Rosemount 8712, Reference Manual

Page: 17 / 212

Reference Manual
00809-0100-4664, Rev BA
January 2010
2-7
Rosemount 8712
Figure 2-3. Cable Preparation
Detail
Electrical Considerations
Before making any electrical connections to the Rosemount 8712, consider
the following standards and be sure to have the proper power supply, conduit,
and other accessories.
Transmitter Input Power
The 8712 transmitter is designed to be powered by 90-250 V AC, 50–60 Hz
or 12–42 V DC. The eight digit in the transmitter model number designates
the appropriate power supply requirement.
Supply Wire Temperature Rating
Use 12 to 18 AWG wire. For connections in ambient temperatures
exceeding 140 °F (60 °C), use wire rated to at least 194 °F (90 °C).
Disconnects
Connect the device through an external disconnect or circuit breaker.
Clearly label the disconnect or circuit breaker and locate it near the
transmitter.
Requirements for 90-250 V AC Power Supply
Wire the transmitter according to local electrical requirements for the supply
voltage. In addition, follow the supply wire and disconnect requirements on
page 2-9.
Requirements for 12-42 V DC Power Supply
Units powered with 12-42 V DC may draw up to 1 amp of current. As a result,
the input power wire must meet certain gauge requirements.
Figure 2-4 shows the surge current for each corresponding supply voltage.
For combinations not shown, you can calculate the maximum distance given
the supply current, the voltage of the source, and the minimum start-up
voltage of the transmitter, 12 V DC, using the following equation:
Use Table 2-1 and Table 2-2 to determine the maximum wire length allowable
for your power supply and maximum resistance.
NOTE
Dimensions are in
inches
(millimeters).
1.00
(26)
Cable Shield
Model Number Power Supply Requirement
2 12-42 V DC
1 90-250 V AC
Maximum Resis ce tan

Supply Voltage 12
–
VDC

1 amp

------------------------------------------------------------------------ =