Use of AD590 temperature sensor

Use of AD590 temperature sensor

The AD590 temperature sensor is an IC-based temperature sensor that converts temperature into current and is often seen in various 8051 textbooks. Its specifications are as follows:

1. For every 1°C increase in temperature, it will increase the output current by 1μA

2. Measurable range: -55℃ to 150℃

3. Supply voltage range: +4V to +30V

The pin diagram and component symbols of AD590 are shown in the figure below:

The output current value of AD590 is as follows:

Its output current is based on absolute temperature zero (-273℃). For every 1℃ increase, it will increase 1μA output current. Therefore, at room temperature of 25℃, its output current Iout=(273+25)=298μA.

AD590 basic application circuit:

Precautions:

1. The value of Vo is Io multiplied by 10K. At room temperature of 25°C, the output value is 10K×298μA=2.98V

2. When measuring Vo, do not separate any current, otherwise the measured value will be inaccurate.

AD590 actual application circuit:

circuit analysis:

1. The output current I of AD590 is (273+T)μA (T is Celsius temperature), so the measured voltage V is (273+T)μA×10K=(2.73+T/100)V. In order to measure the voltage and ensure that the output current I is not diverted, we use a voltage follower whose output voltage V2 is equal to the input voltage V.

2. Since the general power supply has noise after multiple devices, we use Zener diodes as voltage stabilizers and use variable resistors to divide the voltage. The output voltage V1 needs to be adjusted to 2.73V.

3. Next, we use a differential amplifier whose output Vo is (100K/10K)×(V2-V1)=T/10. If the temperature is 28℃ now, the output voltage is 2.8V, and the output voltage is connected to the AD converter, then the digital value output by the AD converter is linearly proportional to the Celsius temperature.