On Thu, 22 Apr 2021 05:03:16 +0000, bob prohaska wrote:

> Joe  wrote:
>> On Wed, 21 Apr 2021 20:22:27 +0200 Deloptes  wrote:
>>
>>> Theo wrote:
>>>
>>> > It is worth understanding what frequency range you're interested in.
>>> > Soundcards are typically 20Hz-20kHz.
>>> > SDR often has a limited bandwidth and doesn't go below ~30MHz.
>>>
>>> Ah, sorry I understood the opposite - I missed or misunderstood "I
>>> don't specifically need RF performance" as if OP was asking for RF
>>> explicitely :)
>>>
>>> I know only the PicoScope from the Automotive angle, but could be
>>> there are cheaper products that work with linux.
>>
>> Hantek is the name, or at least one of the names, many people rebadge
>> them. There is openhantek6022 which works for the cheapest scope.
>>
>> It's OK for DC and audio, which is all I need these days. If I have
>> frequencies a bit higher to deal with, I haul out my ancient Tek 465B,
>> which weighs about fifty times as much as the Hantek device.
>>
>>
> Hantek seems to be Windows-oriented, I have great respect for Tektronix,
> but analog scopes are no help with transients absent a Polaroid camera
> and a stable trigger pulse.
>
That depends on the scan rate: when I used mine to measure battery state
I ran the scan slowly enough the stretch the recovery signal across 30%
or so of the scan, so the time for the scan to cross the screen was
around 20 - 40 mS, and I fiddled with the scan trigger so that the
voltage drop as the solenoid pulled in triggered a single shot scan,

I think most 'scopes can be set to this triggering mode and low scan
speed, though its quite understandable that you'd not be familiar with
this way of using a scope if you've never needed to observe such
relatively slow events.

My scope's minimum scan speed is 200 mS/division, or 2 seconds to cross
the whole screen, so I'd have been running it at 10-15 ms/division to do
the battery condition check.

It helps to turn the brightness up enough that the whole scan is done
before the image fades.

FWIW the triggering device was a timer used to 'dethermalise', i.e. bring
down, a gliding model aircraft if it was still flying after a preset
time, typically three minutes after a switch on the towhook was last
operated as the model was launched from the top of its towline, so I set
that to 6 seconds (its smallest interval) during battery testing. The
battery being checked was a 4-5 cell NiCd used to drive the timer.

To see a trace, I simply flipped the towhook to start the timer and 6
seconds later the timer tripped and my scope drew a single trace across
the screen, which was easily visible long enough to see the shape of the
voltage drop and recovery and to measure the depth of the drop.


--
Martin    | martin at
Gregorie  | gregorie dot org

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