The air temperature sensor is used by the ECU to correct air density changes due to air temperature variation. This input can also be used for general purpose output controls like Intercooler fans or water spray pumps.

Operation
The resistance of the temperature sensor changes in relation to the temperature it senses. It has a negative temperature resistance co-efficiency, ( NTC). Each sensor has a preprogrammed curve to indicate its resistance to temperature. Note that the Spitronics ECU uses a 10K resistance NTC and this value is measured at 25°c .(See below for a sample of such a curve.)

Electronics sensors
Spitronics build and supply small sensors for customers to build into their own units. There are 2 sizes, both do the same work. Note: These sensors requires a pull-up resistor to enable a constant current through them. (See below a picture of what these sensors look like in their raw form.)

How to measure a sensor
Use a multi-meter set to the 20,000 ohm (20 K) range. With the sender unit at approximately 25°c, measure the resistance. It should be between 8000ohm and 12000ohm at 25°c.

Multiple Devices on One Sender Unit.
Do not share temperature sender units between two devices. Only one device may be coupled onto a sender unit at any one time. Both devices will excite the sensor with current which in turn will change the signal value and then both will display the wrong temperature. In such a case you may need to add an extra sensor for the Spitronics ECU. The only exception for this rule is when a data logging device is used that has no internal pull up resistor. Example: Race Technology DL1.

Sensor Location
The ideal sensor location is before the butterfly and after the intercooler if turbo charged. Mount away from fuel “stand-off” to avoid the sensor being cooled by the fuel vapor. Use a High Speed Air Temp sensor on turbo applications where the intercooler comes out as temperature varies quickly.