Table of Contents
Advertisement
MSM+ HB
16.3.4
Examples for trigger operation
Example 1: fixed integration time
With these settings, the device detects the second laser pulse after the trigger is released. Depending on
how precisely it can be triggered, the integration time can also be varied.
Laser parameter
Pulse duration:
50 ns
Pulse frequency:
1 kHz
Example 2: very long pulse duration
In this example, the first 12 µs of the laser pulse are not measured.
Laser parameter
Pulse duration:
1 ms
16.3.5
Summary
If the laser is pulsing at a high frequency (> 500 Hz) or if the pulses last a long time (> 1ms), it is best to mea-
sure with the automatic integration time control. This makes it possible to vary or optimize the integration
time during a caustic measurement.
For the long pulse duration, choose the attenuation so that the integration time is smaller than the pulse
duration even outside of the focal point.
When the pulse frequency is very high, however, the attenuation must be chosen so that enough laser pulses
are integrated during the measuring cycle. If too few pulses occur during an integration time, the number of
photoelectrons will change too much with each pulse. The regulating routines of the LaserDiagnosticsSoft-
ware LDS will then lead to measurements with signal levels that are statistically too high.
It is important to make sure that the integration time is never shorter than the pulse pauses. If this is the
case, it will no longer be possible to perform an untriggered measurement properly with the device.
So it sometimes makes sense to set the attenuation so that exactly one pulse is enough to expose the
sensor at the focal point. You can then measure a caustic with a fixed delay and an integration time set when
the focus was measured. The dynamic of the CCD sensor is sufficient to measure the entire caustic with an
acceptable S/N ratio.
Revision 00 EN - 02/2022
Device settings
Delay:
950 µs
Integration time:
100 µs
Trigger channel:
external trigger signal
Device settings
Delay:
12 µs
Integration time:
1 ms
Trigger channel:
internal trigger signal
115
Advertisement
Table of Contents
