3 and 1/2 digit digital thermometer using PTC thermistor

ICL7106/7107 is a dual-integrating A/D converter and 3-digit digital display driver. It is responsible for converting analog quantities into
digital signals. After further processing, it drives a 3.5-digit LED (ICL7106 drives LCD) digital tube to display the temperature data.
Character. ICL7106/7107 internally integrates oscillator, amplifier, comparator, counter, decoder, A/D converter
and other circuits. Use it to design a No. 3 digital display thermometer, which only requires a few peripheral components and is very simple to debug.
A 3÷-digit digital thermometer using PTC thermistor is shown in Figure 1-5.     The relationship between the numbers displayed by ICL7107 (lC2) and the input analog quantities is IV=IOOO Vl/VREF (IV is the displayed number, vl is the input voltage, VREF is the reference input voltage), VREF=VREF HI- VREF L0 , in this example VREF is set by RP2 (④ pin). In order to achieve the required accuracy and convenience of debugging, VREF is now set: lOOrriV ( determined by adjusting RP2 and RPl). At o°C, adjust RPi and RP2 to make vl(+)=273mV (corresponding to 273K =OC). In this way, when the temperature increases by loc every time, the voltage change on RT is processed by ICL7107 and the temperature is displayed digitally.     OC1. OC3 is the oscillation pin, and the frequency generated by the oscillation (, =1/2. 2R3Cl) provides the internal clock signal. REF HI and REF LO are the high and low inputs of the reference voltage respectively, which set the internal reference comparison potential; the @ and @ pins are the reference capacitors ; ⑤ and @ pins are the positive and negative analog inputs respectively, inputting the measured analog signal; ⑤-@ The pin is a buffer and integrating circuit     , and is connected to R and C externally.     ②． ⑧, ⑨~@, ⑤, ⑩~@, @ and ③ pins are the 7-segment signal output pins of the digital tube that drive units, tens and hundreds digits respectively , driving the digital tube to display the measured temperature number.