Honeywell STT750 SmartLine - Wiring Variations; Loop Wiring Procedure

Revision 4 STT750 Temperature Transmitter User’s Manual Page 15
Transmitter loop parameters are as follows:
R
LOOP MAX
= maximum loop resistance (barriers plus wiring) that will allow proper Transmitter
operation and is calculated as R
LOOP MAX
= (V
SUPPLY MIN
– V
XMTR MIN
- V
SM
)  21.8 mA.
In this calculation:
V
XMTR MIN
= 11.8 V (HART) V
SM
= 2.3 V, remote meter
Note that V
SM
should only be considered if a remote meter will be connected to the transmitter.
The positive and negative loop wires are connected to the positive (+) and negative (–) terminals on
the terminal block in the Transmitter Electronics Housing.
Barriers can be installed per Honeywell’s instructions for Transmitters to be used in intrinsically safe
applications.
3.5.2. Wiring Variations
The above procedures are used to connect power to a Transmitter. For loop wiring, sensor wiring and
external wiring, detailed drawings are provided for Transmitter installation in non-intrinsically safe
areas and for intrinsically safe loops in hazardous area locations.
3.5.3. Loop Wiring Procedure
1. See Figure 12, above, for parts locations. Loosen the end cap lock using a 1.5 mm Allen wrench.
2. Remove the end cap cover from the terminal block end of the Electronics Housing.
3. Feed loop power leads through one end of the conduit entrances on either side of the
Electronics Housing. The Transmitter accepts up to 16 AWG wire.
4. Connect the positive loop power lead to the positive (+) terminal #1 and the negative loop
power lead to the negative (-) terminal #2. Note that the Transmitter is not polarity-sensitive.
5. Feed sensor input wires through the second housing conduit entry and connect wires per
Figure 12.
6. Replace the end cap, and secure it in place.