8
6. CALIBRATION
The BA307C and BA308C will be supplied
calibrated as requested at time of ordering. If
calibration is not requested, the indicator will be set
to display 00.0 with 4.000mA input, and 100.0 with
20.000mA input.
Both instruments are conditioned and calibrated by
plug-in links and two multi-turn potentiometers.
The potentiometers are accessible through holes in
the rear panel, but the rear panel must be removed
to gain access to the plug-in links - see Fig 6.
For maximum accuracy, indicators should be
calibrated using an external traceable current
source with an accuracy greater than 4
A.
However, when verification is not required the
indicator can be fitted with an optional internal
calibrator which allows rapid calibration without the
need for external instruments. See section 8.3 for
details.
6.1 Zero adjustment
Zero is defined as the number displayed by the
indicator with a 4.000mA input current, and may be
adjusted between -1000 and 1000. The zero
potentiometer has two ranges, 0 to 500 and 500 to
1000. Zero polarity is defined by the position of
the suppression / elevation links which are shown
in Fig 7.
Fig 6 Removal of rear panel
Fig 7 Position of plug-in calibration links and potentiometers
