Dynasonics D7700 Series Insertion Doppler Ultrasonic Flow Meter - Manual (Page 27)

Rev. 2/00
-4.4- 77X
C.W. Time the new rate and adjust as required. For
example, if the flow indicator reads 1,000 GPM and a
totalizer count rate of 1 count every 60 seconds
should be displayed. If the actual count rate is one
count every 50 seconds, then turn the adjustment
R90 slightly (with SW 1 Position x 1,000) C.C.W. to
decrease the count rate until there is one count on
the totalizer every 60 seconds when the flow rate
indicator is reading 1,000 GPM. As noted above, 20
full turns on R90 will produce a variation in count rate
of at least x 10, or from approximately 50 to 500
seconds when the indicator is reading full scale. To
determine count rate:
60 (TM)
Count rate = -----------------
GPM
Where,
TM = totalizer multiplier or gallons x totalizer counts
GPM = flow at time of calibration
Electronic Calibration
The flowmeter is electronically calibrated at the
factory by calculating the fluid velocity in Feet per
Second (FPS) that corresponds to the pipe size and
volumetric flow rate that was customer supplied at the
time of the order. The following equations were used
to determine the “calibration frequency” that is
required to properly span the flow meter.
FPS = GPM
(PIPE I.D.)
2
X 2.45
Where
PIPE I.D. is inches
A DP7 transducer generates 120 Hz / 1 FPS of
frequency shift when operated on room temperature
water. Alternate fluids can influence this factor. See
PART 4 - CONFIGURATION AND OPERATION