Sensors

Sensors measure physical properties, and convert their measurements into electrical signals to be captured by the data logger and used for running the vehicle, diagnosing the vehicle, verifying that the vehicle is running properly, and/or helping to tune the vehicle.

Sensor Types

Sensing location/movement of vehicle

These sensors are used to tell where the vehicle is, and how it is moving. Dataloggers often have some or more of these sensors built in. With these sensors, where they are mounted on the car may change how useful the data is. For instance, you may find that you want to mount them as close to the center of gravity as possible.

Accelerometer

Measures its acceleration in one or more axes. This may or may not be the actual acceleration of the vehicle, depending on how it's mounted.

Gyroscope

Measures its angular velocity (change in an angle over time) on one or more axes. Again, you'll probably want these axes to line up with those of the vehicle.

Magnetometer

Measures the strength and direction of the magnetic field. Useful for measuring the yaw of the vehicle.

IMU

Standing for Inertial Measurement Unit, it measures orientation, velocity, and acceleration in all three axes, utilizing accelerometers, gyroscopes, and magnetometers.

GPS Receivers

Obtains GPS data. This is usually used for logging the position of the car, so that you can see where the car is going and compare lines through corners.

Sensing Movement of a Single Component

Hall Effect Sensors

Detect the presence of a magnetic field. These are typically switches, that are either on or off (i.e., not analog). These are most commonly used to detect and measure rotation, e.g. of a gear. Unlike a VR sensor, they require an external magnetic force.

Variable Reluctance Sensors

Known also as VR sensors, they detect a change in the magnetic field. Unlike hall effect sensors, they do not require an external magnetic field, so many OEMs use them for cam and crank position sensors.

Potentiometers

Variable resistor ladders that measure movement. The can be used as driver controls (e.g., for adjusting radio volume), or in linear form for measuring shock travel (among other uses).

Rotary Position Sensors

These act as more accurate rotary potentiometers. Often they are contactless, meaning they last much longer and for many more cycles than potentiometers do. These are useful as pedal position sensors and steering angle sensors.

Knock Sensors

Sensors that detect engine knocking. These will bolt directly to the engine block, and will usually come with the engine.
there are a buncha different kinds of knock sensors - i'll try to get something sketched out here this week -simon

O2 Concentration Sensors

O2 sensors measure how much oxygen is in the exhaust. This allows you to figure out the air-fuel ratio of the engine. Narrowband O2 sensors can only tell you if you are rich, lean, or at the stoichiometric efficiency of the engine, whereas wideband O2 sensors tell you your exact air-fuel ratio with much more accuracy. Narrowband O2 sensors are usually used by the OEMs for troubleshooting catalytic converters, but most racecars use wideband O2 sensors to help tune the engine.

A wideband O2 sensor needs a wideband controller to connect to an ECU. Sometimes this is embedded inside the ECU, other times it has to be purchased separately.

Signal Types

Digital Sensors

Pulsed

Pulsed sensors send a series of digital pulses where the frequency of the pulses represents the measurement value. Commonly seen in shaft speed sensors.

PWM

PWM sensors vary the width of pulses at a fixed frequency to represent the measurement value. A simple analog filter can allow a PWM sensor to be approximated into an analog signal.

Serial

Some "smart" sensors transmit their measurement value(s) over a communication protocol such as CAN Bus, I²C, or SPI. This allows multiple values to be transmitted without additional wiring.

Some Common Applications

Driver Training

Sensor name	Use	Sensor type
GPS	Visualize and compare driving lines, visual aid for displaying data on an overlay of the course	GPS
Throttle position sensor (TPS)	Visualize and compare driver's throttle pedal control	Rotary position sensor or potentiometer
Accelerator pedal position sensor (APPS)	Visualize and compare driver's throttle pedal control	Rotary position sensor or potentiometer
Brake sensor	Visualize and compare driver's braking	Liquid pressure sensor, rotary position sensor or potentiometer
Steering angle sensor	Visualize and compare driver's steering	Rotary position sensor or potentiometer

Aerodynamics

Sensor name	Use	Sensor type
Air pressure sensor	Validating aero simulations
Air speed sensor	Calibrating downforce calculations for headwind	Pitot tube
Shock length sensor	Determining downforce at front vs. rear	Linear potentiometer

Brakes

Sensor name	Use	Sensor type
Brake pressure sensor (front and rear)	Validate braking system design, determine brake bias	Liquid pressure sensor
Brake light switch	Turn on brake light when brakes are applied	Liquid pressure switch
Brake rotor temperature sensor (front and rear)	Validate brake rotor design	IR temperature sensor

Chassis

Sensor name	Use	Sensor type
Strain gauges	Validating chassis stiffness	Strain gauge

Powertrain: Internal Combustion

Sensor name	Use	Sensor type
Cam position	Determine ignition/fuel timing	VR sensor
Crank position	Determine ignition/fuel timing and determine engine speed (aka RPM)	VR sensor
Accelerator pedal position sensor (APPS)	Required for ETC	Rotary position sensor or potentiometer
Throttle position sensor (TPS)	Required for ETC, helps determine how much fuel the engine needs	Rotary position sensor or potentiometer
Manifold/intake air pressure (MAP/IAP)	Determines how much fuel the engine needs	Air pressure sensor
Manifold/intake air temperature (MAT/IAT)	Calibrates AFR for the temperature of the air	Air temperature sensor
Coolant temperature (CLT)	Verify that the engine isn't about to blow up, tune engine for cold start	Liquid temperature sensor
Coolant pressure	Verify that the cooling system works, diagnosing problems	Liquid pressure sensor
Fuel pressure	Verify that the fuel system works, diagnosing problems	Liquid pressure sensor
Wideband O2	Tuning the car, diagnosing misfires (AFR will appear higher if a misfire is occurring)	O2 sensor
Gear sensor	Display what gear the transmission is to the driver	Rotary potentiometer?
Neutral switch	Tell the driver if they're in neutral or not	Switch
Vehicle speed sensor (at transmission output)	Verify differential performance, calculating what gear you're in	Hall effect sensor

Powertrain: Electric

Sensor name	Use	Sensor type
Motor position	Determines what angle the motor is at so the inverter can time the AC phases	Resolver, encoder, or hall effect sensor
Motor temperature	Make sure motor doesn't overheat	Temperature sensor
Coolant temperature (CLT)	Make sure motor and/or motor controller don't overheat	Liquid temperature sensor

Drivetrain

Sensor name	Use	Sensor type
Rear wheel speed sensors	Verify differential/torque vectoring performance, traction control	Hall effect, VR, inductive proximity sensor

Suspension

Sensor name	Use	Sensor type
Tire pressure	Verify tire performance, suspension tuning	Wireless air pressure sensor
Tire temperature	Verify tire performance, suspension tuning (even camber if multiple temperature readings per tire)	Surface or IR temperature sensor
Shock length sensor	Suspension tuning	Linear potentiometer
Strain gauges	Verify forces on suspension members	Strain gauge
IMU	Suspension tuning	IMU