Tecfluid LU Series - Manual (Page 10)

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3.2 Power supply and analog output connection (models LU92X)
Models LU92X (LU921, LU923, LU921H) are 2-wire instruments. The connection is made
in the terminal block. The positive terminal of the power supply is connected to the
position + and the positive terminal of the load in the position -. The negative terminals of
the power supply and the load are connected together. The instrument works in a 2-wire
system, that is, the supply and signal line is the same. It is recommended to use a twisted
pair wiring or shielded cable to avoid interferences in the current loop.
3.3 Alarm outputs connection (only models LU9X)
Terminal
E Emitter
C Collector
The two available alarm outputs are optoisolated. The terminals are the collector and
emitter of an NPN bipolar transistor. In the case of using inductive loads, in order to
protect the transistor output, it is necessary to use free diodes (see next figure).