[SI-LIST] Re: Jitter measurement floor on different high bandwidth oscilloscopes
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Heyfitch <heyfitch@xxxxxxxx>
- Date: Thu, 10 Jun 2010 09:23:42 -0700
This is why before coughing over the price of a condo for a scope and
probes you really need to evaluate instruments like these on your own
turf with a test set-up you fully understand. The investment in probes
alone is going to have a strong influence on purchases for many years.
As the Templar Knight said: "Choose wisely."
Steve.
Heyfitch wrote:
> Agilent's app note 1491 (5989-0553EN.pdf) illustrates the points Steve made
> below. (Never mind that it is written by Agilent and naturally shows that
> Agilent's solution is "far superior" to Tektronix' one.)
> - Vadim
>
>
> On Wed, Jun 9, 2010 at 11:49 PM, steve weir <weirsi@xxxxxxxxxx> wrote:
>
>
>> Be wary of specifications and marketing hype and FUD. Modern scopes are
>> very dependent on the signal processing: analog and especially digital.
>> Where one vendor claims advantage in slew rate another claims advantage
>> in noise floor. Overactive DSP algorithms have been seen in various
>> scopes that create waveform artifacts that are not real. I've gone
>> through considerable pain with customers whose scopes were lying to
>> them, where we had to set-up experiments with better behaved instruments
>> in order to get them to see the truth. You want to know that if you
>> follow good measurement practice that what your scope tells you is
>> faithful, and not a DSP induced fantasy.
>>
>> Claims are all find and good, but for the kind of money that you are
>> spending, you owe it to yourself to have each vendor come in with their
>> scopes and put them through paces with a clock / pulse generator that
>> you supply in probing configurations that you set-up as representative
>> of the type of work you expect to do.
>>
>> The other thing that you should take into careful account is that modern
>> scopes represent an investment in probes that is often similar to the
>> price of the scope itself. It is just as important to evaluate the
>> probes: How they perform, do they meet your physical access needs, how
>> much do replacement supplies cost for things like solder ins cost, what
>> probes are you already invested as anything else about the scope.
>>
>> Steve.
>> prasad wrote:
>>
>>> Hi every one....
>>>
>>> i am evaluating high bandwidth oscilloscopes (12GHz) from different
>>> vendors. I was looking the data sheets of them. One of the
>>> them(DSO91204A) has very good noise floor compared to others. Though
>>> its a good thing for me but when it comes to the jitter measurements ,
>>> the lowest jitter that can be measured on that is dependatnt on the
>>> slew rate of the signal ,which is actually true(since the voltage
>>> noise will have a second order effect on the timing of the signal).
>>> But when i looked at one more vendor (SDA13Zi) the noise floor is poor
>>> compared to other. In which case the lowest jitter that can be
>>> measured (jitter measurement floor)should be higher than earlier. But
>>> if you look at the datasheet, they have specified a fixed value for
>>> this which is very less .
>>> My question is , if the noise floor is high in the second box how
>>> would the jitter measurement floor be less?
>>> second one is , since the timing noise(jitter) is dependatnt on slew
>>> rate, how a fixed value is given in datasheet?
>>>
>>>
>>> please help me understand. Am i missing some other factor here?
>>> Welcome all your suggestions and ideas...
>>>
>>>
>>> thanks in advance...
>>> prasad
>>>
>>> h
>>>
>>> On 09/06/2010, colin_warwick@xxxxxxxxxxx <colin_warwick@xxxxxxxxxxx>
>>>
>> wrote:
>>
>>>> (Note: I sent this info to Hermann off-list but he suggested it might be
>>>>
>> of
>>
>>>> general interest. Send flames to me, not Hermann, if it isn't.)
>>>>
>>>> In ADS the implementation is:
>>>>
>>>>
>>>> "Fast" corner
>>>> (a) the max values are selected for all the I-V data (Pullup, Pulldown,
>>>> Power Clamp a Ground Clamp) and for the waveform data (Ramp, Rising
>>>>
>> Waveform
>>
>>>> and Falling Waveform), and
>>>> (b) the min values are selected for all R, L, C, delay and TT data.
>>>>
>>>>
>>>> "Slow" corner is the reverse obviously
>>>> (a) the min values are selected for all the I-V data (Pullup, Pulldown,
>>>> Power Clamp a Ground Clamp) and for the waveform data (Ramp, Rising
>>>>
>> Waveform
>>
>>>> and Falling Waveform), and
>>>> (b) the max values are selected for all R, L, C, delay and TT data.
>>>>
>>>>
>>>>
>>>> -- Colin
>>>>
>>>> -----Original Message-----
>>>> .
>>>> .
>>>> .
>>>>
>>>> Any feedback from the tool vendors how they implemented this selection ?
>>>>
>>>> Thanks and Regards
>>>>
>>>> Hermann
>>>>
>>>> EKH - EyeKnowHow
>>>> Hermann Ruckerbauer
>>>> www.EyeKnowHow.de
>>>> Hermann.Ruckerbauer@xxxxxxxxxxxxx
>>>> Veilchenstrasse 1
>>>> 94554 Moos
>>>> Tel.: +49 (0)9938 / 902 083
>>>> Mobile: +49 (0)176 / 787 787 77
>>>> Fax: +49 (0)3212 / 121 9008
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>>>>
>>>>
>>>>
>>>
>> --
>> Steve Weir
>> IPBLOX, LLC
>> 150 N. Center St. #211
>> Reno, NV 89501
>> www.ipblox.com
>>
>> (775) 299-4236 Business
>> (866) 675-4630 Toll-free
>> (707) 780-1951 Fax
>>
>>
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>
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--
Steve Weir
IPBLOX, LLC
150 N. Center St. #211
Reno, NV 89501
www.ipblox.com
(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax
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