Need help picking an oscilliscope - Page 1
Forum section: electronics / beginners

author: JohnSays
author_rank: Newbie
timestamp: April 18, 2013, 05:00:13 pm
content: I need to measure some rather low frequencies. So, rather than needing super high end bandwidth I need low end. The trouble is that I only see the upper limits -- EG: 100MHz - mentioned. I need to measure from about .2 Hz up to about 10 KHz DC and AC. I want to buy a used scope because I don't have much money for my project and it will be used very infrequently. I am looking for a recommendation for a scope I might find on Ebay.com. (My last experience with a scope was high school 45 years ago where I built a Heathkit in electronics class.)

author: c4757p
author_rank: Super Contributor
timestamp: April 18, 2013, 05:05:42 pm
content: There's no lower frequency limit, they all go straight to DC. The only point I'd make is to get a digital scope so you can freeze the signal - you're not going to be looking at a 0.2 Hz signal in real time on a CRO.

author: JohnSays
author_rank: Newbie
timestamp: April 18, 2013, 05:45:14 pm
content: Thank you.

author: jpb
author_rank: Super Contributor
timestamp: April 18, 2013, 06:08:34 pm
content: If you're looking at very low frequency then you might want to consider using a sound card - I think there are various programs around to convert your sound card into a scope (I'm not an expert on this so you'll need to do some searching).Alternatives are data acquisition cards and USB scopes where you might get more bits than the 8 found on a scope.Other considerations are number of channels - if you want to go very low cost and only want to look at one signal at a time then you could use something like thePicoScope 2104. For 2 channels the Picoscope2204 is pretty cheap.Stand alone scopes are a bit more but the Rigol DS1052E is good value for money.

author: Smokey
author_rank: Super Contributor
timestamp: April 18, 2013, 06:29:08 pm
content: Do you plan on using a timebase so long that it rolls, or a trigger? One of the things to look out for when you are using a DSO with slow timebases (like in the ms range) with a trigger is that the samples/second drops like crazy and so does the screen update rate. So don't expect to get fast real time updating on the screen or be able to zoom in to the ns level on the captures. The newer the scope with high update rate and the deeper the memory the better.

author: JensAndree
author_rank: Contributor
timestamp: April 18, 2013, 07:10:05 pm
content: Being a total beginner in this area I can only recommend the DSO I just bought.https://www.eevblog.com/forum/beginners/cheapo-digital-scope-for-beginner-siglent-100mhz-2-channel/Low-cost but great value!

author: tinhead
author_rank: Super Contributor
timestamp: April 18, 2013, 07:31:32 pm
content: Quote from: JensAndree on April 18, 2013, 07:10:05 pma recommendation can be made based on test results between, not just because you bought something or you think something might have great value.And btw, beginner and recommendation? Sorry, but this didn't make any sense.

author: Jason
author_rank: Newbie
timestamp: April 19, 2013, 07:38:23 am
content: Can you tell us a little more about your project? It might help.A few questions:What are you logging? I assume it's some kind of sensor which outputs an analog voltage signal, but many industrial sensors may be current-based.What's the voltage range?How long will you be logging? Do you want a few seconds or a few days?Most sound cards are AC coupled and are useless below 10Hz, and DC measurements are impossible at any frequency. If you're only interested in frequency information it might work though.Try searching ebay for "USB Data Acquisition". That'll give you a bunch of prebuilt devices you can use.You can also do it with an Arduino - you can use any of the ADC pins to read a 0-1 or 0-VCC signal. A very simple bit of software (read analog, print value) might do what you need. The max sample rate is about 15KHz and you won't be able to print that speed continuously over serial, but it could easily record short bursts or give you frequency information a few times a second if that's what you need.Anyway, I hope some of this helps.