New oscilloscope faulty? - Page 1
Forum section: electronics / testgear

author: naujoks
author_rank: Regular Contributor
timestamp: September 08, 2020, 06:07:19 am
content: Newbie here, bought a cheap-ish (220€) oscilloscope off Amazon (2 channel, 110MHz).It's the first time I bought/used one and I was trying to test it, but either I'm doing something wrong or it's faulty.It's got a 5V test signal on the front. When I connect the probe to the +5V point, I get a reading on the screen, but I haven't even connected it to ground yet! When I do connect ground, the signal goes flat.I tried a 1.5V battery, again when touching the + pole with the tip of the probe, I'm getting a reading of sorts, but when touch the - with the ground part of the probe, the signal vanishes.That doesn't make any sense to me. Could you tell me if I'm doing something wrong, or if the scope might be faulty?

author: tkamiya
author_rank: Super Contributor
timestamp: September 08, 2020, 06:21:35 am
content: On front of the scope, there is a test probe hook. Typically, it puts out square wave. Ground is not necessary as that circuit and measuring circuit shares common ground inside.If you connect a battery, you might see a quick peak and go flat. That's because you are likely set to AC coupling. It will see the change from 0 to 1.5V, then it stays there and no change; thus, it goes flat. You need to couple DC. There should be a selection for your channel setup.It would be the best if you can find someone local who can quickly show you how to use it. It's not hard. It's just hard to explain using text only like this.By the way, what model did you buy?

author: coromonadalix
author_rank: Super Contributor
timestamp: September 08, 2020, 09:13:47 am
content: Same as tkamiya wroteAnd you have some tutorials on youtube who could help if you are new to these pieces of equipement

author: naujoks
author_rank: Regular Contributor
timestamp: September 08, 2020, 09:33:42 am
content: Thank you, it was the DC coupling.The model I got is called Hanmatek DOS1102. It was on special offer for 166€, normal price is 60€ more.I'd like to learn about repairing arcade game PCBs and for that the oscilloscope should come in handy.

author: tkamiya
author_rank: Super Contributor
timestamp: September 08, 2020, 02:01:50 pm
content: Nice.Enjoy your new scope. Just be sure you don't try to measure non-isolated mains voltage without understanding all of the consequences. You can easily blow your input via ground side.

author: rf-loop
author_rank: Super Contributor
timestamp: September 08, 2020, 03:28:59 pm
content: Quote from: naujoks on September 08, 2020, 09:33:42 amLooks like, or is better say - it is, rebranded Owon DS2102 or something like it.https://detail.tmall.com/item.htm?spm=a1z10.5-b-s.w4011-18859920914.81.604c20bfXVVKwS&id=578505002030&rn=cfdc4d62d8a5d602d3079120aee3e481&abbucket=14&skuId=3893975312408

author: naujoks
author_rank: Regular Contributor
timestamp: September 08, 2020, 04:19:49 pm
content: Yes, that looks like it.I hope that it's suited for the purpose I bought it for, 8bit 80s computing.

author: tkamiya
author_rank: Super Contributor
timestamp: September 09, 2020, 03:56:42 am
content: I've been in electronics for long time. One thing I've learned along the way that helps me a lot is, always doubt my own work first. Maybe it's just me but I make so many dumb mistakes that whenever I want to attribute what I'm seeing as circuit or test equipment's fault, it usually ends up problem being ME, the operator. Still, it's rare something I purchased is faulty. Not saying it doesn't happen. But chances are, it is I who is not doing something right.