Oscilloscope/frequency measurement/multimeter suggestions

Yo!

I’m looking for an oscilloscope for basic tasks, like adjusting turntable pitch or x0xb0x tuning. I think best would be an analog second hand thingie from ebay. Any suggestions? I have no experience with oscilloscopes so far.

Cheers!

Oh, if possible, I don’t want to spend more than 100 Euro. Is this realistic?

Get one with a square display, anything with a circular display will be ancient.

Being an analogue device they need calibration and therefore you won’t be able to rely on its readout unless it has been calibrated.

They vary in their maximum frequency display, 20Mhz being the low end but still perfectly fine for visualising anything in the audio frequency range (20-20Khz normally).

Hmm do I need anothere oscilloscope for calibration? :smiley:
I guess digital ones are not in the <100 Euro price range?

You can get small digital handhelds cheap, although I’ve no idea if they are any good.

eg. ARM DSO201

Even without calibration you can probably compare two turntables (one good, one bad) using the two inputs of the scope and adjust the bad one to match the good one.

It’s realistic to expect a basic 20 MHz dual channel analog scope from the 80s to be sold at ~ 100€. I often see those, and from reputed brands (Hameg, Metrix, Tek). A bit more (say 140€) and you’re in the range of people selling their Rigol/Atten.

However, while there are many uses to a 20 MHz analog scope for design&troubleshooting, frequency tuning would not be the best use. You might try instead some of the pocket meters with a built-in frequency counter. A frequency counter is a simple circuit that doesn’t need fancy parts to work well (it’s really just a quartz and basic stuff around it) - so for < 1 MHz, low-end meters won’t be significantly different from expensive equipment. It will be much more accurate than reading frequencies out of a scope grid (unless you have other approaches to tuning, ie with lissajoux patterns - but this requires a refrence frequency source - which is another problem…).

calibration of a technics turntable is also possible with the point markings on the turntable in front of the red LED. But doing it with an oscilloscope is much easier because you don’t have to remove the turntable and put it on again constantly. I think a VERY basic oscilloscope should be enough for this…

So pichenettes, you would suggest getting a cheap digital scope new instead of the used analog one, like the one 6581punk linked to?

or maybe just get a <5 euro usb soundcard and use a software oscilloscope like this: http://xoscope.sourceforge.net/ ?

Oh wait, for the turntable tuning you have to set a frequency of 262,08 kHz, so that won’t do…

i have an uncalibrated hameg from the bay for 80€ which works perfectly fine for troubleshooting.

@fcd72: Yes, something like that was my first thought. What is the calibration really necessary for?

An oscilloscope is like a meter, has scales for the vertical and horizontal. Vertical being volts and the horizontal being the time period.

If your scope is not calibrated then if it reads 5V it could be 10, could be 1v. Same with the frequency, you’ll see a waveform that seems to be at 20Khz but could be 10 in reality.

nope.aybe it shows 5v if the real value is 4.95v so its accurate enough for diy trobleshooting, but probably not for rocketscience nuclear devices…

btw: my hameg has a built in voltage/frequency reference for calibration…

OK, so I guess for the turntable tuning it should be calibrated.

262,08 kHz (+/- 0,05 kHz) is suggested there…

if you are for more than 1% accuracy yes

I was exaggerating :slight_smile: it will probably be off a small amount. But if you’re buying something used on ebay it can be an unknown quantity, especially if it has been bashed about in transit.

Hmm, so maybe a cheap digital one is my best bet. Any brand/product suggestions there?

Your problem is measuring frequency to a very specific number, why do you insist on using a scope for that (and how would you have done it?). The tool for a frequency measurement job is a called a frequency counter, and as I have said it comes bundled with some very cheap multimeters.

262kHz is too high for soundcard based stuff, and the cheap digital scopes have a 1 MHz bandwidth/sample rate so you won’t be able to make any precise measurement.