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## Design of temperature measuring circuit of AD590

Because the AD590 is a current output device, when designing a temperature measurement circuit, first convert the current into a voltage. When the temperature increases by 1K, the current of AD590 increases by 1μA. When the output current of the AD590 passes through a 10kΩ resistor, the voltage drop on this resistor is 10mV, which is converted to 10mV / K. In order to make this resistance accurate to 0.1%, a 9.6kΩ resistor and a 1kΩ precision potential can be used The devices are connected in series, and the precise 10kΩ resistance is obtained by adjusting the precision potentiometer. Figure 5 shows a current → voltage and absolute → Celsius temperature scale conversion circuit, in which the operational amplifier A1 is connected as a voltage follower to increase the input impedance of the signal. The function of operational amplifier A2 is to convert the absolute temperature scale into Celsius temperature scale, input a constant voltage (such as 1.365V) to the non-inverting input terminal of A2, and then adjust RP2 to amplify this voltage to 2.730V. In this way, the voltage between the output terminals of A1 and A2 is the voltage corresponding to the converted Celsius scale. Conversion circuit of current → voltage and absolute → Celsius temperature scale

Put AD590 into the ice-water mixed solution at 0 ℃, adjust RP1 to make the voltage of A1 output terminal 2.730V, adjust RP2 so that the output voltage of A2 is also 2.730V, so the voltage between the output terminals of A1 and A2: 2.730-2.730 = 0V, which corresponds to 0 ℃. 