Instrument signal wire

When selecting a product, it comes down to technical requirements: whether shielding against interference is necessary, whether copper wire material is required, whether it should be a hard wire or a flexible one, how many wires and cores are needed, and what the cross-sectional area of the wire should be, etc.

Twisted pair shielding is sufficient; it’s convenient to use armored cables for the connection from the field meter to the junction box.

For transmitting analog signals such as 4-20mA, RVVP, KVVP, KVVRP, and KYJVP can be used as options； If the instrument panel has digital interfaces such as RS485, a twisted-pair shielded cable, such as a fieldbus cable, can be used. ---------------------------------------------------------------------- The general-purpose field bus series of cables consists of twisted-shielded cables with a characteristic impedance of 120Ω, which are widely used in buses such as RS485/422 and CANBUS. There are many different specifications for these cables; please provide details such as the cable installation environment, communication speed, and maximum transmission distance without repeaters. We will then recommend the most suitable product based on these specific conditions. The following is generally recommended: standard twisted-shielded cable STP-120Ω (for RS485 & CAN), one pair with 20 AWG wire; the outer diameter of the cable is around 7.7 mm, with a blue jacket. Suitable for indoor, pipeline, and general industrial environments. When in use, one end of the shielding layer must be grounded! Standard twisted-shielded cable STP-120Ω (for RS485 & CAN), one pair, 18 AWG; outer diameter of the cable is about 8.2 mm, with a gray jacket. Suitable for indoor, pipeline, and general industrial environments. When in use, one end of the shielding layer must be grounded! Armored twisted pair shielded cable ASTP-120Ω (for RS485 & CAN), one pair 18 AWG; outer diameter of the cable is about 12.3 mm, with a black jacket. It can be used in areas with severe interference, frequent rodent problems, as well as those with requirements for lightning protection and explosion prevention. When in use, it is recommended to ground both ends of the armor layer, and ground one end of the innermost shielding layer!

One more thing to keep in mind: the 100-meter uniformity (that is, the difference in resistance per 100 meters between every pair of cores in a multi-core wire). This significantly affects the accuracy of signal transmission, especially when the cable is long; if the uniformity over a distance of 100 meters is poor, the measurement results will be greatly compromised, affecting accuracy. Many manufacturers and customers are not very aware of this parameter or do not pay it much attention, but it is what distinguishes high-end from low-end products

What is mentioned on the 5th floor concerns the issue of unbalanced resistance, which is extremely important for communication cables!