Measuring Ambient Temperature

Many designers want to measure the ambient temperature, not that of the PCB. To do this, they must prevent the heat sources on the PCB from affecting the temperature sensor by using the layout shown in figure 1:

Figure 1
Figure 1. Correct Layout for Measuring Ambient Temperature

Tips for ambient temperature measurement

  • Use a hash ground plane to reduce ground plane area, increasing thermal resistance.
  • Keep the temperature sensor as far from heat sources as possible.
  • Use a separate ground plane for the temperature sensor, and minimize connections to the main ground plane.
  • Use narrow ground connections, as this will increase thermal resistance.
  • Use solid ground plane under the main heat source and open the solder mask, minimizing the thermal resistance and maximizing the heat dissipation.

By following these tips, the temperature sensor will not be affected by the heat dissipated by the main heat source, and will accurately monitor ambient temperature.

Figure 2
Figure 2. Digital Temperature Sensor Accurately Tracks the Ambient Temperature


Donal McNamara