How Do External Car Thermometers Work?

External car thermometers, commonly used to measure the temperature outside a vehicle, work through a series of precise and accurate processes. This article will break down the workings of these thermometers, including the temperature sensors, placement, calibration, and additional features.

1. Temperature Sensors

External car thermometers typically use specialized temperature sensors to measure the ambient air temperature. The most common types of these sensors are thermistors and Resistance Temperature Detectors (RTDs).

Thermistors

Thermistors are temperature-sensitive resistors. When the temperature changes, the resistance of the thermistor changes. This change in resistance is detected by the thermometer, allowing it to calculate the external temperature accurately.

RTDs (Resistance Temperature Detectors)

Similar to thermistors, RTDs also change their resistance based on temperature. RTDs are generally more accurate and stable over a wider temperature range, making them the preferred choice in some high-precision applications. However, they are less common in automotive thermometers due to their cost and complexity.

2. Placement

The sensor is usually located in a strategic position where it can accurately measure the ambient air temperature. It is often mounted in the front of the vehicle, away from heat sources such as the engine or exhaust. This placement ensures that the sensor captures the true external temperature without interference from the car’s own heat.

3. Calibration and Display

The temperature reading from the sensor is sent to the car's onboard computer system, which calibrates the data based on the vehicle's specifications. The calibrated temperature is then displayed on the dashboard, often in a digital format for clear and easy reading by the driver.

4. Additional Features

Many external car thermometers offer additional features to enhance functionality and utility. These features include:

Ice Warning

This alerts the driver when temperatures drop to a level where ice may form on the road, ensuring safe driving conditions.

Integration with Climate Control Systems

This helps the vehicle's climate control system adjust air conditioning or heating based on outside conditions, providing a more comfortable driving environment.

Functioning of External Car Thermometers

The operation of an external car thermometer is similar to that of any other digital thermometer. When air temperature changes around the thermistor, its electrical conductivity changes accordingly. A computer chip and circuit detect these changes and convert them into a digital display. The embedded electronics are calibrated to account for any localized heating or cooling, ensuring a more accurate reading.

If you want to learn more about where these sensors are located in your car, you can refer to the car maintenance manual. The manual will often provide detailed information on the exact placement of the external car thermometer and other vehicle sensors.