Vaisala HMP228 - Manual (Page 17)

HMP228
M210282en-A Operating Manual
11
Power supply 24 VDC
24 VAC (see Chapter 2.3.2)
with power supply module 115/230 VAC
Output signals 0...20 mA
4...20 mA
0...1 V
0...5 V
0...10 V
Power supply ground (-) is connected to the housing with parallel connection
of 15 nF capacitor and 300 k
Ω
resistor.
See Appendix 3 on how to connect the power supply module to the
transmitter.
2.3.2 Connection to an AC supply
The HMP228 transmitter can also be connected to an AC supply without an
external rectifier. However, when more than one transmitter is connected for
example to one 24 VAC transformer, a common loop is formed and there is an
increased risk of a short-circuit. To avoid this, always use separate floating
supply for each transmitter (see Figure 2.3.2 A). However, if several
transmitters have to share one transformer, the phase (
∼
) must always be
connected to + connector in each transmitter (see Figure 2.3.2 B).
24 VAC
Controller
shared
common
24 VAC
24 VAC
HMP228 transmitter Controller
B) COMMON LOOP FORMED - NOT RECOMMENDED!
A) NO COMMON LOOP FORMED - RECOMMENDED
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HMP228 transmitter
HMP228 transmitter
HMP228 transmitter
Figure 2.3.2 Connecting the transmitter to an AC supply