PMS-300 PMS-400 800 MHz Gated Photon Counters / Multiscalers

Measurement Control
Mode
Channel rates
The results of the counters within the specified collection time are displayed as bars. If 'Repeat' is
set the measurement is repeated in intervals of 'Repeat Time' and the current results are continuously
displayed on the screen. Depending on the 'Trigger Condition' the recording can be started either
immediately after finishing the last collection time interval (Trigger Condition 'none') or by the next
rising or falling edge of the trigger pulse. The 'Channel Rates' mode is useful to test and to adjust the
measurement setup before the final measurement is started.
Multiscaler
In the multiscaler mode the counter results of subsequent collections time intervals are stored in
subsequent memory locations. The results represent the input pulse density versus time, i.e. the
waveform of the measured light signal. The time per curve point can be as short as 250 ns. The
effective collection time per curve point is 50 ns shorter, because 50 ns are required to read the
counters and to store the results in the memory.
Depending on the 'Trigger Condition' the recording can be started either by the software 'Start'
command (Trigger Condition 'none') or by the rising or falling edge of the trigger pulse. If the step
motor controller is used and the trigger condition is different from 'none' the trigger action depends
on the defined step motor actions. As long as no step motor action is defined 'After each Point' (see
'Stepping Device Configuration') the trigger starts the recording of a complete curve or a complete
sweep (if 'Accumulate' is active). With a step motor action 'After each Point' each collection time
interval is started by a trigger pulse. This allows the synchronisation of the stepping action with a
pulsed light source.
If 'Accumulate' is set several signal periods are accumulated. In this case the recording is restarted
with the next trigger pulse after the end of the previous recording and the obtained counter results
are added to the current memory contents.
The whole measurement sequence is repeated if the 'repeat' button is pressed. In this case a
repetition time ('repeat after ...') can be specified. If the repetition time is longer than the overall
recording time the subsequent measurements start in intervals of the repetition time. Otherwise the
next measurement is started immediately after the previous one is finished.
Under 'System Parameters' / 'Stepping Device Configuration' / 'Action' step motor actions can be
defined in several places of the measurement sequence. Therefore, with the optional step motor
controller STP-240 a lot of modifications of the measurement sequence are possible. With a step
motor action after each curve the dependence of the waveform of the light signal on a spatial
parameter or the wavelength is obtained. If a step motor action is defined after each curve point,
instead of a waveform a spatial dependence of the intensity or a spectrum is recorded.
Event Mode
In the event mode the incoming detector pulses are counted for the selected time intervals. When the
current collection time interval is over the counter results are compared to the 'Event Threshold'
value. If the result is greater than the event threshold value it is stored together with the time since
the start of the measurement.
The actual collection time is 50 ns shorter than the parameter ‘Collection Time’ because some time
is deeded to compare and store the result. The measurement stops when a number of events
specified by ‘Points per Curve’ was recorded.
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