Gage CompuScope 85GC, Hardware Manual And Driver Installation Manual

Page: 88 / 174

82 CompuScope 85GC
CompuScope 85GC triggering
CompuScope 85GC features state-of-the-art triggering.
The trigger circuit is identical to that of an oscilloscope. This way, a user can easily replace the Digital
Oscilloscope in his or her application with a CompuScope 85GC. A user can select the trigger source, trigger
level and trigger slope using software commands.
The user can software-select the trigger source from any one of the following:
•
Channel 1
•
Channel 2
•
External Trigger
•
Software Trigger
The selected trigger source is then compared to a trigger level set by an on-board DAC. An on-board, high-
speed comparator is used for this function, making it possible to trigger on narrow pulses or glitches that are
much shorter than the sample rate.
Each time the selected signal crosses the trigger level, the on-board triggering circuitry monitors it for the slope
selected by the user. When the appropriate slope is detected, a Trigger signal is generated.
Figure 55: Generation of a trigger signal
External Trigger amplifier
The External Trigger input also has oscilloscope-like 1 M
Ω
/ 20 pF input impedance.
Gage’s proprietary input-protection circuitry allows the FET stage to withstand voltages as high as
±
15 Volts
without causing any damage to the inputs.
Software-selectable attenuation of X1 or X5 on the External Trigger input allows input ranges of
±
800 mVolt
and
±
8 Volt, respectively.
TV Triggering
The CompuScope 85GC provides a TV triggering mode so that it may be triggered off of standard TV signals.
TV signal protocols supported are NTSC and PAL.
CompuScope 85GC allows triggering off of even or odd signal fields or off of any horizontal line which is
specified by a line number.