User guide

Rev. 10/08 - 29 - D902/3
PART 4 - TROUBLESHOOTING
FAULT light is ON; low SIGNAL
STRENGTH indication (continued)
If GND connection and pipe are at different
potentials, ground D902/3 to pipe potential.
If Variable Frequency Drives are being
utilized, verify that the D902/3 obtains a
READ light when the pump is turned OFF.
If possible, increase the carrier frequency
of the drive.
Stability of flow readings are
unsatisfactory
Increase the DAMP constant from keypad.
Increase the system time constant by
turning R17 (DAMP) clockwise till readings
are satisfactory.
Move transducers to a location further from
piping tees, elbows, valves, filters, etc.
Erroneous Reading
Transducers mounted incorrectly.
Another local ultrasonic instrument is
operating at about the same frequency
(consult the Dynasonics factory).
Presence of large amounts of suspended
solids or aeration. Use CAL constant to
compensate.
Sources of radiated interference are
present. Apply appropriate shielding.
An electrically noisy power supply is
powering the D902/3. Power the meter
with a circuit that does not power motors,
ballasts or switching supplies.
The D902/3 display indicates flow, when
true fluid velocity is zero
Verify that residual leakage and flow are
not present (i.e. leaking check valves).
Verify that SENSITIVITY is not adjusted
too high. With nominal flow running
through the pipe, adjust SENSITIVITY
control till the right-most bar meter light just
comes ON.
This procedure requires the
face plate to be removed
from the enclosure.