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I'm performing tests of the detector's breakout electronics. These are printed circuit boards that will take signals from inside an ionization detector to the rest of the data acquisition apparatus.

The key component of these circuits is a capacitor, upon which charge is collected which induced a voltage across the capacitor. This charge is the result of ionization events inside the detector, and specifically the ionized electrons being collected by wires inside the chamber.

I have a BNC Model BH-1 pulse generator (link) and I have tried hooking it up directly to the circuit boards in question. The output from the boards, viewed on an oscilloscope, is signal-like, and responds to manipulation of the pulse generator dials, as one would expect. But it's heavily warped by the interference of the two involved RC circuits.

The pulse generator doesn't simulate the expected charge collection correctly. I want it to produce a charge buildup on the capacitor as a real event inside the detector would. Perhaps I require additional circuit components to make this work? Or I don't understand the problem myself in full detail? Any help or identification of my points of ignorance would be appreciated.

sam porter bridges
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    How much capacitance? What type of plate amplifier? – Andy aka Jul 04 '17 at 14:41
  • It's a 47 pF capacitor. Plate amplifier? The only amplification involved would be a pre-amplifier stage that is not involved in this testing. – sam porter bridges Jul 04 '17 at 15:20
  • Looks like the BH-1 is there to help calibrate systems. But that doesn't mean the BH-1 was designed for the systems you actually have. Has it been used in the past? – jonk Jul 04 '17 at 17:32
  • What is the interface to the 47 pF capacitor that collects the charge? – Andy aka Jul 04 '17 at 18:04

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Generally, the simulation of charge collection is achieved by passing of the test pulses through a very small capacitor (<1pF) to the detector.

q-amp test input

alpo
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