Three Button Operation With No Display Installed; Zero Adjustment; Span Adjustment; Changing The Default Failsafe Direction - Honeywell ST 700 User Manual

4.3 Three Button Operation with no Display Installed

When there is no Display installed, the buttons can be used to perform a Zero or Span adjustment of
the Transmitter. Caution should be taken to insure these adjustments are only made when the correct
input pressures are applied.

4.3.1 Zero Adjustment

This adjustment is the same as performing a Set LRV using the Display.
1. Connect a current meter or voltmeter as shown in Figure 15 to monitor the PV output of the
Transmitter.
2. Using an accurate pressure source, apply pressure equivalent to the Transmitter LRV.
3. Press the Down (
4. Verify that the output is now 4 mA.

4.3.2 Span Adjustment

This adjustment is the same as performing a Set URV using the Display.
1. Connect a current meter or voltmeter as shown in Figure 15 to monitor the PV output of the
Transmitter.
2. Using an accurate pressure source, apply pressure equivalent to the desired Upper Range
Value of the transmitter.
3. Press the Down (
4. Verify that the PV output is now 20 mA.
You can also use the MCT 202 Toolkit to make any adjustments to an ST 700
SmartLine Pressure Transmitter. Alternately, certain adjustments are possible
through an Experion Station or Universal Station, if the ST 700 is digitally
integrated with either of these stations.

4.4 Changing the Default Failsafe Direction

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. You can change the direction from upscale failsafe to downscale failsafe (minimum output) by
moving the top jumper located in the Electronics module.

4.4.1 DE and Analog Differences

Failsafe operation is somewhat different between DE and analog operation:
•
Analog operation – Upscale failsafe drives the Transmitter output to 21.8 mA. Downscale
failsafe drives the Transmitter output to 3.8 mA.
•
DE operation – Upscale failsafe causes the Transmitter to generate a + infinity digital
signal. Downscale failsafe causes the Transmitter to generate a – infinity digital signal.
The Transmitter electronics module interprets either signal as not-a-number and initiates its own
configured failsafe action for the control system.
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↓
) and Zero ( ↑ ) buttons together to set the Zero.
↓
) and Span ( ) buttons together to set the span.
ST 700 SmartLine Pressure Transmitters User's Manual Revision 1.0