Changing The Default Failsafe Direction; Procedure To Establish Failsafe Operation; Figure 16 - Locating The Failsafe And Write Protect Jumpers - Honeywell STT750 SmartLine User Manual

4.4.

Changing the Default Failsafe Direction

For HART the transmitters are shipped with a default failsafe direction of upscale. This means that the
Transmitter output will set the current output to upscale failsafe (maximum output) upon detection of
a critical status. The failsafe direction can be changed from upscale to downscale (minimum output)
by moving the top jumper located in the Electronic module.
The Transmitter electronics module interprets either signal as not-a-number and initiates its own
configured failsafe action for the control system.

4.4.1. Procedure to Establish Failsafe Operation

The failsafe direction display accessible via the Toolkit shows only the state of the
jumper as it correlates to analog Transmitter operation.
The integrated circuits in the Transmitter PWA are vunerable to damage by stray
static discharges when removed from the Electronics Housing. Minimize the possibility of
static discharge damage when handling the PWA as follows:
Do not touch terminals, connectors, component leads, or circuits when handling the PWA.
When removing or installing the PWA, handle it by its edges or bracket section only. If you
need to touch the PWA circuits, be sure you are grounded by staying in contact with a
grounded surface or by wearing a grounded wrist strap.
When the PWA is removed from the Transmitter, put it in an electrically conductive bag, or
wrap it in aluminum foil to protect it.
The following procedure outlines the steps for positioning the write protect and failsafe jumpers on
the electronics module. See
Figure 16 – Locating the Failsafe and Write Protect Jumpers
Page 28
Figure 16 for the locations of the failsafe and write protect jumpers.
STT750 Temperature Transmitter User's Manual
Revision 4