Badger Meter ER-500 - Page 26

Example 2:
Known values are:
Full Scale Flow Rate = 85 gpm
Full Scale Output Frequency = 650 Hz
650 Hz × 60 sec = 39,000 pulses per min
39,000 pulses per min
85 gpm
K-factor 458.82 pulses per gallon= =
The calculation is a little more complex if velocity is used because you first must convert the velocity into a volumetric flow
rate to be able to compute a K-factor.
To convert a velocity into a volumetric flow, the velocity measurement and an accurate measurement of the inside diameter
of the pipe must be known. Also needed is the fact that 1 US gallon of liquid is equal to 231 cubic inches.
Example 3:
Known values are:
Velocity = 4.3 ft/sec
Inside Diameter of Pipe = 3.068 in.
Find the area of the pipe cross section.
2
 
 
 
3.068
2
A
rea =
πr
2
A
rea = π = π x
2.35 = 7.39 in
2
Find the volume in 1 ft of travel.
88.71in
2
7
.3 in
2
x 12 in (1 ft) =
ft
What portion of a gallon does 1 ft of travel represent?
= 0.384 gallons
88.71 in
3
231 in
3
So for every foot of fluid travel 0.384 gallons will pass.
What is the flow rate in gpm at 4.3 ft/sec?
0.384 gallons × 4.3 FPS × 60 sec (1 min) = 99.1 gpm
Now that the volumetric flow rate is known, all that is needed is an output frequency to determine the K-factor.
Known values are:
Frequency = 700 Hz (By measurement)
Flow Rate = 99.1 gpm (By calculation)
700 Hz × 60 sec = 42,000 pulses per gallon
K-
factor
42,000 pulses per min
99.1 gpm
423.9 pulses per gallo
n
==
Modbus Interface
DSY-PM-00028-EN-02Page 26 February 2017