Discussion on the principle and structure of RF sensor with DC solid state relay

　　SSR can be divided into AC type and DC type according to the use of two categories, they are respectively in the AC or DC power supply to do the load switch, can not be mixed.

　　The following is an example of the AC type SSR to explain its working principle, Figure 1 is its working principle block diagram, Figure 1 of the components 1-4 constitute the main body of the AC SSR, from the whole point of view, SSR only two input (A and B) and two output (C and D), is a four-terminal device. When working, as long as certain control signals are added to A and B, the "on" and "off" between the two ends of C and D can be controlled to achieve the function of "switching", where the function of the coupling circuit is to provide A channel between the input/output terminals for the control signals input from A and B, but also to disconnect the (electrical) connection between the input and output terminals in the SSR. In order to prevent the DC solid state relay RF sensor, the principle, the structure of the output end of the input end of the influence, the coupling circuit with the element is "optocoupler", it is sensitive, high response speed, the input/output between the insulation (voltage) level is high; Since the input load is a light-emitting diode, it is easy for the input end of the SSR to match the input signal level, which can be directly connected to the computer output interface in use, that is, controlled by the logic level of "1" and "0". The function of the trigger circuit is to produce a trigger signal that meets the requirements and drives the switching circuit to work, but because the switching circuit does not add a special control circuit, it will produce radio frequency interference and pollute the grid with high order harmonics or spikes, for this purpose, a special "zero-crossing control circuit" is set up. The so-called "zero crossing" means that when the control signal is added and the AC voltage is zero, the SSR is on-state; Dc solid state relay RF sensor, principle, structure and when the control signal is disconnected, the SSR waits for the junction of the positive and negative half cycle of the alternating current (zero potential) before the SSR is off. This design can prevent the interference of high order harmonics and the pollution of the power grid. The absorption circuit is designed to prevent the impact and interference (or even misoperation) of the bidirectional thyristor tube of the switching device from the peak and surge (voltage) coming from the power supply. The DC solid-state relay RF sensor, principle, structure is generally used with "R-C" series absorption circuit or nonlinear resistor (varistor).

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