See the picture below:
--------※------------※---------- ---※--------------
I hope the following suggestions will be helpful:
1. Use impedance matching and low attenuation RS485 dedicated bus cable (patent number: 2010?2?0559128.9, beware of counterfeiting) is more conducive to ensuring communication. The general recommendations are as follows:
Unarmored twisted pair shielded cable STP-120Ω (for RS485&CAN) one pair 18 AWG, the outer diameter of the cable is about 8.2mm. Suitable for indoor, pipeline and general industrial environments. When in use, one end of the shielding layer should be grounded!
Armored twisted pair shielded cable ASTP-120Ω (for RS485&CAN) one pair 18AWG, the outer diameter of the cable is about 12.3mm. It can be used in places with serious interference, frequent rodent infestations, and places with lightning protection and explosion-proof requirements. When in use, it is recommended that both ends of the armor layer be grounded and one end of the innermost shielding layer be grounded!
2. If the transmission distance exceeds 300 meters, a terminal resistor (usually 120Ω, connected in parallel) should be added. ?
3. Frequency converters, power cables, transformers, high-power motors, etc. are often accompanied by low-frequency interference, and this interference cannot be solved by cables shielded with high conductivity materials, including original ones. Imported cables. Only shielding layers made of high magnetic permeability materials (such as steel strips and steel wires) can effectively suppress low-frequency interference.
The most common method is to cover the cable with a steel pipe or directly use an armored cable made of high magnetic permeability material - ASTP-120Ω (for?RS485?&?CAN)?one?pair? 18?AWG?.
Lightning protection for outdoor laying cables is very important! The equivalent interference frequency of lightning is around 100k, which is also a low-frequency interference.
Article 6.3.1 of "GB50057-94 Design Code for Lightning Protection of Buildings": ...In the space that needs to be protected, when using shielded cables, the shielding layer should be at least at both ends. It is also advisable to make equipotential connections at the junction of lightning protection zones. When the system requires equipotential connections at only one end, two layers of shielding should be used, and the outer shielding should be processed according to the aforementioned requirements.
"GB?50217-2007 Cable Design Specification" also has similar statements. Please search "Industrial Automation Series Comprehensive Cable Solutions" to view the China Industrial Control Network. Welcome to communicate!