Terminal Resistance

What are requirements for terminal resistance at the ends of measuring line?

In constructing a measuring line with CAN or RS-485 interfaces, it’s necessary to set terminal resistance at its ends.

All the ZETLAB interface converters (except the ZET 7177 module) are equipped with built-in terminal resistances, thus the measuring line from interface converter side is equipped with terminal resistance.

There are third-party industrial devices (interface converters) with and without built-in terminal resistance. When using interface converters without built-in terminal resistance, it is necessary to set external terminal resistance. The measuring line side opposite to the side connected to the interface converter must be equipped with terminal resistance, value of which should be chosen based on the measuring line length:

  • line length up to 40 m — 120 Ohm;
  • line length 40 to 1000 m — 150…300 Ohm.