Re: Contact Information for Electronics

["Fernando J. Barbosa" <barbosa@jlab.org>]

Hi Gerard,

    Yes, we really need to have a table like the one you suggest. It is 
especially important to know the maximum lengths given the constraints 
on shaping, gain and dynamic range for both the fADC-125 and the ASIC.

Regards,
Fernando



Gerard Visser wrote:
> Hi Fernando,
>     Ah, ok, this makes sense, it is a good plan. I would intend to be 
> leaving them (CDC) with a shaper board properly set up for the new 
> preamp. So they should then be in a position to use real cable length.
>     I'm cc'ing Joe and the list here, about the cable lengths... Is 
> the following known yet:
>     What lengths of cable are expected for the FDC in what quantities 
> each?
>     What lengths of cable are expected for the CDC in what quantities 
> each?
>     All that I know so far is that the _maximum_ FDC cable is 21m (69 
> feet), and now also I learn same _maximum_ is anticipated on CDC (I'm 
> surprised by that a little bit, given what I think I remember of the 
> floorplan). It would be good to get to a table like this:
>
> FDC cathode
> -----------
> N1 cables length 21 m
> N2 cables length 19 m (or whatever)
> N3 cables length 16 m (or whatever)
>
> FDC anode
> ---------
> similar
>
> CDC
> ---
> similar
>
>     It is clear that equalization is needed to get the signals out of 
> these cables... To design it we need to get a firm handle on the 
> lengths. This _can_ be deferred - but I probably would prefer to 
> sketch out some actual design. For this at least I'd like to know the 
> range of lengths and how many different lengths. (Hopefully the range 
> is small enough we don't really need different values of equalization.)
>
>     Gerard
>     
>
> Fernando J. Barbosa wrote:
>> Hi Gerard,
>>
>>     The 10 ft cables are just for looking at signals out of the cards
>> with a scope or for similar probing - just to get them started. The
>> cable will be spliced at one end and have the ERNI connector on the
>> other. Elke suggested a small length of cable as they don't have any
>> shaping boards or your fADCs. I think it would be just useful for
>> debugging any noise issues and getting familiar with the cards.
>>
>>     I suggest you look at the signals with the long cables, perform the
>> shaping and then tell them what they need. They really need a shaping
>> board before they can perform any useful tests, I think. I can then send
>> a long cable. Joe still believes 65 ft should be enough.
>>
>> Regards,
>> Fernando
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