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5. PROGRAMMING & CALIBRATION
The BA554D is programmed and calibrated via
four push-buttons which are located behind the
instrument control cover. If frequent access to
the push-buttons is required, the rate totaliser
can be supplied with duplicate membrane push-
buttons mounted on the outside of the control
cover.
All the programming functions are contained in
an easy to use menu which is shown
diagramatically in Figs 7A and 7B. Each
function is summarised in section 5.3 which
includes references to more detailed
information. Although this simple menu driven
system enables most adjustments to be made
without repeated reference to this manual, it is
recommended that at least the summary of the
programmable functions in section 5.3 is read
before attempting programming or recalibration.
When the instrument is fitted with alarms, the
basic menu is expanded to include the alarm
functions which are described in section 8.2 of
this manual.
Note:
While the instrument is being
programmed or calibrated totalisation is
suspended, any flow occurring during this time
will not be recorded,
5.1 Calibration structure
Fig 6 shows the BA554D calibration structure.
The 4/20mA input current, which in flow
applications represents flow rate, is displayed on
the five digit display. Using the instrument’s
'CAL' or 'SEt' functions this display may be
calibrated to show the flow rate in engineering
units. Both the zero (display at 4mA) and the
span (display at 20mA) are adjustable, although
for flow application the display at 4mA is usually
zero.
The position of the decimal point in the rate
display is defined by the d.p. function. To
simplify calibration the BA554D uses
floating
point arithmetic.
Moving the position of the
decimal point in the rate display will therefore
affect totalisation.
Fig 6 Calibration structure
The BA554D total display is calculated from the
rate display using two serial factors: the
timebase 't-bASE' and the total scaling factor
'SCALE-t'. The timebase divides the rate
display according to whether the rate display
represents flow per second, per minute or per
hour. The total scaling factor 'SCALE-t' is a
wide range programmable dividing factor
allowing the rate and total displays to be in
different units.
For example, if a BA554D is displaying rate in
litres per minute, setting 'SCALE-t' to 4.5461
produces a total display in UK gallons.
Alternatively, setting 'SCALE-t' to 4546.1 will
produce a total display in thousands of UK
gallons.
The total is calculated and the display updated
once every second, which defines the resolution
of the total flow display. When total alarms are
used for batching applications, this resolution
may define the system accuracy.
