dynasonics TFX Ultra User Manual

KFACTORS
Description
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 transmitters are capable of measuring flow in a wide range of pipe sizes. Because the pipe size and volumetric
units the transmitter 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 transmitter 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.
Example 3
Known values are:
Velocity = 4.3 ft/sec
Inside Diameter of Pipe = 3.068 in.
KFactors
Page 106 May 2016TTM-UM-00136-EN-06

dynasonics TFX Ultra Specifications

General

Brand	dynasonics
Model	TFX Ultra
Category	Measuring Instruments
Language	English