Servo Auto Test - Honeywell 854 ATG Series Instruction Manual

4.8 Servo Auto Test

The Servo Auto Test (SAT hereafter) is an automatic safety related function meant to reduce the small risk of
tank overfill caused by a failing servo gauge. Immediate after the gauge detects that tank loading has finished
a SAT is executed to rule out (or detect) that the gauge is unable to measure the product level due to some
failure (e.g. blockage of displacer). The gauge will raise the displacer over a programmable distance (item
SH). If the movement is not completed within the expected time, the gauge will retry. If this second try also
fails, a third and final attempt is made. Should even the third try fail, the gauge will update the display by
removing the measurement unit and display the fill mode. After that the gauge will go into General Fail mode
and item ES is set to the value 607 (SAT failed for three consecutive attempts). From this moment on the
gauge will respond only to status requests and the reset command (item RS).
The SAT will not only be executed immediately after tank loading has apparently stopped, but also at regular
intervals configurable through item SI.
The SAT can also be performed manually by entering the command PQ.
The default behaviour of the SAT can be influenced by means of a number of configuration items.
Item Name
SE SAT enable
SH SAT raise height
SI SAT interval time
SY
SAT invalidate display and level
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Description
When set to 'E' (enabled) a SAT will be started roughly 1 minute after
tank loading has apparently stopped. Furthermore SATs will be
executed at regular intervals. When set to 'D' (disabled) there will be
no automatic SAT at all. The operator can however start a SAT by
manually entering the PQ command.
With this item the operator can configure the height over which the
displacer is raised during the SAT.
With this item the operator can configure the time between two
consecutive SATs.
When set to 'N' (NO), during SAT
- An asterisk ('*') will be shown on the same position where
normally the arrow up/down symbols are displayed.
When set to 'Y' (YES), during SAT
- An asterisk ('*') will be shown on the same position where
normally the arrow up/down symbols are displayed.
- Both the measurement unit and the measurement type will be
set to exclamation marks.
- All level related GPU records will be invalidated.
- Items like QS, LQ, UQ and CQ are unaffected.
Operation