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2-5
Installation
NOTE
Do not connect the power/signal wiring to the test terminals.
The voltage present on the power/signal leads may burn out the
reverse-polarity protection diode that is built in to the test terminal. If
the test terminals’ reverse polarity protection diode is burned out by the
power/signal wiring, the transmitter can still be operated by jumping
the current from one test terminal to the other.
Figure 2-4. Connecting a
Communicator to a Transmitter Loop.
Grounding
Transmitters are electrically isolated to 500 V ac rms. You can ground
the signal wiring at any single point, if desired. When using a grounded
thermocouple, the grounded junction serves as this point.
NOTE
Do not ground the signal wire at both ends.
Shielded Wire
Recommended grounding techniques for shielded wire usually call for a
single grounding point for each shielded wire to avoid grounding the
loop. The following two examples employ the single point grounding
technique:
Example 1
Connect the shield for the signal wiring to the shield for the sensor
wiring. Make sure that the two shields are tied together and
electrically isolated from the transmitter housing. Ground the shield
at the power supply end.
Example 2
Connect the shield for the sensor wiring to the ground terminal
inside of the terminal compartment of the transmitter housing. The
shield for the signal wiring should be cut and isolated from the
transmitter housing. This shield should be grounded only at the
power supply end. Never connect the shield for the signal wiring to
the ground terminal inside the transmitter housing.
Power/Signal
Terminals
The signal loop may be grounded at any
point or left ungrounded.
Power
Supply
250
V
≤
R
L
≤
1100
V
A HART communicator may be
connected at any termination
point in the signal loop. The
signal loop must have between
250 and 1100 ohms load for
communications.
3144
-0
0
00A
0
4
A