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Appendix B
External Triggering
Overview
The USB2000+ supports four triggering modes, which are set with the Trigger Mode command. Details
of each triggering mode follow.
Normal (Free Running)
In this mode, the USB2000+ uses the user-defined integration clock and continuously scans the CCD
array. All of the signals described in the previous section are provided by the spectrometer to the CCD
automatically based on the integration time selected in the software by the user.
External Software Trigger
In this mode, the ExtTrigIn signal acts as an enable switch. If ExtTrigIn is kept HIGH, the USB2000+
will acquire spectra as if it was in the normal free running mode. If ExtTrigIn is kept LOW, the
USB2000+ will not acquire spectra.
External Hardware Trigger
On the USB2000+, Ocean Optics has altered the functionality of the External Hardware Trigger function
and reprogrammed the Single Strobe signal function. These alterations of the USB2000 enable you to
operate in the Variable Delay Mode without the presence of an external trigger signal. The USB2000+
will simulate the signal to trigger the appropriate circuitry in the spectrometer.
The table below summarizes the capacity of the USB2000+ in Variable Delay Mode:
Parameter Value in Normal Acquisition Mode Value in Variable Delay Mode
Integration time User controlled 5 ms fixed
Strobe delay
0 µs 2 – 511 µs + 3 µs
Jitter < 25 ns < 25 ns
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