Two-wire temperature measurement-frequency converter

Converting the temperature measurement signal into frequency output
can facilitate the interface with digital circuits and can also display the temperature in digital
form. It has the advantages of intuitive, convenient reading and
accurate display.
The circuit as shown in the figure converts the temperature measurement signal into frequency and can be easily connected to CMOS and TTL circuits.
    The temperature measurement element is the integrated temperature sensor AD592. The output voltage is proportional to the temperature, and the change rate is 1pLV/K. Since
the change of the AD592 is measured according to the temperature K (Kelvin), if the temperature measurement is to be measured in degrees Celsius,
an AD589 (AD589) needs to be added. L 2V reference voltage source), Ri-R3 is corrected, and R3 is adjusted so that the output temperature frequency changes to
10Hz/oC. The output signal is driven by v and can be directly interfaced with TTL and CMOS circuits.