Vaisala WAT12 - Manual (Page 23)

Chapter 3 __________________________________________________ Installation
VAISALA__________________________________________________________21
0206-052
Figure 14 Long Distance Wiring with Four Wires
Powering
The WAT12 transmitter accepts a wide range of input
power, from 12 to 28 VDC. When the 5 mA loop current is
selected, the total current consumption is less than 40 mA
including the sensors and the loop current. The low current
consumption enables to remotely supply the operating
power from a distance of several kilometers, even through
private or leased telephone lines.
The maximum power line resistance depends on the supply
voltage and the loop current selection. For an example with
an 24 VDC power supply, refer to and to Figure 11 on page
19.
Table 5 Power Line Resistance with an 24 VDC
Power Supply
Loop Current, mA Power Line Resistance, Ω Ω Ω Ω
5 360
10 310
20 250
For other powering options, refer to Figure 12 on page 20,
Figure 13 on page 20, and Figure 14 above.