Downlook Ultrasonic Sensor Troubleshooting - Hach 900 MAX Instrument Manual

Appendix C

Downlook Ultrasonic Sensor Troubleshooting

Problems
RS485 Time Out—Did not get a
reading with the specified time
allotted.
Loss of Ultrasonic as Level
Measuring Device.
U-Sonic Echo Loss—Flow Meter
Not Receiving a Return Echo
from the Ultrasonic Transducer.
U-Sonic Failure—No Signal from
the Ultrasonic Transducer.
XDucer Ringing—False Return
Echo mask Real Echoes.
No Change in Level Readings or
Inaccurate Level Readings.
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Troubleshooting and Error Messages
Causes
CPU is having trouble communicating
with the Ultrasonic board.
Difficulty receiving a velocity reading.
Blown fuse on CPU board.
Problem with the ultrasonic board.
Excessive foam on the water surface
causes sound waves to be absorbed
rather than reflected.
Sensor is knicked or cut or improperly
installed.
Sensor must be level for proper return
of signals.
Convection currents are present which
varies the speed of sound.
Temperature calibration set up incorrectly.
Extreme high or low temperature
indicates a bad temperature transducer in
the temperature sensor.
Transducer is not connected.
Cut or broken cable.
Unusual temperature or inability to read
new calibrated level.
Liquid is too close to the transducer.
Obstructions under the transducer.
Coating on the face of the transducer.
The transducer resonates against steel
mounting rails.
—
Calibration
Bad transducer.
Solutions
Wait a few minutes and see if the condition
goes away. If it continues there amy be a
problem in the Ultrasonic, Velocity, or
CPU board.
Indicates an internal problem.
Replace fuse. The fuse is located in position
F1 under the gray ribbon cable that connects
at position J1.
Replace if necessary.
Check for excessive foam.
Check for knicks, cuts, and the
sensor installation.
Make sure the ultrasonic transducer is level.
Try shielding the transducer from convection
currents. Echo loss should not exceed more
than two hours.
Go through the temperature calibration
procedure and determine what the
temperature the unit is sensing. Replace
transducer if necessary.
Check the ultrasonic sensor connection on the
flow meter.
Check for any knick or cuts in the cable.
Re-calibrate the unit.
Try moving the transducer farther from the
liquid.
Check for obstructions on the front and sides
of the transducer.
Clean the transducer face. If this is a constant
problem, try coating the face of the transducer
with a very thin film of silicone grease to keep
the debris from collecting.
Use the proper rubber isolation washers.
Check the logged data to see when this
started to occur. Go to the event log to see if
anything happened during the same time.
Re-calibrate the unit.
Try a different transducer.
8990apdx_tbl.fm