[Halld-tracking-hw] Tracking Meting Tomorrow
Fernando J. Barbosa
barbosa at jlab.org
Fri Apr 15 14:48:24 EDT 2011
Hi Naomi, Gerard,
I have configured and tested the preamps as I described earlier (should
have a short doc later) and they are shipping to each of you today via
FedEx. You should have them on Monday.
Best regards,
Fernando
Naomi Jarvis wrote:
> Great! That should work nicely.
>
>
> Thanks,
>
> Naomi.
>
>
> On Thu, April 14, 2011 9:29 am, Fernando J. Barbosa wrote:
>
>> Hi Naomi,
>>
>>
>> Yes, the changes (removing terminating resistors at the output of the
>> preamp) will be on the preamp. We still need the modified HVB to attenuate
>> the charge into the ASIC. So, the CDC will have the preamp configured with
>> low gain (~0.6 mV/fC - the setting you have now), no terminating resistors
>> on the preamp output, modified HVB and fADC125. One fADC125 will be used
>> with both the CDC and the FDC and as it is now.
>>
>> 14-bit ADCs are not on the plans.
>>
>>
>> Best regards,
>> Fernando
>>
>>
>>
>>
>> Naomi Jarvis wrote:
>>
>>
>>> Hi Fernando,
>>>
>>>
>>> you do mean the preamp and not the HVB, right? I already collected
>>> cosmics with the unmodified HVB (without the attenuators) to see if the
>>> resolution would be any different, it does look better (pics on the
>>> wiki, tracking mtg agenda) but we do still need to use the modified HVB
>>> to fit the dynamic range we want into the preamp.
>>>
>>> What about using 14-bit ADCs ?
>>>
>>>
>>> Naomi.
>>>
>>>
>>>
>>> On Apr 13, 2011, at 7:47 PM, Curtis A. Meyer wrote:
>>>
>>>
>>>
>>>
>>>> Hi Fernando -
>>>>
>>>>
>>>> please do send us one of these preamp cards -- thanks .. curtis On
>>>> 4/13/11 5:22 PM, Fernando J. Barbosa wrote:
>>>>
>>>>
>>>>
>>>>> Hi Gerard,
>>>>>
>>>>>
>>>>> OK, I will send you two preamps (CDC and FDC).
>>>>>
>>>>>
>>>>> There is an easy way to double the pulse amplitude at the input of
>>>>> the ADC which is to remove the back-terminating resistors on the
>>>>> preamp card. This would not change the preamp response . This change
>>>>> would not require any changes to the fADC125 and one version would
>>>>> still fit both detectors as this is already the consensus at JLab. I
>>>>> can send a preamp to Naomi in this configuration for tests.
>>>>>
>>>>> Best regards,
>>>>> Fernando
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Gerard Visser wrote:
>>>>>
>>>>>
>>>>>
>>>>>> Hi Fernando,
>>>>>> Thanks, I will change the gain setting as you say.
>>>>>> Could you please still send me another board in CDC
>>>>>> configuration? First of all this one is set for cathodes and I
>>>>>> might not have enough 0402 jumpers to convert to anodes operation,
>>>>>> and secondly this board has apparently all channels dead on the
>>>>>> middle ASIC and I worry perhaps could have an abnormal response on
>>>>>> the others (I don't know what the cause of the trouble is). In any
>>>>>> case, having two boards to be able to confirm the measurements on
>>>>>> the second unit, I think will be a good idea. If you have 'plenty'
>>>>>> then please also send one in FDC cathode configuration (same
>>>>>> reasons). I have updated my slide with a 2nd one showing the
>>>>>> waveforms at the ADC output terminals. With the caveat this is as
>>>>>> you say for quite the wrong gain selection on the ASIC, the
>>>>>> results of this test look to me to indicate the linearity is
>>>>>> really worse than it looks on the ADC125 view, the maximum
>>>>>> reasonably linear pulse height is about 43% of full scale on the
>>>>>> ADC. We'll have to see how this looks with
>>>>>> the correct gain setting on the ASIC. My updated slides are here
>>>>>> http://npvm.ceem.indiana.edu/~gvisser/GlueX/ADC_scale.pdf
>>>>>> Sincerely,
>>>>>>
>>>>>>
>>>>>> Gerard
>>>>>>
>>>>>>
>>>>>> p.s. And the answer to Curtis' question from the other day "Does
>>>>>> the input of the FADC-125 match the 0V to 0.5V output of the ASIC,
>>>>>> or is it something else?": For pulses of this shape, the input of
>>>>>> the ADC125 matches to an amplitude of 990mV, which is indeed
>>>>>> probably higher than intended (sorry). HOWEVER care is certainly
>>>>>> needed - for _wider_ pulses the ADC125 full scale will be _lower_
>>>>>> in amplitude (it is a shaper...). [And I presume the CDC can get
>>>>>> some pretty wide pulses when tracks pass at an angle.]
>>>>>>
>>>>>>
>>>>>> On 4/13/2011 2:54 PM, Fernando J. Barbosa wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> Hi Gerard,
>>>>>>>
>>>>>>>
>>>>>>> The preamp you have is set for a gain of 3.2 mV/fC and a
>>>>>>> dynamic range of 110 fC (@ 5% linearity), quite different from
>>>>>>> the CDC. This is the fifth row in the Table 2 of GlueX-doc-1364
>>>>>>> (the CDC is set as per the second row -
>>>>>>> 0.57 mV/fC,
>>>>>>> DR=380 fC).
>>>>>>>
>>>>>>>
>>>>>>> I attach the preamp configuration settings showing where the
>>>>>>> resistors are to be installed. To set your preamp to the CDC
>>>>>>> configuration, move the resistor to the left of the RC label to
>>>>>>> the pads on the right (5.1 Ohm resistor sets RC to logic
>>>>>>> 1) and move the resistor to the left of the HG label to the pads
>>>>>>> on the left (5.1 Ohm resistor sets HG to logic 0).
>>>>>>>
>>>>>>>
>>>>>>> The FDC cathode setting is the sixth row in Table 2 (2.6 mV/fC
>>>>>>> gain). Let me know if this works for you as this changes are easy
>>>>>>> to make with a soldering iron. If not, I will send you another
>>>>>>> preamp(s).
>>>>>>>
>>>>>>> There is GlueX-doc-1570 showing the dynamic range with the HVB
>>>>>>> and shows good linearity.
>>>>>>>
>>>>>>> Best regards,
>>>>>>> Fernando
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Gerard Visser wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> the preamp strapping picture (for current discussion)
>>>>>>>> http://npvm.ceem.indiana.edu/~gvisser/GlueX/straps.jpg
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>> --
>>>> Prof. Curtis A. Meyer Department of Physics
>>>> Phone: (412) 268-2745 Carnegie Mellon University
>>>> Fax: (412) 681-0648 Pittsburgh PA 15213-3890
>>>> cmeyer at ernest.phys.cmu.edu http://www.curtismeyer.com/
>>>>
>>>>
>>>>
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>>>>
>>>>
>>>>
>>>>
>>>
>
>
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