13
This function may also be used when
calibrating a complete loop from primary
element to indicator display e.g. when the
indicator is displaying the output from a level to
current converter.
6.9
Calibration using internal references:
SEt
This function enables the zero and span of the
digital indicator to be adjusted without the need
for an accurate external current source, or for
disconnection from the 4/20mA loop.
The accuracy of this method depends upon the
accuracy of the internal references which
should be regularly calibrated as described in
section 6.10.2
The analogue
bargraph is
automatically
calibrated when the digital display is calibrated,
no separate adjustments are required.
Fig 7
shows the analogue display resulting from
various digital display calibrations.
To calibrate the indicator select 'SEt' from the
main menu and press
P.
The indicator will
display 'ZErO', pressing
P
again will reveal the
current display at 4mA. Each digit, except the
dummy zero if activated, of the indicator
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 the least significant digit has been
adjusted, press
E
to return to the 'ZErO'
prompt which completes the adjustment.
To adjust the display at 20mA, press the
Up
button which will cause the indicator to display
'SPAn'. pressing
P
again will reveal the
indicator display.
Each digit of the display,
except the dummy zero when activated, 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
the least significant digit has been adjusted
press
E t
o return to the 'SPAn' prompt followed
by
E
to return to the menu.
6.10 Conditioning sub-menu: Cond
This is a password protected sub-menu which
allows the mains (line) frequency at which the
indicator has maximum ac rejection to be
selected, and the two internal references to be
calibrated.
To gain access to the sub-menu select 'Cond'
from the main menu and press
P
.
The
indicator will display '0000'. Using the
Up
and
Down
buttons and the
P
button to move to the
next digit enter the password 'SurE'. (Note that
'S' is entered as '5'). Pressing E will then give
access to the two functions in the sub-menu.
6.10.1 AC rejection: FrE
CAUTION
If the mains filter frequency is changed,
the
indicator
display
and
internal
references
(if
used)
must
be
recalibrated.
To provide maximum low frequency rejection
the internal digital filter may be set to operate
at 50 or 60Hz to correspond with the local
mains (line) frequency.
To change the
frequency select 'FrE' from the 'Cond' sub-
menu and press
P
which will reveal the current
setting. The setting can be toggled between
the two options by pressing the
Up
or
Down
buttons. When set as required press the
E
button to return to the sub-menu.
6.10.2 Calibration of internal references:
rEF
CAUTION
Do not attempt to recalibrate these
references unless you have adequate
test equipment and have read the
following instructions.
The
indicator
contains
two
references
representing 4 and 20mA. These references
are used in the 'SEt' function which enables
the indicator displays to be calibrated without
an external current calibrator. They are also
used in the 'C--P' function if the instrument is
programmed to display the input current when
the
P
push button is operated.
If the 'SEt' or
'C--P' functions are not used, it is not
necessary
to
calibrate
these
internal
references.
To calibrate the references select 'rEF' from
the sub-menu and press
P
which will result in a
'.004A' prompt being displayed. Adjust the
external current calibrator to 4.000mA and
again press
P
. The indicator will display 'Ent'
when the 4mA reference has been updated
and will then return to the '.004A' prompt.
Summary of Contents for ba326c
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