Date: Wed Oct 29 23:50:30 2008

Author: Bernard Cleyet

Subject: Re: oscilloscope renewal

Post:

--------------------------
"However, in the Normal mode, the only choice is infinite! Yep -
no matter what, the scope displays the previous pulse until superseded."

----------------------------------------------------------
What is normal mode?

I thought to set the Tek. in a persistence desired (not infinite)
set it's discriminator very sensitive and use the external
discriminator.

bc's problem may be not knowing "normal mode".


On 2008, Oct 29, , at 11:23, J. Terrence Klopcic wrote:

> No no. The problem is not the discriminator. The problem is that
> the scope retains the previous trace so you cannot use the presence
> of a trace to detect/select pulses.
>
>
> J. Terrence Klopcic, PhD
> Director of Laboratories
> Departments of Physics and Mathematics
> Kenyon College
>
>
>
> Bernard Cleyet wrote:
>>
>> A discriminator is easily constructed, especially for multi
>> microsecond pulse widths -- look in Elmore and Sands.
>>
>> bc vacuum tube man.
>>
>>
>> On 2008, Oct 29, , at 08:45, J. Terrence Klopcic wrote:
>>
>>> On the subject of oscilloscopes.
>>>
>>> We have made a disappointing discovery in connection with our new
>>> Tektronix digital oscilloscopes.
>>>
>>> One of the handy uses of a scope is to find random signals in a
>>> noisy background. The way one can do this is to set the trigger
>>> to the "Normal" mode. (In this mode, the scope does not sweep
>>> until a pulse exceeds the trigger level.) One then starts with a
>>> low trigger level - which displays the noise - and slowly
>>> increases the trigger level until the noise disappears. At that
>>> point, the sweeps are all initiated by pulses that exceed the
>>> noise level - and one can judge the frequency of such pulses by
>>> the persistence of the traces which overlap at the beginning of
>>> the trace.
>>>
>>> Not so with the Tektronix TDS 2022. That scope has a Persistence
>>> Setting (0, 1, 2, 5, or infinite seconds) for individual traces -
>>> a very handy thing if one wants to study individual traces.
>>> However, in the Normal mode, the only choice is infinite! Yep -
>>> no matter what, the scope displays the previous pulse until
>>> superseded. When contacted, Tektronix replied that such behavior
>>> is "Industry standard". Yuk! Why offer a Persistence setting
>>> and then automatically over-ride it? It is a disappointment.
>>>
>>> Anyone else bothered by this behavior and found a work-around?
>>>
>>> Terry
>>>
>>> J. Terrence Klopcic, PhD
>>> Director of Laboratories
>>> Departments of Physics and Mathematics
>>> Kenyon College
>>
>> cut


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