RS485 gas detectors use 4-core shielded wires, 2 power lines, and 2 signal lines. The transmission distance is relatively long, about 1-2Km; 4-20mA gas detectors use three-core wires, one power cord and one signal line. The transmission distance is relatively short, within 1 km.
Advantages of RS485 digital signal:
The signal is unified and the probability of failure is low. The RS485 digital signal system does not have such inconvenient factors at all. Data is transmitted in the same form on the data line, which enhances the reliability of the data. The wiring is simple and the workload is small. The obvious advantages of the bus system are less wiring, simple wiring, and low cost. For RS485 digital signal system, two signal lines and two power lines, the wiring is simple and convenient.
Disadvantages of RS485 system:
Signal delay: The data is brushed out one by one, which is especially obvious when there are a large number of probes. Power supply problem. All probes are powered centrally by the host. When there are a large number of probes and the power supply capacity of the host is insufficient, local power supply is required.
Advantages of 4-20mA analog signal system:
Data synchronization is good and power supply is unlimited. Compared with the bus system, each gas detector in the split-line system communicates with the controller independently, which can transmit the on-site conditions to the control part in a timely manner, so that the monitoring personnel can make timely and effective judgments, and the corresponding peripheral control equipment can be timely Effectively make corresponding control actions to avoid dangerous accidents.
Disadvantages of 4-20mA analog signal system:
The wiring is complicated. Signal interference is large. The amount of wiring is large, the workload is large, the wiring is complicated, the installation and construction are complicated, and the installation and material costs are high.
The signal outputs of fixed gas detector include the following:
1. 4-20mA analog signal output
The 4-20mA analog signal output gas detector is an instrument produced by our company that can continuously detect the concentration of toxic, harmful, flammable and explosive gases in the working environment. The detector detects gas concentration by natural diffusion and uses imported sensors with good sensitivity and excellent repeatability. Used in conjunction with the gas branch line control cabinet produced by our company, one control cabinet can be connected to multiple branch line probes. The output mode is two-wire or three-wire. The three-wire gas transmitter can output a set of relay switching signals. The transmission distance limit is 1000 meters. The two-wire gas transmitter uses a two-core shielded cable with a cross-section of 2×1.5mm2. The three-wire gas transmitter uses a three-core shielded cable of 3×1.5mm2 (the shielded wire can prevent on-site The dry resistance of other signals), the power supply of the gas probe in this connection method is provided by the gas control cabinet (24V DC)