Development of multichannel insulation resistance automatic measurement device for load side of combination switch

In order to improve the safety of explosion-proof combination switch, the insulation performance of the load side need to automatically detect. A reliable combination switch load side multi-channel insulation automatic measuring device is designed. The device adopts the modular design thinking, including PC, power supply module, high pressure detection circuit, the central processor unit（CPU） Atmega16 and Atmega64. PC is used to send and receive instruction, display combination switch state and testing data, and so on. Power supply module is mainly used to convert alternating current（AC） power into 5 V for the use of single-chip microcomputer and 12 V for high voltage testing circuit. High voltage detection circuit convert DC 12 V to DC 2 500 V which load on the load side to measure insulation resistance. The CPU Atmega16 is mainly used to detect 12 channel atresia state and drive relay opening and closing load circuit. The CPU Atmega64 is mainly used to receive PC’s instructions, determine whether have test conditions, control the opening and closing of atresia light and detect light, collect and process the testing numerical value and then sent to PC. Two CPU achieve real-time communication through the RXD/TXD. The CPU Atmega64 achieve real-time communication with PC adopting RS 485 technology, and communication protocols adopt industry standard Modbus protocol. Engineering practices show that the device can rapidly and accurately detect combination switch load side multi-channel insulation resistance, greatly improve the work efficiency.