11
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 display at 20mA, press the
Up
button
which will cause the indicator 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 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 all the digits have been adjusted press
E
to
enter the new span. The indicator 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 primary element to indicator
display e.g. when the indicator is displaying the
output from a resistance thermometer transmitter.
6.6 Calibration of display using internal
references: SEt
This function enables the zero and span of the
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
6.7.2
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 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 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 'SPAn' prompt followed by
E
to return to the menu.
6.7 Conditioning sub-menu: Cond
This sub-menu allows the mains (line) frequency at
which the indicator has maximum ac rejection to
be selected and the two internal references to be
calibrated. These functions are contained in a
sub-menu to minimise the possibility of inadvertent
adjustment. To gain access to the sub-menu
select 'Cond' from the main menu and press
P
.
The indicator will display 'SurE' to warn that
changing the parameters in the sub-menu will
change the indicator display. Pressing
P
again will
give access to the sub-menu, or pressing
E
will
return the indicator to the main menu.
6.7.1 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
changed by pressing the
Up
or
Down
buttons
followed by the
E
button to return to the sub-menu.
6.7.2 Calibration of internal references: rEF
The indicator contains two references representing
4 and 20mA. These references are used in the
'SEt' function which enables the indicator display to
be calibrated without an external current calibrator.
They are also used in the 'C--P' function when the
P
push-button is programmed to display the input
current in the display mode. If neither of these
functions is to be used, it is not necessary to
calibrate the internal references.
To calibrate the references select 'rEF' from the
sub-menu and press
P
which will result in a
'0.004A' 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.
To re-calibrate the 20mA internal reference, press
the
Up
button which will cause the indicator to
display '.020A'. Adjust the external current
calibrator to 20.000mA and again press
P
. The
indicator will display 'Ent' when the 20mA
reference has been updated and will then return to
the '.020A' prompt. Two operations of the
E
button
will return the indicator to the main menu.
