Instruction Manual

Rev. 04/02 -30- D901/M
PART 4 - TROUBLE SHOOTING
FAULT light is ON; low SIGNAL
STRENGTH indication (continued)
• If GND connection and pipe are at
different potentials, ground D901/M to
pipe potential.
• If Variable Frequency Drives are being
utilized, verify that the D901/M obtains a
READ light when the pump turn OFF. If it
does, contact the Dynasonics factory.
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 D901/M. Power the meter
with a circuit that does not power motors,
ballasts or switching supplies.
Readings of flow at zero fluid velocity
• Verify that residual leakage and flow is 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.