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Entry  Fri Dec 13 10:37:18 2013, Dmitry Hits, input protection in DRS4 evaluation board 
    Reply  Fri Dec 13 11:37:58 2013, Stefan Ritt, input protection in DRS4 evaluation board 
Message ID: 318     Entry time: Fri Dec 13 11:37:58 2013     In reply to: 317
Author: Stefan Ritt 
Subject: input protection in DRS4 evaluation board 

Dmitry Hits wrote:

Last month I was using a DRS4 evaluation board to digitise the signal from the charged particles in piM1 beam line at PSI. The beam in piM1 is a mixture of pions with a small percentage of protons. Pions are close to minimum ionising and were producing the signals on the order of 250 mV (Landau distributed). The protons at this momentum (250 MeV) are not minimum ionising  and produced much higher signals ( I could not exactly measure them because they were of scale for the DRS4 board). The pulses were on the order of 0.5 usec long. At low rate (~1kHz) the board was able to handle them, but when I turned the rate of particles to about ~300 kHz, the channel went flat. My question is whether the evaluation board has some type of input protection that would be possible to replace? Or does that mean that I have burned the input of the DRS4 board itself? Other channels behaving normal.

As written in the manual, the board withstands +-20V pulses which are shorter then 2 usec, and a DC input of +-10V. If your pulses are bigger or longer, you will kill the input buffer chip, which needs to be re-soldered. You can check if the channel is broken by applying a periodic signal of known amplitude (e.g. a 100 mV 1 MHz sine wave). If the measured amplitude differs significantly from the others (like only half the amplitude) or is completely flat, you burned the input stage. When you are next time at PSI you can bring the board and we can then fix it.

/Stefan

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