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Installation Notes on Ametek UHP 4-20 mA Transmitter (continued)
Wiring Notes: 4-20 mA. pigtail cable style
1. Hookup: The 4-20 mA transmitter utilizes a 2 wire system. Current flowing from a
power supply into the red lead is used to power the transmitter. Current flowing out
of the black lead may be connected to a 4-20 mA input of a loop indicator, for
example, or across a loop resistor. The return from the loop indicator or loop resistor
should be tied to the negative connection of the power supply.
understand the voltage drop of any loop device added in series with the current flow.
For example, many loop indicators or PLC's may take up to 5 Vdc each to operate (at
full scale current of 20 mA.). The transmitter should have at least 12 Vdc across the
red and black leads at all times. Thus in this example, with the transmitter needing 12
Vdc to operate and the loop indicator and PLC each requiring 5 Vdc, the power
supply should be set above 22 Vdc. A 24 Vdc supply is often used when operating
multiple loop devices.
2. Grounding and Shielding: The green lead is a connection to the transmitter case and
may be used as required to provide continuity to the case. For use in high EMI fields,
the user may wish to tie the additional drain wire (this is also tied internally to the
transmitter case) to the gas cabinet case or system earth ground to provide optimal
EMI shielding. With some installations, it may not be desirable to tie the green wire
or drain wire to the gas cabinet case or system earth. Ground loops may prevent this
type of hookup so caution is advised.
White Wire: The white wire is not used in a 4-20 mA configuration.
Wire Color
Red
Black
White
Green
Shield
pg. 2-3
Signal/Exc.
+
-
Not Connected
Case
Case
It is important to
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