To the problem of multiple dry-reed relays electromagnetic interference in application circuits, we present an effective method to reduce the electromagnetic interference in this paper. The method is alternating permutation matrix of dry-reed relays. The paper describes the cause of electromagnetic interference of dry-reed relays. Using the offset of electric polarity alternation principle, we put forward the method for reducing electromagnetic interference. The method is applied to a multi-functional physiotherapy instrument. By experiments, experimental result shows that the degree of electromagnetic interference is reduced along with the increase in the number of dry-reed relays.
