7 Basic Types of Temperature Measuring Sensors

Q: What does the intake air temperature (IAT) sensor do? A: The IAT sensor plays an important part in your engine’s efficiency. It is responsible for detecting the temperature of the air that is coming into the engine so that it can relay the data to the car’s main computer.

Typically, the temperature readings should be 10 degrees more or less than the vehicle’s ambient temperature, depending on the outside temperature and the engine’s temperature. If the readings are not realistic, there could be a problem with your IAT sensor or the wirings to it.

• Testing the Engine Coolant Temperature by Visual Inspection.
• Testing the ECT Using a Multimeter.
• Testing the ECT Sensor Using a Scan Tool.

• Thermocouples. Thermocouples are voltage devices that indicate temperature measurement with a change in voltage.
• Resistive Temperature Measuring Devices. Resistive temperature measuring devices also are electrical.
• Infrared Sensors.
• Bimetallic Devices.
• Thermometers.
• Change-of-state Sensors.
• Silicon Diode.

An NTC thermistor is able to achieve the highest accuracy of the basic sensor types within the -50 °C to 250 °C range. Accuracy ranges from 0.05 to 1.5 with high long-term stability, depending upon the type of sensor and packaging used. NTC thermistors also offer superior responsiveness, on the order 0.12 to 10 s.

Several factors must be considered when selecting the type of sensor to be used in a specific application: temperature range, accuracy, response time, stability, linearity, and sensitivity. These are summarized in Table 1.

How do temperature sensors work? They are devices to measure temperature readings through electrical signals. The sensor is made up of two metals, which generate electrical voltage or resistance once it notices a change in temperature. Temperature is the most common physical measurement type in industrial applications.

A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer or the pyrometric sensor in an infrared thermometer) in which some change occurs with a change in temperature; and (2) some means of converting this change into a numerical value (e.g. the visible scale …

Temperature sensors are used in diverse applications such as food processing, HVAC environmental control, medical devices, chemical handling and automotive under the hood monitoring (e.g., coolant, air intake, cylinder head temperatures, etc.).

Among the contact temperature sensors are thermocouples and thermistors. A thermocouple is comprised of two conductors, each made of a different type of metal, that are joined at an end to form a junction. When the junction is exposed to heat, a voltage is generated that directly corresponds to the temperature input.

The thermostat can directly control your boiler, in that if the temperature is too low in the room, it can call for heat using the wiring in your house. The temperature sensor just measures the temperature and reports it back.

What Signs May Signal Your Coolant Temperature Sensor May Be Failing?

1. Poor Fuel Economy.
2. Irregular Temperature Readings.
3. Black Smoke from Your Exhaust.
4. Your Engine is Overheating.
5. Your Check Engine Light is On.

Thermostats use different types of sensors to measure the temperature. In one form, the mechanical thermostat, a bimetallic strip in the form of a coil directly operates electrical contacts that control the heating or cooling source.

Faulty readings from the coolant temperature sensor can cause your car’s engine to miscalculate the fuel to air mixture within the engine. If the amount of black smoke emitting from your car is excessive, then you should not drive your car and you should tow your vehicle to a mechanic.

The average cost for engine coolant temperature sensor replacement is between $123 and $158. Labor costs are estimated between $82 and $104 while parts are priced between $41 and $54.

To clean the sensor use a heavy duty Scotch Bright (green type) cleaning pad. I cut the sheets into about 1.5″ x 1.5″ squares; it make it easier to clean with them. Use isopropyl alcohol as the cleaning agent, and wipe with a paper towel.

The sensor will not cause a no start. It could cause a hard start and a rich or lean condition only.

Your Ideal Thermostat Placement Central location. On an interior wall. Mounted 52-60 inches above the floor. Away from air vents, doors, windows, and skylights.

A faulty ECT sensor can send a false signal to the onboard computer, resulting in an incorrect air-fuel mixture. For example, a faulty sensor can send a signal indicating the engine is cold when it is not, and more fuel will heat the engine quickly.

1. Step 1 – Locate Coolant Temperature Sensor. The coolant temperature sensor is located on the engine block under the hood.
2. Step 2 – Connect Digital Volt-Ohm Meter.
3. Step 3 – Check Readings.
4. Step 4 – Check With Cold Sensor.
5. Step 5 – Replace Defective Coolant Temperature Sensor.

The engine coolant temperature sensor is temperature-variable resistor, which usually has a negative temperature coefficient. It is a two-wire thermistor immersed in coolant and measures its temperature.

Often, the engine coolant temperature sensor must be replaced at about 100,000 miles. If you don’t properly maintain the engine cooling system, the sensor could fail much earlier.

The actual process of replacing the coolant temperature sensor is extremely simple. However, the difficult work comes in the preparation of the cooling system – both before and after. Tip: This job should only be completed when the engine is cold and has not been running for a minimum of one hour.

Let’s Get Started

1. Release the Cooling System Pressure. Locate and slowly remove the cooling system pressure cap to relieve the system of any residual pressure.
2. Locate the Coolant Sensor.
3. Remove the Electrical Connector.
4. Remove the Coolant Sensor.
5. Install the New Coolant Temperature Sensor.
6. Refill the Cooling System.

Open the radiator valve and drain about two to three quarts of coolant. You only need to remove enough to drop the level below the sensor. Then close the drain valve. This will minimize coolant waste when you remove the sensor.