HP 212A - Operation

from time to time if necessary.
See Section IV, Maintenance, regarding
the adjustment of these controls.
The length of the main pulse is essentially independent of the other controls
except that the pulse length will tend to change slightly as the repetition
sate is changed especially above repetition rates of 1 kc.
The internal repetition rate generator is a rnultivibrator adjustable over
the range from 50 to 5000 cycles /set. Calibration of this cohtrol should,
in general, hold within f 2 570, but when accurate repetition rates are desired,
it is preferable to use an external oscillator to drive the pulse generator.
The Model 2L2A can be synchronized from external pulses having at least a
5 volt amplitude and a rise time in the order of a microsecond or two. If
it is desired to synchronize from a sine wave source, it is necessary to
use a wave shaper of some sort to increase the rise time of the synchroniz-
ing voltage.
The unit synchronizes very well from an @ Model 21 1A
Square Wave Generator. Another typical waveshaper which may be used
for a sine wave input is show in Figure 2-1.
It is important that the Model 212A not be driven at a pulse rate in excess
of 5000 cycles /sec. Performance at this end of the range is limited mainly
by the duty cycle of the thyratrons,
There is practically no limit to the re-
petition rate at the low frequency end provided the synchronizing pulses
have a time-of -rise in the order of one
or two microseconds,
Since the unit is limited by duty cycle at high repetition rates and long pulse
widths,- there is a tendency for the amplitude to be affected by repetition
rates especially when the repetition rate is above 1000 cycles/sec and when
the pulse width is at the maximum value. However, compensating circuits
have been incorporated in the unit to minimize these amplitude variations
and for most purposes they are not serious.
2-8 OPERATION OF PUISE POSITION CONTROL
The PULSE POSITION control is designed to adjust the main pulse timing
around the SYNC OUT timing. This control will set the main pulse ahead
of the sync out by approximately 10 microseconds or after the sync out by
approximately 100 microseconds.
This control is not calibrated as its main
use is to position the main pulse on an oscilloscope screen.
This pulse
position will tend to be affected to some extent by the pulse rate.
This con-
dition is normal and should cause no serious difficulty under normal operat-
ing conditions.
See important precaution given at the end of paragraph 2-4.