Electronic Sensors and Components Flashcards

Flashcards reviewing electronic sensors, pressure sensors, speed and position sensors, potentiometers, rheostats, switches, and relays.

Diode

An electronic component designed to let current flow in only one direction, corresponding to the direction indicated by the arrow portion of its symbol.

Diode Testing

A diagnostic procedure performed on a disconnected diode using a voltmeter; one lead placement should read approximately $0.4\text{--}0.5\text{ volts}$ and the reversed placement should read "OL" (out of limits).

Absolute Pressure Sensor

A pressure sensor that measures pressure relative to a perfect vacuum.

Gauge Pressure Sensor

A pressure sensor that measures pressure relative to ambient atmospheric pressure, such as a tire pressure gauge.

Vacuum Pressure Sensor

A sensor that measures pressure below atmospheric pressure (negative gauge pressure) or low pressure relative to a perfect vacuum.

Differential Pressure Sensor

A sensor that measures the difference between two pressures connected to opposite sides of the device, commonly used to measure pressure drops across oil or air filters.

Piezoresistive Strain Gauge

A pressure measurement technology that utilizes the piezoresistive effect of strain gauges, often arranged in a Wheatstone bridge circuit, to detect strain caused by applied pressure.

Capacitive Pressure Sensor

A pressure sensor that uses a diaphragm and pressure cavity to create a variable capacitor for detecting strain from applied pressure.

Potentiometric Pressure Sensor

A sensor that measures strain from applied pressure through the physical movement of a wiper along a resistive mechanism.

Hall Effect Sensor

A transducer that varies its output voltage in response to a magnetic field, used for proximity switching, positioning, speed detection, and current sensing.

Crank Position Sensor

An electronic device in an internal combustion engine that monitors the position or rotational speed of the crankshaft to control ignition system timing and fuel injection.

Potentiometer

A three-terminal device acting as a sensing and voltage sending component that allows two current paths and taps a variable voltage signal off its sliding wiper.

Potentiometer Wire Functions

A three-wire configuration where wire "A" supplies operating voltage, wire "B" sends a variable voltage signal back to the controller, and wire "C" provides a return signal for self-testing.

Rheostat

A variable resistor used to control electrical power that utilizes only two terminals (the slider and one end terminal), unlike a potentiometer.

Float Level Sensor

A liquid level sensing unit connected to a potentiometer that slides a moving contact along a resistor to increase resistance as the fuel tank empties.

Capacitive Level Sensor

A liquid level sensor that applies a low-voltage, current-limited power source across separate electrodes matched to liquid conductivity, such as a water-in-fuel sensor.

Switch

An electrical device with ON/OFF capability only, displaying approximately $0.01\text{ ohms}$ when contacts are closed and a very high resistance reading ("OL") when open.

Relay

A magnetically activated switch with two separate circuits that allows a low-current circuit to control a higher-amperage circuit.

12-Volt Relay Coil Resistance

The normal resistance measured across coil terminals 1 and 2 on a 12-volt relay, which ranges between $75\text{--}85\text{ Ohms}$.