User Guide

5 Linearisation
Flowmeters are usually supplied with a calibration
certicate specifying their average K-factor and the ow
rangeoverwhichitapplies.Foruseoverextendedow
ranges and for non-linear owmeters, multiple K-factors
willbespeciedeachatadifferentowrate.Forthese
devicesthecalibrationcerticateislikelytocontainatable
similar to the one shown below.
Flow Rate
Litres/min
K-factor
Pulses/litre
5 200
10 230
15 239
20 242
Table3Typicalowmetercalibrationcerticate
To minimise display errors resulting from owmeter
non-linearity, all BEKA Rate Totalisers incorporate a 16
segment straight line lineariser which when correctly
conguredwillcompensatefortheowmeternon-linearity.
When the Rate Totaliser’s lineariser is enabled up to
16 valuesof the owmeter’sK-factor may beentered in
the l-factor function, each at a specied input pulse
frequency pul5e fre.
Theoutputfrequencyoftheowmeter,whichisrequiredfor
calibrating the Rate Totaliser lineariser, can be calculated
fromtheinformationintheowmetercalibrationcerticate.
OutputfrequencyHz=(Flowratepermin)x(K-factor)
60
Oriftheowrateisspeciedpersecond.
OutputfrequencyHz=(Flowratepersecond)x(K-factor)
Flow Rate
Litres/min
K-factor
Pulses/litre
Output
frequency
Hz
0 0 0
5 200 16.666
10 230 38.333
15 239 59.750
20 242 80.666
Table 4 Calculated lineariser calibration information
6 Pulse output
AlleldmountingBEKARateTotalisersandthe144x72mm
panel mounting models have an optically isolated open
collector pulse output. This pulse output is available as
afactoryttedoptionforthesmaller96x48mmandthe
rugged 105 x 60mm panel mounting models.
The output pulse may be a synchronous duplicate of the input
pulse for re-transmission applications, or it may be derived
fromincrementationoftheleastsignicantdigitofthetotal
display, irrespective of the decimal point position. When
derived from the total display the output pulse frequency
maybedividedandtheoutputpulsewidthdened.
Selecting dirECt inthe pulseoutput congurationmenu
produces a synchronous duplicate of the Rate Totaliser
inputpulseatfrequenciesupto5kHz.
When 5CALEdisselectedinthepulseoutputconguration
menu, the pulse output is derived from the incrementation
oftheleastsignicantdigitofthetotaldisplay,irrespective
of the position of the displayed decimal point. When
5CALEd is selected the Rate Totalisers pulse output
frequency may be divided by:
1
10
100
1000
10000
and the pulse output width (duration) may be selected
from eleven options:
0 . 1 ms
0 . 5 ms
1 ms
2 . 5 ms
5 ms
10 ms
25 ms
50 ms
100 ms
250 ms
500 ms
If congured such that the output pulse frequency with
the speciedpulse width cannot be outputin real time,
the number of pulses will be stored and transmitted at
the maximum possible speed, but will not be stored if
the total displayisreset to zero or the RateTotaliseris
disconnected or switched off.
To prevent misleading or dangerous pulse outputs after
anychangesaremadetotheRateTotaliserconguration,
the pulse output must be manually re-enabled before it will
function.
The pulse output of a two input Rate Totaliser may be a
synchronous duplicate of either pulse input, or it may be
derivedfromincrementationoftheleastsignicantdigitof
thecompositetotaldisplay(inputA+inputb)irrespective
of which total is being displayed by the instrument.
A pulse output can not be derived from a composite total
displayof(inputA-inputb).
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