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The Mode Switch is a three position switch which controls the servo reset system.
MANUAL (MNL) The build-up time reduction control circuit is not active. The
piezoelectic voltage is reset and held at the center of its range.
AUTO The build-up time reduction control circuit is active. The servo
reset system automatically resets to the center of the
piezoelectric voltage range whenever the piezo voltage nears
the end of its range.
DISABLE (DSBL) The build-up time reduction control circuit is active, but the piezo
does not automatically reset when it reaches the end of its
range. Consequently, if the voltage to the piezo is at its limit,
the build-up time reduction circuit will not function properly.
As described in Section 1.1.4, the piezo’s voltage range is from -400 V to +400 V, with ³0 V
being the reset value. When the Mode Switch is set to AUTO the piezo automatically resets to 0
volts whenever the piezo voltage has scanned to within 50 volts of a limit (ie. ±350 volts ). If a long
experimental data run is being taken and it is noted that the piezo voltage is nearing the end of its
range, the AUTO reset can be disabled allowing the piezo to go to the full extent of its range
(±400V) by placing the Mode Switch in the DISABLE position.
3.1.5 Reset Indicator
This yellow LED is illuminated when the servo reset system is automatically resetting the
piezo to zero volts.
3.1.6 Reset BNC
This connector provides a low signal output during AUTO reset when the piezo has scanned to
a limit of its range and is being reset. The output is of the "open collector" type, meaning that it can
sink up to 250mA when in the low state.
This can be used to blank experimental data capture during the reset time over which the servo
electronics are reacquiring a "locked" condition (approximately 15 sec).
3.1.7 Frequency BNC
The frequency of the seed laser can be adjusted by applying a voltage to this BNC. Since good
overlap of the seed laser and host laser frequencies is necessary for proper seeding, if the seed laser
frequency is adjusted it also may be necessary to adjust the host laser frequency (via the Nd:YAG
rod cooling water temperature). The seeder's frequency is adjusted by applying an analog voltage to
this BNC, ranging from -10 V to +10V. This corresponds to approximately a ±10 GHz tuning
range.
3.1.8 Piezo BNC