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6.4 Root extractor: root
This function is primarily intended for use
with differential flowmeters that have a
square law 4/20mA output. The root
extractor linearises the flow signal and
enables the BA358C to display flow and total
in linear 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
6.5 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.
6.6 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
BA358C 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 pointof
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 points can be
moved by pressing the Up or Down push-
buttons. 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.
6.7 Calibration of the 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 current source such as a 4/20mA
calibrator. 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. 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 to enter the new span. The
instrument will display 'Ent' for a few
seconds while the information is being
