1500
1250
1000
750
500
250
0
L
o
a
d
, ohms
with HART
communication
without HART
communication
12 18 24 30 36 42
545
ohms
1364
ohms
Power supply voltage, Vdc
HART option
Wiring
17
General
General Information
The 1066 is easy to wire. All wiring connections are located on the main circuit board. The front
panel is hinged at the bottom. The panel swings down for easy access to the wiring locations.
Digital Communication
HART and F
OUNDATION
fieldbus communications are available as ordering options for 1066. HART
units support Bell 202 digital communications over analog 4-20mA current output 1.
power Supply/Current loop – 1066 - hT
Power Supply and Load Requirements
Refer to Figure 4-1. The supply voltage must be at least 12.7 Vdc at the transmitter terminals.. The
power supply must be able to cover the voltage drop on the cable as well as the load resistor (250 Ω
minimum) required for HART communications. The maximum power supply voltage is 42.0 Vdc.
For intrinsically safe installations, the maximum power supply voltage is 30.0 Vdc. The graph shows
load and power supply requirements. The upper line is the power supply voltage needed to provide
12.7 Vdc at the transmitter terminals for a 22 mA current. The lower line is the power supply voltage
needed to provide 30 Vdc for a 22 mA current. The power supply must provide a surge current dur-
ing the first 80 milliseconds of startup. The maximum current is about 24 mA.
For digital communications, the load must be at least 250 ohms. To supply the 12.7 Vdc lift off
voltage at the transmitter, the power supply voltage must be at least 17.5 Vdc.
4.1
4.1.1
4.1.2
4.2
4.2.1
Section 4: Wiring
FIGuRE 4-1. load/power Supply Requirements
Instruction Manual
Section 4: Wiring
LIQ-MAN-1066
April 2017
