[Halld-tracking-hw] Tracking Meting Tomorrow

[Curtis A. Meyer]

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/