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Figure number 18 - Setting the function of the external temperature sensor
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RS485
Used to connect standard serial communication. RS-485 (as well as RS-422) is characterized
by a two-wire connection of units. These wires are marked with the letters A and B. In the
idle state, the voltage on wire A is lower than on wire B. The maximum length of the bus is
up to 1,200 m, the maximum number of nodes (i.e. devices transmitting and receiving data
along the line) is 32. When using repeaters, the number of nodes can be higher. The
maximum transmission speed is inversely proportional to the length of the line. The
transmission speed for short connections (up to 10 m) can be up to 10 Mb/s. When
communicating over longer distances, the line must be terminated on both sides with
termination resistors, or terminators. The purpose of "terminators" is to prevent signal
reflections from the ends of the line, they also help to increase the resistance of the line
against interfering signals. Ideally, the terminator should have a value of 110 Ω (so-called
image impedance), the resulting impedance of the line is then 55 Ω (110 Ω || 110 Ω). For
connection, use one of the two RS485 contacts, the other can subsequently be used to connect
another control panel in series (so-called cascade).
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