Air temperature sensor

Types of Air Temperature Sensors

An air temperature sensor measures the temperature of the air using different principles and materials. Due to the different operating principles, they are available in various types:

• Thermocouples

  They consist of two wires made of different metals that generate a voltage when connected at a junction and subjected to different temperatures. The voltage is proportional to the temperature difference, allowing for temperature measurement. They are very versatile and suitable for measuring high temperatures in different environments.

• RTDs

  These are sensors that measure temperature using the resistance of a metal, typically platinum. As the temperature changes, the resistance of the platinum changes in a precise and repeatable way, allowing for accurate temperature measurements. They are known for their accuracy and stability, making them suitable for demanding applications.

• Thermistors

  They are temperature-sensitive resistors, usually made of ceramic materials, whose resistance changes significantly with temperature. They are commonly used in air temperature sensors because of their high sensitivity and precision over a limited temperature range. They are widely used in HVAC systems for accurate temperature control.

• Semiconductor Sensors

  These sensors use the temperature-dependent properties of semiconductor materials to measure temperature. They are often used in integrated circuits and are suitable for applications requiring temperature monitoring within electronic devices.

• Bimetallic Temperature Sensors

  This temperature sensor consists of two metals with different expansion rates bonded together. They are used in applications where simple and direct temperature measurements are required, such as in thermostats.

• Infrared Temperature Sensors

  These sensors measure the infrared radiation emitted by an object to determine its temperature without direct contact. They are suitable for applications requiring non-contact temperature measurements, such as monitoring moving parts in industrial settings.

• Capacitive Temperature Sensors

  These sensors use capacitors' temperature-dependent properties to measure temperature. They are often used in applications where precise temperature control is required, such as in medical devices.

Specification & Maintenance of Air Temperature Sensor

Specifications

• Measuring range

  The measuring range indicates the temperature limits that an air temperature sensor can measure. For instance, the measuring range of a resistance temperature detector can be from about -200 °C to 600 °C.

• Sensitivity

  Sensitivity in air temperature sensors indicates the smallest temperature change that the sensor can detect. It is usually measured in volts per degree Celsius (V/°C) or in ohms per degree Celsius (Ω/°C).

• Accuracy

  Accuracy refers to the degree of closeness between the measured air temperature and the actual temperature. The accuracy of an air temperature sensor is given as a percentage of the full scale of the sensor's output signal.

• Response time

  Response time is the time taken for an air temperature sensor's output signal to reach a specified percentage of the final value after a temperature step. The response time is usually expressed in seconds or minutes.

• Calibration

  Calibration is the process of adjusting the output signal of an air temperature sensor to match a known standard temperature. Calibration is usually done at the time of installation and periodically thereafter to maintain accuracy.

Maintenance

• Visual inspection

  Visual inspection involves checking the air temperature sensor and its surroundings for signs of damage, wear, or contamination. This includes looking for cracks, corrosion, dirt, dust, moisture, and other foreign materials that may affect the sensor's performance.

• Functional testing

  Functional testing is done to ensure that the air temperature sensor is working properly. The sensor's output signal is compared to a known standard temperature using a reference thermometer or another calibrated temperature sensor.

• Cleaning

  Cleaning is done to remove any contaminants that may affect the performance of the air temperature sensor. A soft cloth or brush and a mild detergent solution are used to clean the sensor's surface.

• Replacement

  Replacement is done when the air temperature sensor has reached the end of its useful life or is damaged beyond repair. A new sensor is installed according to the manufacturer's instructions and calibrated to match the system's requirements.

How to Choose Air Temperature Sensor

When choosing an air temperature sensor for a project, consider the following factors.

• Type of air temperature sensor: There are several types of air temperature sensors. Each type has its advantages and disadvantages. The user should select a type that will suit their needs. For example, thermocouples are reliable and have a fast response time. They are suitable for measuring quickly changing temperatures. On the other hand, RTD sensors are more accurate and stable.
• Temperature Range: Different temperature sensors have varying ranges. Therefore, buyers must choose sensors with an appropriate range for their applications. For example, an air temperature sensor with a high range should be used in industries that deal with high temperatures, such as the metal industry.
• Accuracy and precision: The air temperature sensor should give accurate and precise results. For applications that require highly accurate measurements, users should select sensors with a high degree of accuracy.
• Response time: The response time of a temperature sensor is how long it takes to measure a change in temperature. For applications where temperature changes quickly, a sensor with a fast response time is essential.
• Environmental conditions: The environmental conditions of the application affect the performance of the temperature sensor. Factors such as humidity, dust, and corrosive materials should be considered when selecting a sensor. Additionally, extreme weather conditions, such as high temperatures and strong winds, can affect the sensor's performance.
• Installation: Different air temperature sensors have different methods of installation. Some require professional installation, while others are easy to install. Additionally, the sensor should be installed in the correct position to get accurate results.
• Cost: The cost of the sensor should be within the budget. However, it's important to note that highly accurate sensors are expensive.
• Wiring: Air temperature sensors can be wired or wireless. Wired sensors are more reliable than wireless sensors. However, wired sensors are more difficult to install than wireless sensors.
• Sensor size: For applications with limited space, a small air temperature sensor is required.

How to DIY and Replace Air Temperature Sensor

A faulty air temperature sensor could be a DIY-able issue, but it requires a basic understanding of how to work with a multimeter and knowledge about the car's air temperature sensor system. Here's a basic guide to help DIYers out:

• Tools Needed

  Gather a basic set of tools: a screwdriver set, sockets and ratchets, a multimeter, possibly a scan tool for advanced diagnostics, and, sensor-safe cleaner. Also, have safety gear like gloves and safety glasses.

• Locate the Sensor

  Refer to the vehicle's service manual to find out the exact location of the air temperature sensor. Typically, it is found in the air intake duct, close to the engine control unit.

• Check the Sensor

  Use a multimeter to measure the sensor's resistance. Compare the readings to the specifications provided in the service manual. If they differ, the sensor may need replacement. Also, physically inspect the sensor for any visible damages and check the wirings for any loose connections or damages.

• Remove the Old Sensor

  Unplug the connector from the sensor. Use the appropriate tool to remove the sensor from its mounting location. Be careful not to drop any fasteners into the engine area.

• Install the New Sensor

  Coat the threads of the new sensor with a small amount of anti-seize compound (if recommended). Install the new sensor carefully into its mounting location. Do not overtighten, as this can cause damage. Plug the electrical connector into the new sensor.

• Test the System

  Start the vehicle's engine and allow it to reach the normal operating temperature. Use the scan tool or a temperature gauge to ensure the new sensor is functioning correctly and providing accurate temperature readings. Ensure the vehicle's temperature reading on the dashboard is normal.

• Reassemble

  Reassemble any parts or covers that were removed. Store all tools and dispose of any old parts according to local regulations.

Q and A

Q1: Where is the air temperature sensor located?

A1: Generally, the first air temperature sensor is located in the air box. The second one is located in the intake manifold.

Q2: What is the function of the air temperature sensor?

A2: The air temperature sensor measures the temperature of the air. After that, it sends this information to the engine control unit so that it can adjust the fuel mixture and other parameters.

Q3: How many air temperature sensors does a car have?

A3: Most cars have two. One measures the temperature of the air entering the engine. The second one measures the temperature of the air in the engine intake manifold.