23
Repeat this procedure for each break-point, and
then return to the main menu by pressing E twice.
9.4.2 Calibration using internal references
This function enables the break-points to be
adjusted without the need for an accurate external
current source. Throughout calibration the
indicator input current may be any value between 4
and 20mA.
The accuracy of this method depends upon the
accuracy of the internal references which should
be calibrated periodically against a traceable
external current source with a resolution of at least
0.4µA. See section 6.7.2
The number of break-points required should first
be entered using the Add and dEL functions. In
both these functions the indicator initially displays
the current break-point and the total number of
break-points being used. e.g.
5 13
current total number of
break-point break-points
'Add' Add a break-point
Adds a new break-point before the
displayed break-point. The calibration
of existing break-points is not changed,
but the identification number of
subsequent break-points is
incremented.
'dEL' Remove a break-point
Removes the displayed break-point
and joins the preceding break-point to
the following break-point with a straight
line. The identification number of all of
subsequent break-points is
decremented.
'inPut' Defines the current at which break-
point occurs
Enables the required current at each
break-point to be defined without
having to input an accurate current to
the indicator.
'diSP' Defines display at break-point
Enables the indicator display at each
break-point to be defined.
Select 'SEt' from the main menu and press P once
to enter the 'Add' function, and again to reveal the
current and total number of break-points. Each
subsequent operation of the P push-button will
introduce an additional break-point. When adding
a break-point to a calibrated indicator, the insertion
position can be selected using the Up and Down
push-buttons.
The delete break-point function dEL operates in a
similar manner to the Add function described
above.
When the required number of break-points has
been entered, return to the sub-menu by pressing
E. The indicator will display 'Add' or 'dEL'
depending upon the last function used. The
required indicator display at each break-point can
now be entered, followed by the input current at
which each break-point occurs.
To enter the required display at any break-point
select ''diSP' from the sub-menu and press P
which will select the first break-point '0 n'. The
selected break-point can be changed using the Up
and Down buttons. When the required break-point
has been selected press P to reveal the existing
display. Use the Up and Down buttons and P to
move between digits set the revised display.
Press E to return to the sub-menu from which
another break-point can be selected. Repeat this
procedure for all the break-point displays to be
changed, and then return to the 'diSP' prompt in
the sub-menu by pressing E.
To enter the input current at which each break-
point occurs select 'InPut' from the sub-menu and
press P which will select the first break-point '0 n'.
The selected break-point can be changed using
the Up and Down buttons. When the required
break-point has been selected press P to reveal
the input current at which the break-point occurs.
Using the Up and Down buttons and P to move
between digits set the revised input current. Press
E to return to the sub-menu from which another
break-point can be selected.
Repeat this procedure for all the break-point input
currents to be changed, and then return to the
'InPut' prompt in the sub-menu by pressing E.
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