RS485 interface sensor wiring method

RS485 is a differential serial communication protocol commonly used in industrial communication, featuring long transmission distance, strong anti-jamming capability, multi-station capability, etc., so it is widely used in various automation control systems. In RS485 communication, the correct wiring is essential to ensure the stability and reliability of communication.

First of all, we need to understand the RS485 interface, RS485 interface is usually two-wire or four-wire wiring. Two-wire wiring system, the data signal is transmitted through a pair of twisted-pair wires, including A and B. A line for the positive pole, B line for the negative pole, through the differential signal for data transmission. The four-wire wiring system consists of two pairs of twisted-pair wires, which are used for sending and receiving data respectively, in which the A wire of the transmitting end is connected to the A wire of the receiving end, and the B wire of the transmitting end is connected to the B wire of the receiving end. Then it is the RS485 interface that is noted, where T/R+ stands for A+ and T/R stands for B.

RS485 interface sensor wiring method

RS485 sensor wiring usually includes power, signal and earth wires. Here are the basic wiring steps and precautions:

RS485 sensor wiring steps:

1. Power cord connection:

Connect the sensor's power cord to a power source. The power requirements of the sensor should be determined according to the sensor specifications.

2. Signal line connection:

Connect the signal line of the sensor to the corresponding position on the RS485 bus.

For the Transmitter, connect to one of the bus lines (usually line A);

For the Receiver, connect to another wire (usually line B) of the bus.

3. ground connection:

Connect the sensor's earth wire to the bus's ground (GND).

Make sure that all earth wires are connected to the same ground reference point to avoid interference caused by different ground potentials.

 Wiring Precautions:

 Electrical Characteristics: Ensure that the electrical characteristics (e.g. voltage, current) of the sensor are compatible with the RS485 bus.

 Anti-interference: It may be necessary to add an isolator or optoisolator between the sensor and the RTU to improve the system's anti-interference and safety.

 Impedance matching: In long-distance transmission or high-noise environments, it may be necessary to add termination resistors to match the impedance of the bus to reduce signal reflection and loss.

 Wiring length: Comply with the maximum cable length specified in the RS485 standard, usually not exceeding 1200 metres.

 Shielding: If there is strong electromagnetic interference in the environment, it is recommended to use shielded cables to reduce the interference.

 Terminating resistors: Add terminating resistors at both ends of the bus to prevent signals from reflecting during transmission.

 Surge Protection: Add a surge protector between the power and signal lines to protect the sensor from power fluctuations and surges.

Wiring Example:

Power Positive > Sensor Power Positive (+)

Power negative > Sensor power negative (-)

Wire A > Sensor signal wire (transmitter)

Wire B > Sensor signal wire (receive side)

GND > sensor ground

Please follow the specific sensor and bus device instructions to ensure correct wiring. Incorrect wiring may result in communication failures or damage to the device.