technical reference
39
Synrad
Series 48Series 48
Series 48Series 48
Series 48 operator’s manual
Controlling laser power
The Controlling laser power section includes subsections:
■ Control signals
■ Operating modes
Control signals
Much of the information provided in this section describes the use of a SYNRAD UC-2000 Universal
Laser Controller to provide PWM Command signals to the Series 48 laser. If using an alternate method
of laser control, thoroughly review this section, Controlling laser power for an understanding of the signal
requirements necessary to control SYNRAD Series 48 lasers. For more information about UC-2000
operation, please consult the UC-2000 Laser Controller Operator’s Manual.
Tickle pulse
All Series 48 lasers require a 1 µs ‘tickle’ pulse delivered at a 5 kHz clock frequency from the Controller.
Tickle pulses pre-ionize the laser gas to just below the lasing threshold so that a further increase in pulse
width adds enough energy to the plasma to cause laser emission. This tickle signal causes the laser to
respond predictably and almost instantaneously to PWM Command signals, even when there is consider-
able delay (laser off time) between applied Command signals. Series 48 lasers contain a precision pulse
stretching circuit that is preset to accept a 1 µs ±20% no-lase, tickle pulse. Lase threshold is factory-
preset for 3 µs ±0.5 µs based on a PWM and tickle frequency Command input of 5 kHz.
The UC-2000 (or FH Series marking head) does not produce tickle pulses continuously, but generates
them only when the PWM Command signal is low. Tickle pulses are sent one tickle period, 200 µs, after
the falling edge of a PWM Command signal pulse. Figure 3-6 illustrates tickle pulse parameters.
Figure 3-6 Tickle pulse waveform
5 VDC
0 VDC
1 µs200 µs
A 1 µs tickle pulse at frequencies greater than 5 kHz may cause unintended lasing. Special care must be
taken to maintain plasma ionization without lasing at tickle frequencies greater than 5 kHz. If sending
1 µs tickle pulses at 5 kHz, PWM signals can be sent at an independent, higher frequency but must go to
near zero (< 1%) duty cycle to ensure laser turn-off.
Caution
possible
equipment
damage
Applying PWM Command pulses directly to the laser without first
sending tickle pulses, will cause unpredictable laser emission,
degrade optical rise time, and may lead to RF Driver failure.
To Next Page
Loading...
