Dynasonics 902_903 Series Portable Doppler Ultrasonic Flow Meter - Manual (Page 31)

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.