2.1 Front panel controls 13
FAST GAIN Ten-turn fast servo proportional gain; from −10 dB to +50 dB.
FAST DIFF/FILTER Controls the high-frequency servo response. When set to “OFF”, the
servo response remains proportional. When turned clockwise, the
differentiator is enabled with the associated corner frequency. Note
that decreasing the corner frequency increases the action of the
differentiator. When set to an underlined value, the differentiator is
disabled and instead a low-pass filter is applied to the servo output.
This causes the response to roll-off above the specified frequency.
DIFF GAIN High-frequency gain limit on the fast servo; each increment changes
the maximum gain by 6 dB. Has no effect unless the differentiator is
enabled.
2.1.4 Lock controls
GAIN LIMIT Low-frequency gain limit on the fast servo, in dB. MAX represents
the maximum available gain.
ERROR OFFSET DC offset applied to the error signals when INPUT mode is set to ∆.
Useful for precise tuning of the locking point or compensating for
drift in the error signal. The adjacent trimpot is for adjusting the
error offset of the slow servo relative to the fast servo, and may be
adjusted to ensure the fast and slow servos drive towards the same
exact frequency.
SLOW Engages the slow servo by changing SCAN to LOCK. When set to
NESTED, the slow control voltage is fed into the fast error signal
for very high gain at low frequencies in the absence of an actuator
connected to the slow output.
FAST Controls the fast servo. When set to SCAN+P, the proportional feed-
back is fed into the fast output while the laser is scanning, allowing
the feedback to be calibrated. Changing to LOCK engages the full
PID control action.
To Next Page
Loading...