sensors , LE THANH PHUC

University of Technical Education Ho Chi Minh City SENSORS Le Thanh Phuc Faculty of Automotive Engineering Email: thanhphucckd@gmail.com Thermistors Thermistors are commonly used to measure the temperature of liquids and ambient air A thermistor is a solid-state variable resistor made from a semiconductor material that have very reproducible resistance verses temperature properties Thermistors There are two types of thermistors: negative temperature coefficient (NTC) thermistors and positive temperature coefficient (PTC) thermistors NTC thermistors reduce their resistance as the temperature increases, while PTC thermistors increase their resistance as the temperature increases The NTC is the most commonly used Thermistors Thermistors: Water Temperature Sensor The water temperature sensor is typically located near the cylinder head water outlet Position and Motion Detection Sensors Many electronic systems require input data concerning position, motion, and speed Most motion and speed sensors use a magnet as the sensing element or sensed target to detect rotational or linear speed Potentiometer A common position sensor used to monitor linear or rotary motion is the potentiometer A potentiometer is a voltage divider that provides a variable DC voltage reading to the computer Potentiometer: Vane type airflow meter The vane type air flow meter is located in the air induction system inlet pipe between the air cleaner and the throttle body Potentiometer: Vane type airflow meter The potentiometer converts the mechanical movement of the measuring plate into a variable voltage signal Potentiometer: Vane type airflow meter Movement of the measuring plate and the analog voltage signal produced by this sensor are proportional to the volume of air entering the intake manifold 10 Mass Air Flow (MAF) Sensors Wheatstone Bridges A Wheatstone bridge is nothing more than two simple series circuits connected in parallel across a power supply When all four resistors have the same value, the bridge is balanced and the voltage sensor will indicate a value of volts 18 Mass Air Flow (MAF) Sensors 19 Mass Air Flow (MAF) Sensors The thermistor measures the temperature of the incoming air The hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control circuit An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by sending more current through the wire The electronic control circuit simultaneously measures the current flow and puts out a voltage signal (VG) in proportion to current 20 flow Manifold Absolute Pressure (MAP) Sensor In the Manifold Absolute Pressure (MAP) sensor there is a silicon chip mounted inside a reference chamber On one side of the chip is a reference pressure On the other side is the pressure to be measured 21 Magnetic Pulse Generator The components of the pulse generator are: A timing disc that is attached to the rotating shaft or cable The number of teeth on the timing disc is determined by the manufacturer and depends on application A pickup coil consists of a permanent magnet that is wound around by fine wire 22 Magnetic Pulse Generator 23 Magnetic Pulse Generator Position/speed sensors provide information to the ECM about the position of a component, the speed of a component, and the change in speed of a component 24 Magnetic Pulse Generator This system consists of a gear (reluctor wheel), that is mounted on the distributor shaft, has a number of teeth equaled to number of engine cylinders, permanent magnet and pick up coil wrapped around the magnet 25 Hall-Effect Sensors Based on the principle that if a current is allowed to flow through thin conducting material that is exposed to a magnetic field, another voltage is produced 26 Hall-Effect Sensors 27 Hall-Effect Sensors 28 Hall-Effect Sensors 29 Switch Inputs Switches are simplest of all input devices The computer monitors the two states of the switch by measuring the voltage on the sense circuit There are two types of voltage sensing circuits used with switches; the pull-down circuit and the pull-up circuit 30 Switch Inputs 31 Switch Inputs: Stop switch 32 [...]... (reluctor wheel ), that is mounted on the distributor shaft, has a number of teeth equaled to number of engine cylinders, permanent magnet and pick up coil wrapped around the magnet 25 Hall-Effect Sensors Based on the principle that if a current is allowed to flow through thin conducting material that is exposed to a magnetic field, another voltage is produced 26 Hall-Effect Sensors 27 Hall-Effect Sensors 28... air downstream, very similar to the wake created in the water after a boat passes 13 Karman airflow meter 14 Karman airflow meter 15 Mass Air Flow (MAF) Sensors The Mass Air Flow Sensors converts the amount of air drawn into the engine into a voltage signal 16 Mass Air Flow (MAF) Sensors The air flow sensor is located directly in the intake air stream, between the air cleaner and throttle body where... measure incoming air 17 Mass Air Flow (MAF) Sensors Wheatstone Bridges A Wheatstone bridge is nothing more than two simple series circuits connected in parallel across a power supply When all four resistors have the same value, the bridge is balanced and the voltage sensor will indicate a value of 0 volts 18 Mass Air Flow (MAF) Sensors 19 Mass Air Flow (MAF) Sensors The thermistor measures the temperature... the rotating shaft or cable The number of teeth on the timing disc is determined by the manufacturer and depends on application 2 A pickup coil consists of a permanent magnet that is wound around by fine wire 22 Magnetic Pulse Generator 23 Magnetic Pulse Generator Position/speed sensors provide information to the ECM about the position of a component, the speed of a component, and the change in speed... incoming air The hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control circuit An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by sending more current through the wire The electronic control circuit simultaneously measures the current flow and puts out a voltage signal (VG) in... current is allowed to flow through thin conducting material that is exposed to a magnetic field, another voltage is produced 26 Hall-Effect Sensors 27 Hall-Effect Sensors 28 Hall-Effect Sensors 29 Switch Inputs Switches are simplest of all input devices The computer monitors the two states of the switch by measuring the voltage on the sense circuit There are two types of voltage sensing circuits used with ... airflow meter 15 Mass Air Flow (MAF) Sensors The Mass Air Flow Sensors converts the amount of air drawn into the engine into a voltage signal 16 Mass Air Flow (MAF) Sensors The air flow sensor is located... water outlet Position and Motion Detection Sensors Many electronic systems require input data concerning position, motion, and speed Most motion and speed sensors use a magnet as the sensing element... balanced and the voltage sensor will indicate a value of volts 18 Mass Air Flow (MAF) Sensors 19 Mass Air Flow (MAF) Sensors The thermistor measures the temperature of the incoming air The hot wire