FDT-25W Wall Mounter Ultrasonic Flowmeter
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2.8.2 Signal quality
Signal quality is indicated as the Q value in the instrument. A higher Q value would mean a higher
Signal and Noise Ratio (short for SNR), and accordingly a higher degree of accuracy would be
achieved. Under normal pipe condition, the Q value is in the range 60.0-90.0, the higher the better.
Causes for a lower Q value could be:
(1) Interference of other instruments and devices such as a powerful transverter working nearby. Try to
relocate the flow meter to a new place where the interference can be reduced.
(2) Bad sonic coupling for the transducers with the pipe. Try to apply more couplant or clean the
surface, etc.
(3) Pipes are difficult to be measured. Relocation is recommended.
2.8.3 Time Ratio between the Measured Total Transit Time and the
Calculated Time
This ratio would be used to check the transducer installation. If the pipe parameters are entered
correctly and the transducers are installed properly, the value for this ratio should be in the range of
100±3. If this range is exceeded, the user should check:
(1) If the pipe parameters are correctly entered.
(2) If the actual spacing of the transducers is right and the same as what the window M25 shows.
(3) If the transducers are installed properly in the right directions.
(4) If the mounting location is good and if the pipe has changed shape or if there is too much fouling
inside the pipes
(5) Other poor condition
3. Menu Window Details
3.1 Menu Windows Arrangement
M00~M09 windows for the display of the flow rate, velocity, date time, totalizers, battery voltage and
estimated working hours for the battery.
M10~M29 windows for entering the pipe parameter.
M30~M38 windows for flow rate unit selections and totalizer unit selections.
M40~M49 windows for response time, zeroing, calibration and modification password setup.
M50~M53 windows for the built-in logger
M60-M78 windows for time-keeper initialization, version and ESN information viewing and alarms.