Honeywell STT750 SmartLine, Руководство пользователя

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Page 14 STT750
Temperature Transmitter User’s Manual
Revision 4
Figure 12
– Transmitter 9-Screw Terminal Board and Grounding Screw
As shown in
Figure 12 , 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.
Note: Pin 9 is not used.
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
For HART 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 11.
Figure 11 . 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
). Additional consideration is required when selecting intrinsic safety
barriers to ensure that they will supply at least minimum Transmitter voltage (V
XMTR MIN
), including
the required 250 ohms of resistance (typically within the barriers) needed for digital communications.