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6.0 SAFETY, MAINTENANCE, AND TROUBLESHOOTING
6.4.2 Sensor Inspection
The sensor of the AT100 consists of a metal tube containing several wires. The sensor tube will measure
the float location properly if the tube is straight and the float can travel freely up and down its length. Perform a
visual inspection on the sensor tube to make sure it is straight, free from pits or gouges, and does not show
excessive wear patterns.
6.4.3 Transmitter Testing
The transmitter of the AT00 is designed to return a level indication and an output based on the position of a
float on its sensor tube. If the transmitter is equipped with an LCD the level and output will be displayed on the front
of the electronics module.
1) Apply power to the AT100 using the typical power setup for the particular option.
2) Move the float up and down the sensor tube.
3) Monitor the indication of the level on the LCD to make sure the indication corresponds to the float position.
4) Remove the float to make sure the transmitter responds with an Alarm Indication (based on the jumper position) and
a level indication of ****.
5) Replace the float.
Note: It is possible for the AT100 to continue providing a 4-20mA output if the LCD display is not functioning
properly. If the LCD indicator on an electronics module fails to operate, it is recommended that the electronics
module be replaced at the earliest convenience. It will not be necessary however to shut down a transmitter or
remove it from service based on an LCD failure.
6.4.4 Output Checkout
The AT100 can be equipped to provide level indication through the 4-20mA output, HART communications,
Foundation Fieldbus, or Honeywell DE depending on the model ordered. Only transmitters that are specified to
output 4-20mA may be used in a Safety Implemented System. The HART communication capability of the 4-20mA
transmitter will only be used for configuration and proof testing.
6.4.4.1 4-20mA Output
The current output of the AT100 transmitter update at least every 110 milliseconds and be filtered through
the user adjusted Damping. The maximum response time to a process change will be less than 110 milliseconds or
the value of the Damping, whichever is greater.
1. Apply power to the transmitter using the typical loop wiring diagram in Section 8.0.
2. Connect a multi-meter (set to read milliamps) to the transmitter using the "Meter" connections on the
terminal strip.
3. Move the float along the length of the probe and monitor the milliamp output on multi-meter .
4. The output should indicate the float position based on the calibration range of the transmitter.
6.4.4.2 HART Output
1. Apply power to the transmitter using the typical loop wiring diagram in Section 8.0.
2. Connect a HART handheld device across a 250 ohm resistor in series with the loop.
3. Move the float along the length of the probe and monitor the PV indication on the handheld device.
4. The output should indicate the float position based on the calibration range of the transmitter.
Note: A HART handheld device will communicate with the AT transmitter as a Generic Device. If the output
of the transmitter becomes latched, the HART handheld will respond with a warning that the Process Variable is out
of range. To overcome the error, press OK when prompted to "ignore the next 50 occurrences."
AT100-0200-1 Rev L (10-2010) DCN0528
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