User manual

Installation Procedure
ComTec GmbH 2-14
but in the map display they will show up on the base of x- and y-axis (zero) since the respective
other ADC is read as a 'ZERO'.
Start data acquisition with the START button
. Depending on your signals spectra are shown.
End data acquisition by a click on STOP
.
2.6. Basic Usage of the RealTimeClock Option
To familiarize with the usage of the 48 bit RealTimeClock / Timer / Counter option a simple
experiment is setup. The intention is to measure the arrival time of single ADC events relatively to
a start (trigger) signal like it might be done in Time-of-Flight or similar experiments. To do so a
variable delay is used to shift analog output pulses relatively to the TTL trigger pulse that on the
other hand resets (reloads) the 48 bit counter via the AUX 1 input. Thus, in terms of TOF, the
trigger signal acts as start and the ADC deadtime signal as stop input. The delay time is then
measured with a resolution of 50ns and a time spectrum of the very ADC is accumulated.
First, ADC 1A is defined as a SINGLE mode ADC (ref. Figure 2.20). Now the RTC / Timer /
Counter is set to reload (restart) with the auxiliary input AUX 1 (ref. Figure 2.21). The timer value
capture command is derived from ADC 1A DEADTIME signal (ref. OR-ed DEAD of ADC 1A in
Figure 2.21). And, last but not least, timestamps must be inserted into the datastream to transfer
the corresponding time and ADC data together. The preset value is not importent in this case but
must be at least greater than the desired time range (or zero which will automatically change to
the maximum value). For the count source 20MHz is selected to use the internal 50ns crystal
clock.
Take care that the AUX 1 interface is used as input (ouput disabled – ref. Figure 2.22). Since the
here used analog pulser triggers on the falling edge the AUX 1 input polarity is 'active high' to
reload the timer when the TTL signal is high and let the timer free run when it is low.
To visualize the timing relationship a spectrum is defined that shows the arrival time on the x-axis,
the adc pulse height on the y-axis and the countrate in z-direction (ref. Figure 2.23). Also a one
dimensional spectrum is defined (set ADC range to 1) to show just a time spectrum (projection
onto the x-axis).
In Figure 2.24 the resulting spectra can be seen. Watching the map display (window (1))
amplitude variations show up as vertical lines whereas delay time variations result in horizontal
lines. Window (4) is the corresponding three-dimensional view, window (3) the pulse height
analysis and (5) the time spectrum.
Figure 2.19: Basic RTC Experiment