OPHIR vega User Manual page 51

Figure 4.6
Thermopile Energy Screen
4.5.2. Measurement
To measure energy of a single pulse, set up as above and
fire the laser. The display will go blank while the energy
is being integrated. After 2-4 seconds, the correct energy
will be displayed. When the Vega is ready to measure a
new pulse, "READY" will appear on the screen and flash
on and off. (See
Figure ). The next pulse will automatically blank the
4.6
screen, and the new value will be displayed. If you fire
another pulse before "READY" appears, the reading may
be inaccurate or may not be displayed.
4.5.3. Minimum Energy Threshold
If the Vega is used in a noisy environment or where there
is a high level of background thermal radiation, the
instrument may trigger spuriously on the noise or
background radiation. It would then fail to measure the
intended pulse. Since there is always some degree of
noise or background radiation, the instrument is designed
not to respond to pulses below some preset minimum
size. This "Minimum Energy Threshold" is typically set to
0.3% of full scale of the selected range. If this level is
found to be too sensitive for the user's particular
environment, it may be altered by the user. The threshold
should not, however, be raised higher than necessary.
This will cause a degradation in the accuracy of energy
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