USER I/O CONNECTIONS
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Many CO2 lasers operating in applications requiring short gating pulses at repetition rates below 500 Hz
will exhibit some leading-edge overshoot regardless of the PWM frequency. This occurs because a
cooler lasing medium (the CO2 gas) is more efficient than a hotter one. This overshoot effect is more
pronounced at lower gating frequencies since the gas has a longer time to cool down between
Command signal pulses.
Marking/engraving operation
When the delay between the end of one PWM Command signal pulse and the beginning of the next
PWM pulse exceeds 200 microseconds (less than or equal to 5 kHz), F201 laser’s on-board tickle
generator sends a tickle pulse to maintain plasma ionization in the tube. Because the on-board tickle
generator cannot anticipate when the next PWM Command pulse will arrive; the tickle pulse (which
typically lasts for 2–6
μ
s depending on the laser) can effectively merge with a PWM signal that follows
closely afterwards. When the PWM pulse that follows is short, causing the tickle pulse to become a
significant fraction of the PWM pulse duration, then the tickle pulse effectively substantially increases the
length of the PWM pulse it has merged with. For subtle marking applications on sensitive, low threshold
materials this lengthened PWM pulse may affect mark quality.
While this situation can occur when using PWM Command signal frequencies of 5 kHz and less, it is im-
portant to note that it isn’t the Command signal frequency itself that is the determining factor but rather
this behavior happens only when the off time between PWM pulses exceeds 200 microseconds.
User I/O connections
The User I/O connections section includes subsections:
•
User I/O connection summary
•
Input/output signals
•
Sample I/O circuits
The PWM Command signal and all input/output (I/O) control signals are connected to the User I/O port,
a 15-pin female D-type subminiature connector, on the i401’s rear panel. Figure 3-5 below illustrates the
pin arrangement of the User I/O connector.
Caution: Possible Equipment Damage
Turn off DC power before installing or removing any plug or cable from the User I/O connector.
Ensure that user connections are made to the appropriate pins and that the appropriate signal levels
are applied. Failure to do so may damage the laser.
