BEKA BA334NG, Manual

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7. LINEARISER
The BA334NG Rate Totaliser can produce accurate
results when used with a flowmeter having a
K-factor that varies with the flow rate, such as a
turbine meter used over a wide range of flows. The
instrument includes a sixteen segment straight-line
lineariser that may be adjusted to compensate for
flowmeter non-linearity.
The lineariser is enabled by selecting
Lin
in the
FunCtion
section of the configuration menu. The
configuration menu shown in Fig 10 remains
basically unchanged, except that up to 16 values of
the flowmeter K-factor can be entered as
l-factor
,
together with
pul5e fr
the corresponding input
frequency at which each starts.
Fig 14 shows how the Rate Totaliser configuration
function
FACtor
is extended when the lineariser is
activated by selecting
Lin
in the
FunCtion
menu.
Fig 13 shows a typical linearising characteristic
The lineariser configuration is retained irrespective
of how
FunCtion
in the Rate Totaliser configuration
menu is subsequently changed. It is therefore
possible to select and deselect the lineariser without
having to reconfigure it.
7.1 Flowmeter specification
Flowmeters are usually supplied with a calibration
certificate specifying the average K-factor and the
flow range over which it applies. For use over
extended flow ranges and for non-linear devices,
multiple K-factors will be specified, often in a table
similar to the one shown below.
Flow Rate
Litres/min
K-factor
Pulses/litre
5 200
10 230
15 239
20 242
From this calibration certificate information the
output frequency of the flowmeter, which is
required for conditioning the Rate Totaliser
lineariser, can be calculated.
Output frequency Hz = (Flow rate per min) x (K-factor)
60
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
7.2 Summary of lineariser configuration
Functions.
This section summarises the lineariser
configuration functions. When read in conjunction
with Fig 14 it provides a quick aid for configuring
the lineariser. If more detail is required, each
section contains a reference to a full description of
the function.
The number of straight-line lineariser segments
required should first be entered using the
Add
and
del
functions. In both of these sub-functions the
Rate Totaliser displays the current segment and
the total number of segments being used as shown
below.
Increasing the number of segments will provide a
more accurate approximation of the flowmeter
characteristic and increase totalisation accuracy.