17
Trigger Mode
With the CHEM2000 or CHEM2000-UV-VIS and OOIChem Operating Software, you have two
methods of acquiring data. In the
No External Trigger Mode
(or Normal Mode), the spectrometer is
“free running.” That is, the spectrometer is continuously scanning, acquiring, and transferring data to
your computer, according to parameters set in the software. In this mode, however, there is no way to
synchronize the scanning, acquiring and transferring of data with an external event.
To synchronize data acquisition with an external event, the
External Software Trigger Mode
is
available. It involves connecting an external triggering device
!
!
!
!
to the spectrometer and then applying
an external trigger to the spectrometer before the software receives the data. In this mode, the
spectrometer is “free running,” just as it is in the Normal Mode. The spectrometer is continually
scanning and collecting data. With each trigger, the data collected during the integration period is
transferred to the software. All acquisition parameters, such as the integration period, are still set in the
software. You should use this mode if you are using a continuous light source and its intensity is
constant before, during and after the trigger.
!
!
!
!
In order for you to use the External Software Triggering option, it is imperative that you know the
specifications and limitations of your triggering device. The design of your triggering device may
prevent you from using the external software triggering mode as it is described here.
To use the External Software Trigger Mode:
1.
Supply a line from your triggering device to Pin 3 of the J2 Accessory Connector on the PC20000 to
provide the positive v5VDC to the spectrometer. (See figure for pin location.) We do not
advise using an outside source to supply the voltage, as it is based on a referenced ground and your
reference may be different from ours. Using Pin 3 to supply voltage ensures that the spectrometer
will receive the appropriate voltage for the trigger event.
2.
Supply a line from Pin 8 of the J2 Accessory Connector
to your triggering device. (See figure for pin location.)
3.
Set your acquisition parameters in the software.
4.
Select
Spectrometer | Spectrometer Configuration
from the menu and choose
External
Software Trigger
.
5.
Once you select
External
Software Trigger
, it will
appear on your computer that your spectrometer is
unresponsive. Instead, it is waiting for the trigger.
Activate your triggering device.
J2 (D-SUB-15) Accessory Connector (female)
Graph and chart display mode
If you choose
Spectrum Only
, spectra from one real-time spectrometer channel and up to 8 overlays
can be displayed in the graph area. If you choose
Spectrum & Kinetics
, spectra from one real-time
spectrometer channel and up to 8 overlays can be displayed in the in the top half of the graph area. A
kinetics chart monitoring values from up to 4 wavelengths and 2 of their arithmetic calculations can be
displayed in the in the bottom half of the graph area, if the
Chart Active
function is enabled.
Flash Delay
The value entered here sets the delay, in milliseconds, between strobe signals sent out of the
spectrometer. This function allows you to enable or disable the triggering of external strobes
through the spectrometer. You would only enter a value in this box if you were operating an
external strobe source. The CHEM2000 and CHEM2000-UV-VIS systems do not include a strobe
light source.
Color Temperature
This box allows you to enter the color temperature (in Kelvin) of your light source. In order to calculate
relative irradiance, the reference spectrum must be made in Scope Mode with a blackbody light source
of known color temperature. This data is necessary for the software to complete calculations for relative
irradiance measurements. For CHEM2000 users, your lamp has a color temperature of 3100 Kelvin.
(CHEM2000-UV-VIS users cannot make relative irradiance measurements because the light source that
comes with the system is not a blackbody source with a known color temperature.)
