K-factors explained
Page 13
SGN-UM-00282-EN-05
June 2021
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 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 1 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 1 gpm The output frequency, in Hz, is found
simply by dividing the number of counts (1000) by the number of seconds (60)
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 1 gpm If the
frequency counter registered 33 333 Hz (2 × 16 666 Hz), then the flow rate would
be 2 gpm
Finally, if the flow rate is 2 gpm, then the accumulation of 1000 counts would take
place in 30 seconds because the flow rate, and hence the speed at which 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 An accurate flow rate and the output frequency
associated with that flow rate is required for the most basic K-factor calculation
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
=
=
