Noise Levels between Scope Models 3243 vs 4425

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Re: Noise Levels between Scope Models 3243 vs 4425

Postby FioranoCars » Fri Jun 02, 2017 5:49 pm

Hi Again
Yes, all quite valid thoughts and yes, all and more tried over the last 12 years of owning Pico kit!

USB cable is USB3 Pico brand for the 4 series but others inc Pico USB2 and third party leads, only USB2 with the 3 series scope (does not have usb3 capability) but both scopes tried with a variety of cables, including length and thickness/quality. No difference to noise levels.

Desktop and Laptop, both battery and mains powered (and yes some laptop power supplies, aftermarket especially, can cause lots of noise, so that should be your first point of call when evaluating noise issues). Battery only operation tends to always result in some reduction in noise, but often the noise is not an issue from good supplies, but good to know it can be reduced.

We did monitor the scopes current draw not that long ago, along with some Diagnostic interfaces, and neither/none gave cause for concern (don't remember why we did, but we did it!), well below the power a mobile phone drags out the same port.

In fact, I think it was when considering powering pressure transducers from the USB port of a laptop, but decided based on cable lengths and cable routing that a simple DC-DC buck transformer gave a more satisfactory solution for less cost and much more stability/versitility (effectively 8-36v source voltage, so 12 or 24v vehicles could be used with ease).

I'd be interested to hear what your tests have shown in terms of increased current draw based on what sampling rates and the actual scope used and cable USB2 verse USB3? Please give me some examples and your methods ...

I think you'll find all of these issues were discussed or raised in this or another earlier thread, but might be useful for someone else to have in one place.

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Re: Noise Levels between Scope Models 3243 vs 4425

Postby e2e4 » Fri Jun 02, 2017 7:40 pm

I don't own any Pico oscilloscope, I'm just considering buying one 4425 or some other automotive digital oscilloscope. A 2235 Tektronix, analogue, 100MHz oscilloscope is what I own. You should find a laboratory pulse generator so that you can connect your oscilloscope to it, just to check if there is some strong ringing on the pulses. The ringing shouldn't be there of course. If you see strong ringing on the pulse generator's square wave signal your oscilloscope is at fault.
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