30 00  Malaysian Institute of Aviation Technology Issue: 01 Revision: Module 13 31 00  Malaysian Institute of Aviation Technology Gear mechanism Provide magnification of the measuring element for the pointer. Issue: 01 Revision: Module 11.4.3 32 00  Malaysian Institute of Aviation Technology Issue: 01 Revision: Module 11.4.3 33 00  Malaysian Institute of Aviation Technology Hairspring Serves as controlling devices against Issue: 01 00 Revision: deflecting force. Module 11.4.3 34  Malaysian Institute of Aviation Technology Avoid Jamming of the Gears PROBLEM SOLVE? Issue: 01 Revision: Module 11.4.3 35 00  Malaysian Institute of Aviation Technology Issue: 01 Revision: Module 11.4.3 36 00  Malaysian Institute of Aviation Technology Issue: 01 Revision: Module 11.4.3 37 00  Malaysian Institute of Aviation Technology 1. Name the 4 mechanism of an instrument. 2. What is the purpose of rod? 3. What is the purpose of lever? 4. What is the purpose of gear? 5. What is the purpose of hairspring? Issue: 01 Revision: Module 11.4.3 38 00  Malaysian Institute of Aviation Technology 1. Rod is a screw joint linkage for the interconnection of component parts. 2. Levers are constructed as coupling element. 3. Levers are used as a connection between input displacement (couple) to output (indicating). 4. The gear provides magnification of the measuring element for the pointer. 5. Hairspring serves as controlling devices against deflecting force. 6. Coil hairspring and anti-backlash gear used to prevent unstable effect of the pointer movements (backlash) 39