Control circuitry for thermoelectric environmental chamber

摘要

Circuitry for controlling the temperature of a thermoelectric environmental chamber includes a pair of digital switches for selecting any desired temperature between -10 degrees C. +79 degrees C., the digital slide switches selecting tap points of a group of series connected resistors forming a feedback loop of an operational amplifier. Three resistors connected in series with the output of the operational amplifier and the feedback resistors produce a plurality of voltages that represent upper and lower limits to tolerance range about the selected desired temperature. These voltages are compared by means of a plurality of comparators to a voltage produced in response to a solid state temperature sensor located in the thermal compartment of the environmental chamber. Decoding circuitry decodes the outputs of the comparators to produce signals which control switching devices that control the direction of current through a thermoelectric heat pumping device.