BEKA BA337E, Manual

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7. LINEARISER
The BA337E and BA338E Rate Totalisers 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.
Both models include 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 12 shows how the Rate Totaliser configuration
function
FACtor
is extended when the lineariser is
activated by selecting
Lin
in the
FunCtion
menu.
Fig 11 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 12 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.
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