Limaco ULM-3D Series, Operating And Installation Manual

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6.2 PC connection via RS-6.2
The digital interface provides the user with access to the level transmitter readings
and allows the user to configure and diagnose the level transmitter. The digital in-
terface of level transmitter is implemented as a two-wire, serial RS-485 line. Mod-
bus RTU data exchange protocol. See protocol description in “Exchange protocol
for ULM sensors”. The advantages of using RS-485 include simple information
network building; the ability to transmit the readings of dozens of different sensors
over a single line, without loss of accuracy, over a distance of up to several kilome-
ters; the ability to configure the level transmitter from the workplace or integrate it
into a PLC-controlled industrial automation system (programmable logic controller,
PLC).
To connect the level transmitter to RS-485 line, terminals "A" and "B" are provided
on its terminal box. Each level transmitter has a unique Modbus address. The ad-
dress is set by an 8-bit DIP-switch, or determined by the internal device program, if
0-address is set.
A USB/RS-485 converter is used to connect the level transmitter to a computer via
a digital interface. Terminal "A" of the level transmitter is connected to terminal
"+", terminal "B" to terminal "–".
Fig. 6.3 Connecting the level transmitter using RS-485
Источник питания
Power supply
Use transducers with auto-detected transmission direction. A lot of standard devices
of this type are available, the most commonly used include: MOXA 1100 series
(uPort-1150i, uPort-1130), ADAM-4561, ICP DAS I-7561 series. Some converters
require setting data exchange parameters before the start. In this case install: trans-
mission rate – 9,600 bps, parity – even, data bits – 8, number of stop bits – 1 or 2.
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