[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: clock oscillators & cable issue (fwd)



Hall D Electronics:


Dear Fernando, and Gerard,

a lot of this emails we have been sending are wery informative. I think we
should put the discussion on the mailing list. either tracking or
electronics, what ever you think is better.

cheers elke



 ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
  )    `\                                                  -
 /    '. |                                                  +
 |       `,              Elke-Caroline Aschenauer            =
  \,_  `-/                                                    -
  ,&&&&&V         Jefferson Lab                                +
 ,&&&&&&&&:       HALL-D 12C / F381       121-A Atlantic Avenue =
,&&&&&&&&&&;      Suite 8                 Hampton, VA 23664      -
|  |&&&&&&&;\     12000 Jefferson Ave                             +
|  |       :_) _  Newport News, VA 23606  Tel.:  001-757-224-1216  =
|  |       ;--' | Mail:  elke@jlab.org    Mobil: 001-757-256-5224   -
'--'   `-.--.   |                                                    +
   \_    |  |---' Tel.:  001-757-269-5352                             =
     `-._\__/     Fax.:  001-757-269-6331                              -
            +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+

---------- Forwarded message ----------
Date: Wed, 06 Feb 2008 16:26:23 -0500
From: Gerard Visser <gvisser@indiana.edu>
To: Fernando J. Barbosa <barbosa@jlab.org>
Cc: "cmeyer@ernest.phys.cmu.edu" <cmeyer@ernest.phys.cmu.edu>,
     Elke-Caroline Aschenauer <elke@jlab.org>,
     Yves VanHaarlem <yvhaarle@ernest.phys.cmu.edu>,
     Simon Taylor <staylor@jlab.org>
Subject: Re: clock oscillators & cable issue

Hi Fernando,
	No, unfortunately I haven't yet had a chance to really measure the
crosstalk. I agree it is important. As you know it is a little painful
because it is a system with 25 inputs and 25 outputs, and all have to be
properly connected to get a correct answer. I think my plan to do so is:
	Make TDR measurements with an 18 m cable and the preamp board, verify
the 59.0 Ohm resistor value, and see whether there's any significant
difference between that and a 49.9 Ohm resistor w/ no ASIC, i.e., middle
position.
	Rig up 16 channels at the far end into the receiver board, and the
other 8 channels terminated somehow (possibly I'll wire over to a 2nd
receiver board, that would be best).
	Then pulse the ASIC and measure the crosstalk in terms of peak-height.
This should be done with the cable equalization applied (which is the
easiest thing to do, anyway), because we really want to know what is the
crosstalk of the whole system consisting of term+cable+term+equalizer.
	However of course I first need to tune the receiver/shaper board
equalizer circuit, it's a little different than I am planning now for
the ADC board. But just a few days of labwork. The values I picked
before (for the old cable & preamp) seem to do a decent job already.
	The crosstalk evaluation must include a study of the effects of the
pulser pair, as well as the signal pairs. E.g., what signal is induced
on the pulser pair from the output signals, is that a problem. Also,
what signal is directly induced on the signal pairs when the pulser pair
is pulsed, is that a problem. I will include these necessary tests.

	Gerard

Fernando J. Barbosa wrote:
> Hi Gerard,
>
> I really like these 3M connectors for the same reasons you mention plus
> the shielding connection. However, it is difficult to install them on
> the cable, especially without the proper tool. I am not sure if I
> mentioned this before but after talking to the rep, I learned that 3M
> can install these connectors on any cable we specify. Or we can
> outsource to some third party company, as we had planned.
>
> While on the subject of cable, have you had a chance to measure the
> crosstalk on the cable alone? I may have missed that report.
>
> Regards,
> Fernando