Freezer temperature monitor and alarm

An electronic instrument for measuring freezer temperature in the range of +40 to -40°C is described. The salient features of the instrument are remote display (digital and analogue versions with an accuracy of ± 0.1 and ± 0.5°C respectively) and provision for continuous record of temperature. Two types of sensors using thermistor and P. N. function of transistor were used for temperature sensing.