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5.4 Root extractor: root
This function is primarily intended for use with
differential flowmeters which have a square law
4/20mA output. The root extractor linearises the
flow signal enabling the BA554D to display rate
and total flow in linear engineering units.
To activate the square root extractor select 'root'
from the menu and press
P
which will reveal if
the function is 'On' or 'OFF'. If the function is
set as required, press
E
to return to the menu,
or press the
Up
or
Down
button to change the
setting, followed by the
E
button to return to the
main menu.
For reference, the following table shows the
output current from a non-linearised differential
flowmeter.
% of full flow Current output mA
2.5
4.01
10.0
4.16
25.0
5.00
50.0
8.00
75.0
13.00
100.0
20.00
5.5 Resolution: rESn
This function defines the resolution of the least
significant rate display digit. Decreasing the
display resolution can improve the readability of
a noisy signal. Select 'rESn' from the menu and
press
P
which will reveal the current display
resolution. To change the resolution press the
Up
or
Down
button to select 1, 2, 5 or 10 digits,
followed by the
E
button to return to the menu.
5.6 Position of the decimal points: d.P.
This function positions the decimal point in both
the rate and total displays.
The rate display can have up to five digits and
the decimal point may be positioned between
any of them, or omitted. The BA554D uses
floating point arithmetic
so moving the position
of the rate display decimal point will affect
totalisation. Similarly the total display has eight
digits and the decimal point may be positioned
between any of them, or may be omitted.
To adjust the position of either decimal points
select 'd.P.' from the main menu and press
P
which will activate both displays with one digit
and the following decimal point of the total
display flashing. If only the least significant digit
is flashing, this indicates that the decimal point
is omitted.
The position of the decimal point can be moved
by pressing the
Up
or
Down
push-button.
Operating the
P
push-button will toggle control
between the two displays. When both decimal
points have been correctly positioned press
E
to
return to the main menu.
If the application requires flow rate to be the
primary display i.e. shown on the large display,
the d.P. function enables the rate and total
displays to be interchanged. The rate display
will continue to have five digits but the total
display will be reduced from eight to six digits.
The rate and total annunciators will also be
interchanged. Pressing the
Up
and
Down
buttons simultaneously will interchange the
displays.
5.7 Calibration of rate display using an
external current source: CAL
This function enables the zero and span of the
rate display to be adjusted using an external
calibrated current source. When used with an
accurate traceable current source this is the
preferred method of calibration.
To calibrate the instrument select 'CAL' from the
main menu and press
P.
The indicator will
display 'ZErO' which is a request for a 4mA
input current. Adjust the external current
calibrator to 4.000mA and again press
P
which
will reveal the current instrument zero display.
For flow applications this will usually be zero.
Each digit of the rate display can be changed by
pressing the
Up
or
Down
buttons. When the first
digit is correct pressing
P
will transfer control to
the next digit. The most significant digit, which
can be 1 or 2 is set by rolling over the previous
digit. When all the digits have been adjusted,
press
E
to enter the new zero. The indicator will
display 'Ent' for a few seconds while the
information is being stored in memory, and will
then return to the 'ZErO' prompt .
To adjust the rate display at 20mA, press the
Up
button which will cause the instrument to display
'SPAn'. Adjust the external current calibrator to
20.000mA and again press
P
which will reveal
the existing full scale display. Each digit of the
rate display can be changed by pressing the
Up
or
Down
buttons. When the first digit is correct
pressing
P
will transfer control to the next digit.
The most significant digit, which can be 1 or 2 is
set by rolling over the previous digit. When all
the digits have been adjusted press
E t
o enter
the new span. The instrument will display 'Ent'
for a few seconds while the information is being
stored in memory and will then return to the
'SPAn' prompt. Finally press
E
again to return
to the main menu.
This function may also be used when calibrating
a complete loop from flow to instrument display.
