Re: [AH] buying an oscilloscope (was [AH] Visual patterns from analogue

From cheater00 .
Sent Sat, May 11th 2013, 23:30

YW. The thing with digital scopes is that unless you get one with
"digital phosphor" or "virtual phosphor", the display is going to be
really shitty, and you don't want a scope like that. Digital scopes
that have that cost a lot in general, rigol being the cheapest of the
pack. Seriously get an analog scope and don't worry about displaying
CVs, you can do that with your computer. A cheap analog scope is going
to be way cooler for creativity than a digital one, even a fairly
expensive one.

Cheers,
D.

On Sat, May 11, 2013 at 11:09 PM, bagofskin <bagofskin@gmail.com> wrote:
> Awesome advise. Thanks man!
>
> Scott
>
> On 2013-05-11, at 2:53 PM, "cheater00 ." <cheater00@gmail.com> wrote:
>
>> The "vector rescanning" technique is not possible on DSOs because they
>> alias waveforms. DSOs also suck for stuff like Lissajous patterns and
>> in general x-y display. But unless you get a bistable analog storage
>> oscilloscope like one of the Tektronix 7000 series bistable storage
>> scopes that start at around $400 used you have to use a digital scope
>> to see slow signals like CVs. Those are, however, well suited for
>> analysis via line-in - just get an analogue volt meter with recorder
>> output, select the right range, and take the output into your sound
>> card.
>>
>> When buying any scope, make sure it can do XY mode, that it's at least
>> dual trace, that it can subtract signals (A-B), and that it has
>> 1Megohm inputs, not 50 Ohm ones.
>>
>> Try to go for scopes where the CRT uses at least 20 kV acceleration voltage.
>>
>> When buying a scope from ebay, ask the seller if it has any burn-out
>> (don't buy one where there's something burnt into the phosphorus, like
>> on an old TV). Ask the seller to use the scope's callibrator (most
>> scopes have one, if not ask him to use an external one). The
>> callibrator is a square wave generator. Ask the seller to take a
>> picture of the scope displaying an image of the calibration signal on
>> each channel at once, such that the waveforms cover 80% of the
>> screen's height. Make sure the square waves aren't lopsided or curvy,
>> that there's no ripple, and that the traces aren't thick (a sign of
>> noise).
>>
>> When buying in person, make sure to plug it in and see if it works,
>> use the procedure above.
>>
>> Always ask if probes are included. It's a hassle to get extra probes.
>>
>> Once you get it, let it run for a couple days without shutting it off.
>> Make the trace very dim (just barely visible) so that it doesn't burn
>> anything in to the phosphorus, or even turn it down completely. See if
>> it still works afterwards. Don't give out any ratings until you've
>> done that.
>>
>> Learn what triggering is and check if it works. It's useful. A scope
>> with external trigger is useful for displaying synth waveforms and how
>> they react to filters etc, but only if you have a modular with a
>> counter.
>>
>> Cheers,
>> D.
>>
>> On Thu, May 9, 2013 at 1:54 PM, Thomas Strathmann <thomas@pdp7.org> wrote:
>>> On 08.05.13 21:31, Nicole Feeder wrote:
>>>> I bought an oscilloscope a few years ago. I looked around a lot for a
>>>> used one, but it was tricky for me to find something at the time. I
>>>> ended up settling on a small, new digital scope - Rigol DS1052E 50MHz.
>>>> I've been happy with it. It isn't quite as nice as some of the
>>>> Tektronix's scopes I have used, nor as sensitive and whatnot as some
>>>> analog scopes, but I was spoiled in the physics department for years.
>>>> For under $400 it is a nice, reasonably sized scope that fits on my
>>>> bench well and has good functionality.
>>>
>>> Seconded. I've got the 100MHz version which is basically the same
>>> machine. Compared to other (often fancier) digital scopes in the same
>>> price segment I'd say that the Rigol definitely feels sturdier and not
>>> as wobbly in day to day use. Although it should be noted that there are
>>> probably some DSOs that are quieter in operation. The fan in the Rigol
>>> is not the best possible one (a small, high-speed, low-cost thing). All
>>> in all I don't regret buying it and wouldn't go back to analog for most
>>> measuring tasks I do.
>>>
>>>        Thomas