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This is the Simple Temperature sensor and DVM interface Circuit Diagram. The DVM gives a direct indication of the temperature of the sensor in degrees Centigrade. The temperature sensor IC1 gives a nominal 1 µ per degree Kelvin which is converted to 10 mV per degree Kelvin by Rl and VR1. IC2 is a micropower, low input drift op amp with internal voltage reference and amplifier.   Simple Temperature sensor and DVM interface Circuit Diagram The main op amp in IC1 is connected as a voltage follower to buffer the sensor voltage at Rl. The second amplifier in IC1 is used to amplify the .2 V internal reference up to 2.73 V in order to offset the 273 degrees below 0°C.The output voltage of the unit is the differential output of the two op amps and is thus equal to 0.01 V per °C. Sourced By: Circuitsproject

The majority of hand-held digital volt meters use an LCD screen and are powered from a nine volt battery. Inside is most probably an ICL7106 chip (or something compatible). This takes care of measuring the input and driving the LCD. This IC is very popular and can be found in other laboratory and homebrew equipment where it offers a simple solution for both measuring current/voltage and driving the display. So far so good, there is how-ever one feature of this device which needs careful consideration. The power supply to the chip (both the positive and negative connection) must not have any direct connection to either of the two measuring input terminals. It requires floating supplies. This is not a problem for battery powered equipment but needs more thought when the ICL7106 is fitted into mains powered equipment. Ground-free DVM Module Supply from 5 V Circuit Diagram : The simplest, most expensive solution is to use two independent power supplies in the equipment. A battery could...