Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Resistive opto-isolator wikipedia , lookup
Stray voltage wikipedia , lookup
Alternating current wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Buck converter wikipedia , lookup
Voltage optimisation wikipedia , lookup
Mains electricity wikipedia , lookup
3. Transducers Automotive – Engine Performance Transducers Topics covered in this presentation: Active and Passive Sensors Common Sensor Types and Their Operation 3. Transducers Automotive – Engine Performance Transducers A sensor (transducer) changes a condition into an electrical signal. Sensor may be active or passive. Next > 3. Transducers Automotive – Engine Performance Active Sensors Two wire device. Generates own voltage signal. Voltage signal Voltage signal connects to ECU input. ECU processes input signal into digital information. Active sensor Trigger wheel 2 wire output ECU operates outputs, depending upon digital information received. Example - inductive/magnetic pickup. Next > 3. Transducers Automotive – Engine Performance Passive Sensors Three wire device. Supplied with voltage from ECU. Sensor supply voltage Internal resistance Internal resistance changes with a change in conditions. +5V 5V 0V Sensor Corresponding output voltage change is measured by ECU. 0V Output voltage Example - throttle position sensor. Next > 3. Transducers Automotive – Engine Performance Question 1 The main distinction between an active and a passive sensor is that an active sensor generates its own voltage, a passive sensor must be supplied with a voltage. Is this true or false? Answer True or False. 3. Transducers Automotive – Engine Performance Question 2 The electronic control unit (ECU) has to convert all analogue signals to digital before processing them. Is this true or false? Answer True or False. 3. Transducers Automotive – Engine Performance Passive Sensors Two wire device. Current limiting resistor Supplied with voltage from ECU via resistor. Internal resistance changes with a change in conditions. Corresponding output voltage change is measured by ECU. Example - coolant temperature sensor. +V 5V Sensor V W 0V Internal resistance Output voltage Next > 3. Transducers Automotive – Engine Performance Passive Sensors Switch must be either open or closed. Supplied with voltage from ECU via resistor. Current limiting resistor +12V 12V 0V Switch Switch open, ECU measures 12V. Switch closed, ECU measures 0V. Example - brake pedal switch. 0V Output voltage Next > 3. Transducers Automotive – Engine Performance Question 3 The diagram shows a brake pedal switch and its connections to the ECU. What voltage will the ECU measure when the switch is closed? A) 12V +12V B) 6V Switch C) 5V 0V D) 0V 3. Transducers Automotive – Engine Performance Make a list of as many sensors as you can. 3. Transducers Automotive – Engine Performance Sensor Types Most common types: Intake Air Temperature (IAT). Manifold Absolute Pressure (MAP). Engine Coolant Temperature (ECT). Oxygen (O2). Mass Air Flow (MAF). Throttle Position (TPS). Crankshaft Position (CKP). Camshaft Position. Vehicle Speed (VSS). EGR Position. Brake Switch. Oil Level Switch. Knock. Next > 3. Transducers Automotive – Engine Performance Oxygen Sensor (O2) Wires to ECU Located in exhaust downpipe. Measures oxygen content in exhaust gas and atmosphere. Produces output voltage corresponding to difference in oxygen levels. Heating element Sensor element 0 volts = high oxygen content in exhaust gas. 1.4 volts = low oxygen content. Protective cap with gas intake slots V 0.7V 0.3 - 0.7 volts = ideal oxygen content. 0.3V Heating element speeds up sensor operation from cold. Rich Lean 14.7:1 Air/fuel ratio Next > 3. Transducers Automotive – Engine Performance Question 4 What is an IDEAL voltage for an oxygen sensor, located in the exhaust downpipe, to produce? A) 0V B) 0.5V C) 1.4V D) 5.0V 3. Transducers Automotive – Engine Performance Engine Coolant / Intake Air Temp Sensors ECT located in coolant. IAT located in incoming air. Reference voltage +V V W 0V Engine coolant temperature sensor Resistance and voltage changes with temperature Sensor resistance changes with temperature change. Resistance change causes voltage change at ECU input. ECU measures voltage to determine temperature. Next > 3. Transducers Automotive – Engine Performance Question 5 The ECU measures the change in current, in the resistive sensor, to monitor the intake air temperature. Is this true or false? Answer True or False. 3. Transducers Automotive – Engine Performance Throttle Position Sensor (TPS) Variable resistor, fixed to the throttle valve. Resistance changes with throttle position. Reference voltage +5V 5V TPS 0V 0V Output voltage ECU supplies sensor with voltage. Sensor output voltage changes with throttle position. ECU measures voltage to determine throttle position. Next > Throttle position switch 3. Transducers Automotive – Engine Performance 1.Switch type, which have contacts for both idle and full throttle positions but no other information. Throttle position switch 3. Transducers Automotive – Engine Performance • Potentiometer type, give the ECU accurate information on the throttle position because it gives a signal for all throttle positions. 3. Transducers Automotive – Engine Performance Describe the 2 ways that the throttle is controlled. 1. By cable that links the throttle body to the accelerator pedal. 2. “Fly by wire” where the ECU operates the throttle valve in relation to the driver’s accelerator pedal position. 3. Transducers Air flow meter. Automotive – Engine Performance Engine load is sensed by the engine load sensor – e.g. air flow meter Air cleaner Air drawn into intake system Engine load is dictated by the position of the throttle butterfly – i.e. driver demands Automotive – Engine Performance 3. Transducers Air Flow Meter 3. Transducers Automotive – Engine Performance EFI components - input signal flow sensor Vane type air Oscilloscope is better!! Earth terminal --v Signal terminal Supply voltage terminal ECU Automotive – Engine Performance 3. Transducers Air Flow Meter 3. Transducers Automotive – Engine Performance Mass Airflow Sensor (MAF) Mounted before the throttle valve on EFI engines. Measures mass of air entering engine. Contains ‘hot wire’ which is heated by current flow. Output to ECU Airflow cools hot wire, changing current flow. Air in Electronics module outputs signal to ECU corresponding to current change. Change in current is proportional to airflow into engine. Electronics module Next > Automotive – Engine Performance 3. Transducers Hot wire metering. Automotive – Engine Performance 3. Transducers Air Mass Meter 3. Transducers Automotive – Engine Performance Pressure/vacuum sensing • This system uses a manifold absolute pressure (MAP) sensor to measure the manifold depression. Manifold depression is created by the pumping actions of the pistons. The MAP sensor measures the manifold pressure in the inlet manifold which changes with the engine’s load and throttle position. The MAP sensor consists of a diaphragm and a piezoelectric circuit. Automotive – Engine Performance Manifold 3. Transducers Absolute Pressure Sensor (Map) Automotive – Engine Performance 3. Transducers • When is manifold depression at its highest? • At idle speed, when the throttle plate is fully closed • When is manifold depression at its lowest? • At full throttle, when there is no restriction to the air flowing into the cylinders. 3. Transducers Automotive – Engine Performance Crankshaft/Camshaft/Vehicle Speed Sensor Mounted next to trigger wheel with small air gap. Sensor (inductive/magnetic pickup) contains magnet and coil. Movement of tooth towards sensor disrupts magnetic field and produces voltage in coil. Inductive/ magnetic pickup Output voltage Trigger wheel Movement of tooth away from sensor disrupts magnetic field and produces opposite polarity voltage. Output frequency is determined by trigger wheel speed. Next > Automotive – Engine Performance 3. Transducers Positive voltage Negative voltage • Crank Angle Sensor gives information on the speed and position of the crankshaft to the ECU to control ignition timing, and injection sequencing. The control unit can then trigger the ignition, and injection, to suit operating conditions. Automotive – Engine Performance 3. Transducers • The camshaft position sensor provides definitive positional information because the camshaft only rotates once per engine cycle. 3. Transducers Automotive – Engine Performance Question 6 A vehicle speed sensor produces a signal whose frequency is proportional to the speed of the vehicle. Is this true or false? Answer True or False. 3. Transducers Automotive – Engine Performance Knock Sensor Mounted on the engine. Detects vibrations that indicate abnormal combustion (knock). Output voltage +V 0V Produces output voltage proportional to knock strength. Knock sensor ECU retards ignition when abnormal combustion is detected. Next > 3. Transducers Automotive – Engine Performance Question 7 What does a knock sensor detect? A) Gas concentration B) Abnormal combustion C) Wheel movement D) Gas level Automotive – Engine Performance 3. Transducers Lambda sensor • What information does this sensor give to the ECU? • It detects left-over oxygen in the exhaust gas, and sends the data to the control unit. What does the ECU do with the information from this sensor? The control unit uses it to fine-tune the pulse it sends to the fuel injectors. 3. Transducers Automotive – Engine Performance Summary You should be aware of: Active and Passive Sensors Common Sensor Types and Their Operation End >