The detection switch is a switch connected with other circuit elements to detect the parameters (such as current, voltage, etc.) of the element or circuit. The detection switch has induction function. It is often a variety of induction switches or proximity switches, and needs external power supply to work.

The detection switch has various output methods according to its purpose

1. Contact output type detect switches

Taking the contact of micro switch, limit switch and relay as the output switching element, and connecting with electromagnetic switch, small motor and electromagnetic device as the main purpose, it can carry out switching control of several amperes of current. When connecting with electronic control equipment, pay attention to vibration time and minimum load current.

2. Photoelectric coupling output type

The electrical insulation of the detection circuit is the same as that of the contact output type. Switch capable of controlling 10 ~ 50mA current.

3. DC 3-wire type

a. Voltage output type

When detecting, output voltage signal to load. The voltage output type is mainly manufactured for the purpose of connecting electronic control equipment composed of transistors or ICs such as electronic counters, contactless relays, etc.

b. Current output type

It can also be called open collector output type. When the output transistor operates, there are NPN type (current absorption) of suction current and PNP type (current source) of discharge current. If a small capacity power transistor is used in the output transistor, it can switch the current of 50 ~ 200mA, and directly drive the loads such as electromagnetic relay, electromagnetic valve, DC solenoid and display lamp.

4. DC 2-wire type

The proximity switch of this mode has two wires. Therefore, if attention is paid to the polarity during use, not only the use method can be the same as that of the mechanical limit switch, but also the wiring is simple, but the following conditions should be paid attention to.

(1) Even if the switch is closed, it is necessary to supply current to the detection circuit of the proximity switch. For this reason, a small amount of current flows in the load. This current is called leakage current. In case of leakage current, "leakage current" is generated at both ends of the load × Load is also the cause of initial failure. The occurrence time of initial failure varies according to different manufacturing methods, which can not be generalized. Generally, it occurs within 7 to 10 days after use.

(2) Accidental failure smd detector switches manufacturer

It includes faults caused by poor semiconductor components, broken wires, short circuits, insufficient capacity of resistors and capacitors, broken circuits of circuit boards, with solder, etc., but the incidence is very low. When the proximity switch often fails, it can be considered as the problem of service environment. Please consult the manufacturer.

(3) Load short circuit and wiring error

When the load is short circuited due to wrong wiring or live working, large current flows to the detection switch and the output circuit is burned. As a protection countermeasure outside the detection switch, the method of cutting off the fast short-circuit current can be used for protection through the fuse, which can not only protect the load short-circuit, but also protect the ground wire. However, due to the small residual capacity of the output transistor in the switch, the effect of 100% can not be achieved.

(4) Damage caused by interference wave

The damage caused by interference wave is formed slowly, so it is very common to have damage one month or two or three months after starting to use. Therefore, in case of damage during this period, the cause can be judged as interference wave. The instantaneous error action of the detection switch when the inductive load is opened and closed is caused by the interference wave.