12
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
4/20mA output from a resistance thermometer
transmitter.
6.6 Calibration using internal reference:
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 beenadjusted
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.
The accuracy of the internal references, and hence
the display accuracy, will depend upon the
accuracy of the external current source. With a
maximum span of 20000 the indicators have a
display resolution of 0.8µA, we therefore
recommend that the accuracy of the external
current source used for calibration is greater than
0.4µA.
To Next Page
Loading...
Need help?
General
