Switching circuit applied to contact resistance testing equipment of electromagnetic relay

Abstract

The invention discloses a switching circuit applied to contact resistance testing equipment of an electromagnetic relay. The switching circuit is characterized in that a contact changeover switching control circuit comprises a constant current source, a quadric-in-phase tristate buffer, a one-out-of-eight analog switch and a plurality of gating circuits consisting of optocouplers and Darlington transistors; the input end of the quadric-in-phase tristate buffer is connected with an IO (Input/Output) port of an MCU (Microprogrammed Control Unit), and the output end of the quadric-in-phase tristate buffer is connected with the control end of the one-out-of-eight analog switch; the input end of the one-out-of-eight analog switch is connected with a power supply, and eight output ends of the one-out-of-eight analog switch are respectively connected with the positive input end of the driving end of the optocoupler in one corresponding gating circuit; the negative end of the driving end of the optocoupler in one corresponding gating circuit is grounded; an output end collector of the one corresponding gating circuit is connected with a relay contact to be tested, and an output end emitter of the one corresponding gating circuit is connected with a control end of a Darlington transistor in one corresponding gating circuit; the input end of the Darlington transistor in one corresponding gating circuit is connected with a movable and static combination point of the electromagnetic relay to be tested; the GND end of the Darlington transistor of the corresponding gating circuit is connected with the negative end of the constant current source. According to the switching circuit disclosed by the invention, the contact resistance measurement reliability of the electromagnetic relay can be effectively improved.

Description

technical field [0001] The invention relates to a switching tube in electromagnetic relay testing equipment, in particular to a switching tube in multi-contact electromagnetic relay contact resistance testing equipment. Background technique [0002] Electromagnetic relay contacts undertake the task of switching current or carrying current for a long time, and its contact reliability is very important. In the parameter testing equipment of electromagnetic relays, the measurement of contact resistance is an indispensable testing item. Regarding the measurement of the contact resistance of electromagnetic relays, the national military standard GJB65B-99 requires the use of the Kelvin four-wire detection method. For this measurement method, a constant current source circuit and a contact resistance measurement circuit need to be provided during the measurement process. Electromagnetic relays usually have multiple contacts. The contact resistance of each contact needs to be measu...

AI Technical Summary

Problems solved by technology

Since the electromagnetic relay has many contacts to be tested, a large number of switching relays are required, which will still occupy a large area of ​​PCB or require external relays. The closing time and other performance of the relays will gradually deteriorate with the number of times of us

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