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V1682OPMA.doc
17 February, 2005
8. CALIBRATION
This section describes how to calibrate the unit as it is done in the factory. The V1682 and its modules
do not contain any potentiometers, but like most equipment with analogue parts still needs to be
calibrated. Normally this calibration is done in the factory and should not need to be repeated in the
field but this section describes the procedure and is included for completeness.
High quality, calibrated test equipment should be used for this calibration. Note that it is not possible to
return to the pre-calibration settings other than by making a note of the values and re-entering them.
8.1 SET-UP
There is a separate Main Level Menu for Calibration and this should be used throughout. The first sub-
level menu is
CALIB > Cal Mode
, which is used to set the unit into a known state for calibration. The
options available are ‘
Cal On
’ and ‘
Cal Off
’.
The calibration mode must be turned ON before any parameter can be adjusted. The calibration mode
will be turned OFF in one of four ways:
1. Manually on the
CALIB > Cal Mode
menu.
1. By going up to the Top Level Menu
2. By re-powering the unit.
3. By letting the display timeout and go to sleep mode.
When the calibration mode is on then the unit will automatically set up the required conditions in the unit
as you enter each sub-menu. For example if you go into the CntrFreq sub-menu the unit will
automatically go into free run. Similarly if you go into a DAC calibration menu it will produce tone onto
that channel. For obvious reasons this should not be done on a unit that is being used On Air.
8.2 FREE-RUN
FREQUENCY
The V1682 has a voltage controlled crystal oscillator which is usually locked to the external video
reference or to the input video. However if there is no input or reference then it will free-run and this free
running frequency should be set. The oscillator on the V1682 is not accurate enough to be used as a
frequency reference but nevertheless should be set close to the ideal so that any succeeding SDI
equipment will be able to lock to its output, and so that when in free run it will only drift slowly away from
its starting reference.
To calibrate the frequency set the unit into Free Run by turning Cal Mode ON and selecting the
CntrFreq
sub-menu.
Now monitor the clock frequency on TP 50 (Issue B and C PCB), or compare the output picture
movement on a monitor with an accurate external reference and adjust the frequency in the
CALIB >
CntrFreq
menu.
The setting is stored on the unit in non-volatile memory, and should not need regular adjustment.
