Quick Start Guide
25
March 2016
Figure 26. Field Mount Transmitter Analog Wiring - External Power
A. Power supply
Analog loop load limitations
Maximum loop resistance is determined by the voltage level of the external
power supply, as described in Figure 27.
Figure 27. Field Mount Transmitter Analog Loop Load Limitations
Wall mount transmitter
The analog output signal is a 4–20mA current loop. The loop can be powered
internally or externally via a hardware switch. The switch is set to internal power
when shipped from the factory.
For HART communication a minimum resistance of 250 ohms is required. It is
recommended to use individually shielded twisted pair cable. The minimum
conductor size is 0.51mm diameter (#24 AWG) for cable runs less than 5,000-feet
(1,500m) and 0.81mm diameter (#20 AWG) for longer distances.
Internal power
The 4–20mA analog signal is a 24VDC active output.
Maximum allowable loop resistance is 500 ohms.
R
max
= 31.25 (V
ps
– 10.8)
V
ps
= Power supply voltage (Volts)
R
max
= Maximum loop resistance (Ohms)
Power supply (Volts)
Load (Ohms)
Operating
region
600
10.8
30
400
200
0
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