Chapter 2 Starting Measurement
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2.9.2 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 600-900, the higher the better. Causes for a lower Q value could be:
(l) 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 coupler
or clean the surface, etc.
(3) Pipes are difficult to be measured. Relocation is recommended.
2.9.3 Total Transit Time and Delta Time
The numbers displayed on menu window M93 are called total transit time and delta
time respectively. They are the primitive data for the instrument to calculate the
flow rate inside the pipe. so the flow rate indication will vary accordingly with the
total time and delta time.
The total transit time should remain stable or vary little.
If the delta time fluctuates higher than 20%, it means there are certain kinds of
problems with the transducer installation.
2.9.4 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 1003. 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 conditions.
