GE AT868 AquaTrans Ultrasonic Flow Meter Field Maintenance and Troubleshooting Guide

Operation steps (be sure to disconnect the power first):

Loosen the 6 hexagon socket screws on the front cover and remove the front cover.

Remove the 4 mounting screws (including flat pads and spring pads) on the LCD/keypad.

Gently lift up the LCD panel and unplug the button ribbon cable from the connector below.

Insert the ribbon cable of the new board into the connector and lock it tightly. Align the pins again and press them firmly.

Reinstall the screws and washers, cover the front cover and power on for testing.

3.2 Replacing fuses

Applicable scenario: The device is completely without power.

Fuse specifications:

85-265 VAC power supply: 0.25 A, slow melting (Slo Blo), 3AG size

12-28 VDC power supply: 2.0 A, slow melting

Operation steps:

Remove the front cover after power failure.

Remove the 4 screws from the bottom mounting plate and take out the mounting plate.

Find the fuse holder (with plastic cover), pry open and remove the old fuse.

Install a new fuse according to the voltage level and replace the plastic cover.

Reassemble and record the replacement date (recommended Appendix E Service Record).

3.3 Replacing User Program EPROM

Applicable scenario: The device needs to upgrade firmware or restore factory programs.

Attention: EPROM is sensitive to static electricity, be sure to touch the grounded metal before operation to discharge.

Operation steps:

Remove the LCD board and Channel 1 board (see manual section 7-4 for details).

Find the U4 EPROM socket (the only socket chip with a white label).

Carefully pry out the old EPROM with a chip screwdriver or paper clip.

Align the angled edges of the new EPROM with the angled edges of the socket, and press evenly until fully seated.

Reverse assemble all components and check if the version number is correct after powering on.

Chapter 4: Calibration and Linear Testing of Analog Output and Frequency Output

The 4-20 mA output and frequency/accumulator output of AT868 need to be calibrated regularly to ensure measurement accuracy.

4.1 Analog output calibration

Preparation: Connect an ammeter with an accuracy of not less than 0.01 mA in series in the output circuit.

Low end calibration (4 mA):

Enter CALIB → SLOTO → A or C.

Select "4 mA" and use the UP/DOWN keys to adjust the output until the ammeter displays 4.000 mA.

Select STORE to save.

High end calibration (20 mA):

Select '20 mA', adjust to 20.000 mA and save.

If it is not possible to calibrate within ± 5 μ A, choose ABORT and contact the manufacturer.

4.2 Linearity Test

After calibration is complete, set the output to 50% full range (12 mA) and check if the ammeter reading is within the range of 12.000 ± 0.005 mA. Test the 0%, 25%, 75%, and 100% points in sequence and record the deviation.

4.3 Frequency output test

Enter CALIB → SLOTO → B or D, input the target frequency (such as 1000 Hz), and measure the output terminal with a frequency meter. If the deviation is too large, check whether the external load exceeds the specified value.

Chapter 5: System Diagnosis and Signal Tracking Techniques

AT868 provides rich diagnostic parameters that can be monitored in real-time by setting them as LCD display items.

Recommended diagnostic parameter configuration

In GLOBL → I/O → LCD, set # of LCD PARAMS=4 and select:

SS up: Upstream signal strength (normal 50-75)

SS dn: Downstream signal strength (normal 50-75)

SNDSP: Measurement of Fluid Sound Velocity

AMPup: Upstream signal amplitude (normal 24 ± 5)

Real time tracking window

When the fluid velocity changes frequently (such as large changes in water temperature), it is recommended to enable the tracking window:

CHx → PIPE → TRACKING WINDOW=YES.

The device will dynamically adjust the sound speed parameters to avoid E2 errors. If the sound speed is stable, the tracking can be turned off after reading the measured value, and the sound speed can be manually input to accelerate the response speed.

Signal quality (Q value) evaluation

Qup/Qdn should be ≥ 1200 normally

If it is between 400-1200, there may be noise interference in the signal

If it is below 400, the cable shielding, grounding, and sensor coupling should be checked.

Chapter 6: Special Investigation of Sensor (Transducer) Problems

6.1 Common problems with wet sensors

Leakage: Check the process connection. If the fluid is corrosive, both the sensor surface and the cable need to be checked simultaneously.

Corrosion: If there are pitting or roughness on the sensor surface, the sensors should be replaced in pairs and the new sensor number should be entered in CHx → PIPE.

Physical damage: Falling or impact often causes connector deformation, which can be corrected carefully; If the internal crystal breaks, it must be replaced.

6.2 Common problems with clamp type sensors

Poor coupling: Remove paint and rust from the pipe wall, reapply coupling agent (grease or epoxy resin), and ensure sufficient clamping pressure.

Misalignment: Install strictly according to the calculated sensor spacing (S value) and ensure that the two sensors are on the same axis plane.

Cycle Skip: manifested as E6 error, often caused by coupling agent failure or pipe wall scaling. Re couple and check if the inner lining of the pipe wall has come off.