61F-03B

The 61F-03B is a reliable and accurate castellated PC board mounted temperature control switch which can be mounted by wave soldering process. It is designed for controlling temperatures ranging from -20 to +125°C (-4 to +257°F). It is used in a wide range of products including air conditioners, water heaters, ovens, freezers, and hot water pipes. The 61F-03B has three main components: a thermal diode, a thermistor, and a switch.

The dual common emitter NPN transistors are combined with a temperature sensitive resistor to form the thermal diode. The thermal diode is mounted on the printed circuit board and is connected to the thermistor. The thermistor acts as a current-carrying resistor whose resistance is dependent on temperature. As the ambient temperature increases, the resistance of the thermistor increases and the voltage across it drops.

The thermistor is also connected to the control circuit, which contains an amplifier and comparator circuit. When the thermistor senses a temperature above its set point, the amplifier increases the gain and causes the comparator to switch off. This turns off the relay contacts, cutting off power to the load.

The switch is mounted on a PC board and is connected to the comparator, thermal diode, and thermistor. The switch is designed to reset automatically when the temperature drops below its set point. The reset is accomplished by passing a small current through the switch, thus, manipulating its operational state.

The 61F-03B provides an economical and reliable way of controlling temperature. It is simple to install and relatively easy to maintain. The application field for the 61F-03B is broad and includes most consumer and industrial products with temperature control requirements. Its working principle is based on the thermal characteristics of an NPN transistor, a thermistor, and a switch.