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Chapter 1. The electronics

The other output from the splitter will go into a discriminator. This could be either a leading edge or a

constant fraction discriminator. The job of the discriminator is determine when a signal has occurred and

to put out a logic signal when it does. The discriminator will have a threshold knob, be sure that the

threshold is set above any background noise that may be present so that the discriminator only trips on

the pulser signal. It will be useful to look at the both the logic pulse and the signal from the ampliﬁer at

the same time when setting the threshold value. Figure 1-4 shows what you will see.

Figure 1-4. Ampliﬁed Signal with Logic pulse

When the threshold is set to a reasonable level, connect one of the dis- criminator outputs to the start of

one channel of your gate and delay gen- erator. The gate and delay generator will generate a gate when it

receives a logic signal from the discriminator. When looking at the signal from the ampliﬁer and the gate

at the same time on the scope, the signal pulse should fall within the gate as seen in ﬁgure 1-5. If the gate

is occurring too early you can use the gate and delay generator to delay the gate or to make the gate last

longer. If the gate is too late you need to delay the signal pulse, that can be done using a delay module, or

by adding cable delay. When you are happy with the gate timing, plug it into one of the LEMO

connectors on the CAEN V785 labeled gate, put a 50 Ohm terminator in the other one.

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ADC 400F Handbuch Seite 9