Is the Outside Temperature Displayed in Cars Accurate?
2 Answers
The outside temperature displayed on the car dashboard is not accurate. The temperature released by meteorological departments is measured based on the air circulating in a louvered box without direct sunlight, using a thermometer as the measuring tool. In contrast, the outdoor temperature displayed on the vehicle dashboard is measured by a temperature sensor. The outside temperature sensor is usually installed behind the engine intake grille, in front of the radiator. It measures the temperature of the air flowing through this area. There are three main reasons why the dashboard temperature is inaccurate: 1. Different air flow rates: Since the temperature sensor is installed behind the intake grille (i.e., the front grille), the temperature measured when the car is stationary versus when it is moving will differ due to varying air flow rates. 2. Influence of engine heat: The outside temperature sensor is installed near the front of the car, so it is affected by the heat from the engine. The air temperature near the engine and radiator is certainly higher than the ambient atmospheric temperature. 3. NTC thermistor: The principle of the outside temperature sensor generally involves using an NTC thermistor to measure temperature. NTC stands for negative temperature coefficient, meaning the resistance decreases as the temperature increases.
I've been driving for many years and noticed that the external temperature displayed by cars is often inaccurate, especially in urban areas or after parking. The sensor is usually installed near the front grille or bumper, designed to avoid engine heat interference, but engine operation or exhaust pipe heat can cause the reading to be a few degrees higher at idle. For example, in summer, after parking in a basement and starting the car, the display might show 35 degrees when it's actually only 30 degrees outside. At high speeds, because it's exposed to flowing air, the reading tends to be closer to the actual temperature. I often use it as a reference but don't fully trust it; in winter, when it shows near freezing, I'm cautious about frost risks and cross-check with the windshield or my phone's weather app. Keeping the sensor area clean is also important, as dirt can lead to misleading readings. Overall, it's a useful feature but has limitations, and drivers should be aware of its potential inaccuracies.
