Badger Meter B3000 - Manual (Page 38)

Compact Digital Flow Monitor, Model B3000
Page 38 March 2014
K FACTORS EXPLAINED
The K factor (with regards to flow) is the number of pulses that must be accumulated to equal a particular volume of fluid You
can think of each pulse as representing a small fraction of the totalizing unit
An example might be a K factor of 1000 (pulses per gallon) This means that if you were counting pulses, when the count total
reached 1000, you would have accumulated one gallon of liquid Using the same reasoning, each individual pulse represents
an accumulation of 1/1000 of a gallon This relationship is independent of the time it takes to accumulate the counts
The frequency aspect of K factors is a little more confusing because it also involves the flow rate The same K factor number,
with a time frame added, can be converted into a flow rate If you accumulated 1000 counts (one gallon) in one minute, then
your flow rate would be one gpm The output frequency, in Hz, is found simply by dividing the number of counts (1000) by
the number of seconds in a minute (60) to get the output frequency
1000 ÷ 60 = 16 6666 Hz If you were looking at the pulse output on a frequency counter, an output frequency of 16 666
Hz would be equal to one gpm If the frequency counter registered 33 333 Hz (2 × 16 666 Hz), then the flow rate would be
two gpm
Finally, if the flow rate is two gpm, then the accumulation of 1000 counts would take place in 30 seconds because the flow
rate, and hence the speed that the 1000 counts is accumulated, is twice as great
Calculating K factors
Many styles of flow meters are capable of measuring flow in a wide range of pipe sizes Because the pipe size and volumetric
units the meter will be used on vary, it may not possible to provide a discrete K factor In the event that a discrete K factor is
not supplied then the velocity range of the meter is usually provided along with a maximum frequency output
The most basic K factor calculation requires that an accurate flow rate and the output frequency associated with that flow
rate be known
Example 1
Known values are:
Frequency = 700 Hz
Flow Rate = 48 gpm
700 Hz × 60 sec = 42,000 pulses per min
42,000 pulses per min
K factor
48 gpm
875 pulses per gallon = =
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
K factor
39,000 pulses per min
85 gpm
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 one US gallon of liquid is equal to 231 cubic inches