3 Transducers Automotive Engine Performance Transducers Topics covered

3. Transducers Automotive – Engine Performance Transducers Topics covered in this presentation: n Active and Passive Sensors n Common Sensor Types and Their Operation Class. Act SRS enabled.

3. Transducers Automotive – Engine Performance A sensor (transducer) changes a condition into an electrical signal. Sensor may be active or passive. Next >

3. Transducers Active Sensors Automotive – Engine Performance Two wire device. Generates own 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 Passive Sensors Automotive – Engine Performance Three wire device. Supplied with voltage from ECU. Sensor supply voltage Internal resistance changes with a change in conditions. +5 V 5 V 0 V Sensor Corresponding output voltage change is measured by ECU. Example - throttle position sensor. 0 V Output voltage 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 Passive Sensors Automotive – Engine Performance 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 5 V Sensor V W 0 V Internal resistance Output voltage Next >

3. Transducers Passive Sensors Automotive – Engine Performance Switch must be either open or closed. Supplied with voltage from ECU via resistor. Current limiting resistor +12 V 0 V Switch open, ECU measures 12 V. Switch closed, ECU measures 0 V. Example - brake pedal switch. 0 V 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) 12 V +12 V B) 6 V C) 5 V D) 0 V Switch 0 V

3. Transducers Sensor Types Automotive – Engine Performance Most common types: n Intake Air Temperature (IAT). n Manifold Absolute Pressure (MAP). n Engine Coolant Temperature (ECT). n Oxygen (O 2). n Mass Air Flow (MAF). n Throttle Position (TPS). n Crankshaft Position (CKP). n Camshaft Position. n Vehicle Speed (VSS). n EGR Position. n Brake Switch. n Oil Level Switch. n Knock. Next >

3. Transducers Oxygen Sensor (O 2) Wires to ECU Automotive – Engine Performance Located in exhaust downpipe. Measures oxygen content in exhaust gas and atmosphere. Produces output voltage corresponding to difference in oxygen levels. 0 volts = high oxygen content in exhaust gas. Heating element Sensor element 1. 4 volts = low oxygen content. Protective cap with gas intake slots V 0. 7 V 0. 3 - 0. 7 volts = ideal oxygen content. 0. 3 V 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) 0 V B) 0. 5 V C) 1. 4 V D) 5. 0 V

3. Transducers Engine Coolant / Intake Air Temp Sensors Automotive – Engine Performance ECT located in coolant. IAT located in incoming air. Reference voltage +V V W 0 V 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 (potentiometer), fixed to the throttle valve. Resistance changes with throttle position. Reference voltage +5 V 5 V TPS 0 V 0 V Output voltage ECU supplies sensor with voltage. Sensor output voltage changes with throttle position. ECU measures voltage to determine throttle position. Next >

3. Transducers Mass Airflow Sensor (MAF) Automotive – Engine Performance Mounted before 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 >

3. Transducers Crankshaft/Camshaft/Vehicle Speed Sensor Automotive – Engine Performance 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 >

3. Transducers Inductive pulse generators produce a voltage to create a trigger signal Automotive – Engine Performance • AC current is produced • + voltage • 0 voltage • - voltage • The trigger point is normally at 0 voltage Hillier

3. Transducers Automotive – Engine Performance Hall Effect V - NO POTENTIAL DIFFERENCE +

3. Transducers Automotive – Engine Performance Hall Effect V Magnetic field deflects the electron flow through the Hall chip, causing a potential difference to appear across the chip. + N S

3. Transducers Automotive – Engine Performance Hall effect Magnet Halls chip C A Rotor Vane Halls chip B D • Current flow from A to B • Current flows from C to D (trigger current) • Current flows from A to B • With halls effect the current is turned on and off only to produce a square wave

3. Transducers Automotive – Engine Performance Low Oil/Brake Fluid Level Sensor Oil level switch located in sump. 12 V Lamp off ABS, ECU monitoring point Brake fluid switch located in reservoir. Switch open when fluid level normal, lamp is off. 12 V Switch open Fluid level okay Lamp on Switch closed Fluid level low Switch closed when fluid level low, lamp is on. Next >

3. Transducers Knock Sensor Automotive – Engine Performance Mounted on the engine. Detects vibrations that indicate abnormal combustion (knock). Output voltage +V Produces output voltage proportional to knock strength. Uses Piezo Crystal. 0 V Knock sensor ECU retards ignition when abnormal combustion is detected. Next >

3. Transducers Question 7 Automotive – Engine Performance What does a knock sensor detect? A) Gas concentration B) Abnormal combustion C) Wheel movement D) Gas level

3. Transducers Summary Automotive – Engine Performance You should be aware of: n Active and Passive Sensors n Common Sensor Types and Their Operation End >