OPERATIONAL FLOWCHART
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115
Symptom:
The SHT LED is flashing continuously because of a No-Strike condition as indicated by the
following status LEDs and I/O states:
Possible Causes:
•
A No-Strike condition has occurred, possibly due to cold environmental conditions that may
prevent the gas from breaking down into a plasma state. When this occurs while a PWM signal is
applied, laser output is limited to a PWM duty cycle of approximately 5%.
Apply tickle pulses or a PWM Command signal (< 5% duty cycle) for 30 to 60 seconds. When the gas
breaks down into a plasma state, the laser will recover and begin lasing at the commanded duty cycle
without cycling DC power.
Symptom:
A shutter closed condition is indicated by the following status LEDs and I/O states:
Possible Causes:
•
No Shutter Open Request signal on Pin 10 of the User I/O connector.
Check to see that a positive or negative voltage in the range of ±5–24 VDC is applied to Pin 10, Shutter
Open Request, with respect to Pin 11, Input Common, on the User I/O connector (refer to User I/O con-
nections in the Technical Reference section for details). If your system does not provide a Shutter Open
Request signal, wire a male DB-15 connector to the User I/O connector so that Pin 11 (Input Common) is
jumpered to Pin 12 (Auxiliary DC Power Ground) and Pin 10 (Shutter Open Request) is jumpered to Pin 4
(+5 VDC Auxiliary Power).
When a Shutter Open Request signal is applied to the laser, it takes approximately 30 ms for the electro-
mechanical shutter to fully open. Although tickle signals are applied to RF circuitry during this interval,
PWM Command signals are inhibited until the shutter is fully open. When the Shutter Open Request
signal is removed from Pin 10, PWM Command signals are inhibited immediately; however, the electro-
mechanical shutter takes approximately 120 ms to fully close.
