What is the use of PROFIBUS Terminator? -Solutions - Huaqiang Electronic Network

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Q: What is the use of PROFIBUSTerminator? When is it used?

Question added: I said this thing, not our general DP connection port, but a special terminal, the code is: 6ES7972-0DA00-0AA0.
According to the instructions of the people and the situation on the spot, there should be no DP substation on this profibus bus, only turned into 485, for the activation of the signal, the terminal is used.

A: The terminating resistor has two functions:
1. Maintain an idle potential of approximately 1.1V.
2. Ensure that the terminal impedance is consistent with the line impedance to avoid signal reflection.
The effect of the bus terminal when the station is powered down:
1. The loss of two 390 ohm resistors causes the bus idle potential to drop to about 5×110/390+220+390=0.62V. In this case, the bus is susceptible to interference.
2. The terminal impedance is inconsistent with the line impedance. The line impedance is 150 ohms and the terminal impedance is only 110 ohms. Theoretically, a reflected wave with an opposite polarity of about 0.15 times incident wave can be generated.
The terminating resistor should be added at the end of the PROFIBUSDP network, just like the ordinary resistor, but the three resistors are connected in series, respectively 390Ω220Ω390Ω, the DP bus is connected to the 220Ω side, and the other ends are connected to the power supply, followed by the DP 5, 3, 8 6, 5, 6 is a 5V power supply, and the 220Ω ends are about 1V.

The position of the terminal resistance dial code is the position of the device at both ends (that is, the device that only enters the line) hits the "ON" position, and the device in the middle reaches the position of "OFF".