K-Factors Explained
Page 41
May 2020
DSY-PM-01378-EN-08
K-FACTORS EXPLAINED
The K-factor (with regard 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 is 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 (1 gallon) in one minute, then your flow rate would be 1
gpm� The output frequency, in Hz, is found 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 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 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 varies, it may not
be 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
=
=
