Two-wire proximity switch
The two-wire proximity switch is simple to install and the wiring is convenient and widely used, but it has the disadvantages of large residual voltage and leakage current.
DC three-wire type
The output type of the DC three-wire proximity switch is NPN and PNP. In the 70's, the vast majority of Japanese products were NPN output, and both NPN and PNP output models in Western Europe were available. PNP output proximity switches are generally used in PLCs or computers as control commands, and NPN output proximity switches are used to control DC relays. In practical applications, the output format of the control circuit is selected according to the characteristics of the control circuit.
Proximity switch selection and detection
Proximity switch selection
For different material samples and different detection distances, different types of proximity switches should be selected so that they have a high performance-to-price ratio in the system. Therefore, the following principles should be followed in the selection:
When the detection body is a metal material, a high-frequency oscillation proximity switch should be selected. This type of proximity switch is most sensitive to detection of iron-nickel and A3 steels.
For aluminum, brass and stainless steel samples, the detection sensitivity is low.
When the detector is non-metallic, such as wood, paper, plastic, glass, and water, capacitive proximity switches should be used.
When metal objects and non-metals are to be detected and controlled over long distances, photoelectric proximity switches or ultrasonic proximity switches should be used.