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6.0 SAFETY, MAINTENANCE, AND TROUBLESHOOTING
6.9 Threshold Adjustment
If the output occasionally jumps to an alarm condition (**** on display), this can be an indication of a loss of
signal or a transmitter threshold voltage not set properly. The adjustment can be done as follows
Note:
It is preferable to make this adjustment with the float located towards the end of the sensing tube, away from
the transmitter housing, but within the normal measuring range.
done on the unit.
Locate adjustment potentiometer next to the bottom right of the electronics module.
With unit powered up, turn adjustment CLOCKWISE until the output goes and stays in alarm (3.6mA or 21 mA).
Turn adjustment slowly COUNTER-CLOCKWISE until a steady output is established. This output should match
the float position.
Turn adjustment slowly COUNTER-CLOCKWISE and keep track of the number of turns, until the output is not
stable any more.
Turn adjustment back CLOCKWISE, half the amount of turns recorded in previous steps. Verify that a steady
output is achieved.
Proper orientation of
the electronics module.
Mounting Screws
6.10 Module Replacement
The AT100 transmitter is equipped with modular electronics which may be removed from the housing. An
EPROM and a threshold adjustment potentiometer located in the transmitter housing will maintain the settings of the
transmitter if the electronics are removed. This allows the replacement of failed electronic modules and upgrading of
electronics or transmitter software without loosing calibration and setup configuration.
Before removing the electronics module for replacement or upgrade, the AT100 transmitter should be taken
out of service. To remove the electronics module, simply loosen the 2 mounting screws, unplugging the module
from the housing and replace it with the new module.
The software revision of a transmitter can be identified by a tag on the back of the electronics module. The
date code of the software revision will appear as a series of numbers such as AT_H_090209 or AT_H_TS_090209.
The type of module will be identified on the same tag with a code such as M4AS or M4BS.
WARNING:
In order to maintain certification requirements, repair of the instrument at the electronic component level can
only be performed at the factory. Field repair of electronics components should only involve replacing electronic modules.
Opening the electronics module will void all warranties of the transmitter.
6.11 Terminal Strip Checkout
Moisture within the housing may cause failure of the RFI filtering within the terminal strip. This can be
indicated as a current output that is higher than the current indicated by the LCD Display. To verify terminal strip
failure, remove the field wiring and the electronics module. Using a multi-meter, check the resistance from each of
the terminal points to the housing. All of the terminal positions should indicate open to the housing. Consult the
factory for terminal strip servicing procedures.
AT100-0200-1 Rev L (10-2010) DCN0528
This is the only adjustment that can be
CALIBRATE
sec
SETUP
TRIM
F C
%
mm
in
cm
mA ft
S
E
L
E
C
T
Threshold Voltage Potentiometer
Cutout Corner
26
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