BEKA BA384E, Руководство пользователя

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7. LINEARISERS
The BA384G Rate Totaliser can produce accurate
results when used with flowmeters having K-factors
that vary with the flow rate, such as a turbine meter
used over a wide range of flows. Each channel of
the Rate Totaliser has an independent sixteen
segment straight-line lineariser that may be adjusted
to compensate for the nonlinearity of the flowmeter
connected to the input as shown in Fig 11.
The two linearisers are enabled by selecting
Lin
in
FunCtion
– see section 6.4. 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 in the
factor a
and
factor-b
functions.
Fig 12 shows how the
Factor-a
is extended.
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 linearisers
without having to reconfigure them.
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/minute
K-factor
Pulse/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 16.66
10 230 38.33
15 239 59.75
20 242 80.66
7.2 Summary of lineariser configuration
functions
This section summarises the lineariser configuration
functions. When read in conjunction with Fig 11 it
provides a quick aid for configuring each of the two
linearisers. 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.