Badger Meter Cox Precision Turbine Meters - Manual (Page 11)

TECHNICAL TERMS
Several terms, such as K-Factor and linearity, are used to indicate turbine flow meter performance .
K-Factor
“K” is a letter used to denote the cycles per gallon factor of a flow meter . This factor is a fixed value used in resolving or
totalizing the pulse count output of a flow meter . It results from the equation:
Cycles per second/Gallons per second = Cycles per gallon (K)
Repeatability
The maximum deviation from the corresponding data points taken from repeated tests under identical conditions .
Linearity
This is defined as the deviation from the mean calibration factor (K) and is expressed as being within a certain tolerance . Cox
Precision Turbine Flow Meters are linear to ± 0 .5% over the range shown .
CALIBRATION DATA
K-Factor
The calibration data supplied with a Cox Precision Turbine Flow Meter is shown in Figure 6 .
Correct application of a Cox Precision Turbine Flow Meter requires consideration of many important factors . Because of
the wide variation of possible applications, detailed data for liquid flow models only is given in this manual . For special
requirements—such as those outside the range of –300…350° F, those with extremely corrosive liquids, gases and other
unusual conditions—consult the Badger Meter Sales Department .
20-Point Calibration
Calibration at twenty flow rates (10 up-scale and 10 down) between minimum and maximum flow range, is available for
application where ± 0 .25% accuracy or better is required . With this calibration complete data on signal output, pressure drop,
K-Factor and deviation from linearity is supplied .
30-Point Calibration
This is the same as the 20-point, with 10 extra points to cover the longer range of the carrier type meters .
UVC-Universal Viscosity Curve
A 10-point calibration is made at each of four viscosities if curves of “K” versus Hertz were made . In between, viscosities cannot
be determined (see right side of Figure 5 ) . Replot as “K” versus Hertz divided by centistokes . A single curve is drawn through all
data points . Other viscosity curves can now be determined . Use only over 10:1 range for viscosity effects .
Gas Calibrations
When performed at the Flow Dynamics facility, a curve of ACFM vs . Hertz is supplied .
Pressure Rating
The standard LoFlo and Precision Flow Meters are rated 2500…5000 psi operating pressure . They have a 4:1 pressure safety
factor . Flange flow meters are rated for service pressure according to ANSI ratings for the flanges used .
Operation at temperatures above 200° F will decrease the connection rating because of lowered stress capabilities of
the metal .
Liquid Formula Gas Formula
= ( Ч 60) ч
= Ч 3600 Ч 8.328 Ч . .
=
. −
Figure 5: Calculating flow rates in different units
User Manual
Page 11 May 2014