Honeywell STT850 SMARTLINE, User Manual

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Revision 3 STT850
Temperature Transmitter User’s Manual
Page 11
For DE operation, add 2.0 V to these values. The Fieldbus transmitter operates from 9-32 V and does
not require a loop resistance.
Loop wiring is connected to the Transmitter by simply attaching the positive (+) and negative (–) loop
wires to the positive (+) and negative (–) terminals on the Transmitter terminal block in the
Electronics Housing. Connect the Loop Power wiring shield to earth ground only at the power supply
end.
Note that the Transmitter is not polarity-sensitive.
Figure 7
– Transmitter 9-Screw Terminal Board and Grounding Screw
As shown in
Figure 7 , each Transmitter has an internal terminal to connect it to earth ground.
Optionally, a ground terminal can be added to the outside of the Electronics Housing. Grounding the
Transmitter for proper operation is required, as doing so tends to minimize the possible effects of
noise on the output signal and affords protection against lightning and static discharge. An optional
lightning terminal block can be installed in place of the non-lightning terminal block for Transmitters
that will be installed in areas that are highly susceptible to lightning strikes. As noted above, the Loop
Power wiring shield should only be connected to earth ground at the power supply end.
Wiring must comply with local codes, regulations and ordinances. Grounding may be
required to meet various approval body certification, for example CE conformity. Refer to
Appendix A of this document for details.
Note: Terminal #3 is for loop test and is not applicable for Fieldbus option.
Terminal #4 is for Digital Output and is not applicable for Fieldbus option.
For HART and DE the Transmitter is designed to operate in a two-wire power/current loop with loop
resistance and power supply voltage within the operating range; see
Figure 6 . With an optional
remote meter, the voltage drop for this must be added to the basic power supply voltage requirements
to determine the required Transmitter voltage (V
XMTR
) and maximum loop resistance (R
LOOP MAX
).