4.2 Configuration Parameters
4.2.1 Basic Configuration Parameters
shows the primary configuration parameters.
Figure 4-2. Parameters Tab
The F1, Gap, and Gain parameters are the only parameters which should be initially adjusted. All other
parameters should be set to their default values for 1-MHz transducers. These parameters control the excitation,
amplification, and ADC capture time between the ultrasonic transducers connected to the platform.
Set the "Transmit Frequency" to the nominal frequency of the transducers in kHz (for example, set to 1000 for 1-
MHz transducers). Tune this parameter after the frequency sweep (described in
) is conducted. After
the other parameters have been properly determined, tune the transmit frequency to give a better signal
response as described in
.
Set the "Gap between pulse start and ADC capture" based on the anticipated ultrasonic time of flight for a given
flow tube with enough additional capture time to address signal shifts due to temperature variations.
The "GUI Based Gain Control" controls the gain of the integrated PGA. Set this parameter to give an ADC
capture of no more than ±900 ADC counts in the ADC capture tab. Although the system should be operable with
signals down to ±150 ADC counts, setting the gain to give higher ADC counts reduces the standard deviation in
measurements.
For example, a DN-25 pipe might have an ultrasonic path which corresponds to a time of flight of approximately
65 µs. This is based on an ultrasonic path between transducers of approximately 9.5 cm and the speed of sound
in water (1450 m/s). An appropriate "Gap" that would ensure there is enough time before the signal to
accommodate shifts due to temperature variations might therefore be 60 µs. The ultrasonic distance between
USS GUI
6
Water Flow Meter
SLAU810B – SEPTEMBER 2019 – REVISED SEPTEMBER 2020
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