temperature reading on a multimeter - 'How many volts above freezing is it?'

"How many volts above freezing is it?" A multimeter is the most common item of test equipment used by elec- tronic hobbyists. This is with good reason, considering how useful it is, but, of course, its abilities are fairly limited. Ask it about amps or volts or ohms and it is in its element. Broach the subject of degrees, however, and all you are likely to get is the multimetric equivalent of a blank stare. The versatility of a multimeter can easily be improved by adding the "temperature-to-voltage" converter shown here. The temperature sensor used in this circuit is an LM 335 which has a linear temperature characteristic of 10 mV/K. During manufacture this device is calibrated so that it gives an output of 2.73 V at 0°C (273 k). The LM 336 in the diagram is a very stable 2.5 V zener diode whose out- put is fed to IC2. The amplification of this CA 3040 can be varied temperature reading on a multimeter between 1.08 and 1.10 times, by means of P1, so this potentiometer must be adju...