Andor Technology iXon Ultra 897 User Manual page 125

CCD has been supplied with a built in shutter, the TTL pulse is factory set to
high. Changing this setting will affect operation of the shutter.
• If you click the TTL Low button the system will cause the output voltage from
the controller card to go 'low' to open the shutter.
Check the documentation supplied by the shutter manufacturer to see whether your
shutter opens at a high or a low TTL level.
The shutter pulse is fed from the Shutter out pin on the back of the camera.
Shutters take a finite Time to open or close: this is sometimes called the
Transfer Time. The documentation supplied by the shutter manufacturer should
indicate the Transfer Time you can expect from your particular shutter. In the case
of a CCD detector, the Transfer Time is used principally to give the shutter enough
time to close, before background data are acquired. The system ensures that a period
of at least the duration of the Transfer Time elapses between the shutter output signal
entering the 'closed' state and commencement of background data acquisition.
As the iXon contains a Frame Transfer CCD device, a shutter may not be required
for most applications. If a shutter is fitted but not required for the experiment, then
set it to permanently open, and Time to 0. This will allow the system to operate at its
optimum rate. If a Bg is required then close the shutter using Permanently Close,
take Bg, and reopen.
Let us look at the Transfer Time in the context of the Andor system. By default,
the value you enter in the Exposure Time text box on the Setup Acquisition dialog
box determines the length of time the shutter will be in the open state. However, to
accommodate the Transfer Time, the rising edge of the Fire output signal follows the
start of the shutter open state after a delay, equal to the value you enter as Time to
open or close. You should set this value to the Transfer Time of your shutter.
The system also automatically adds the Transfer Time to the end of the acquisition
SHUTTER CONTROL
Time for shutter
to open or close
Section 4 . 11
Page 125