Testing sine wave output from portable power stations (with inverters)? - Page 1
Forum section: electronics / beginners

author: artv
author_rank: Contributor
timestamp: May 28, 2021, 01:13:34 pm
content: HiI've bought a Mustool MT8208 oscilloscope multimeter. I'm testing portable power stations with AC outlets to confirm they offer pure sine wave output from their built in inverter (some cheaper models are a modified square wave and not suitable for more sensitive electronics.)I'm trying to work out the easiest/safest way to to do this. I was thinking of wiring test leads from the multimeter to a UK plug - red to live, blue to neutral - they'll be no ground. The units are standalone - basically batteries, with built in inverters.Would this be ok - or is there a better option? Or is there another simple tool I could use. Would have £50-100 to spend - all I really need it to do is this one task.Any advice appreciated!Thanks.(This is the meter I've ordered:https://www.banggood.com/MUSTOOL-MT8208-Intelligent-Graphical-Digital-Oscilloscope-Multimeter-2-in-1-With-2_4-Inches-Color-Screen-1MHz-Bandwidth-2_5Msps-Sampling-Rate-for-DIY-and-Electronic-Test-Upgraded-from-MT8206-p-1707883.html?cur_warehouse=CN)

author: penfold
author_rank: Frequent Contributor
timestamp: May 28, 2021, 01:31:57 pm
content: As long as you use appropriately insulated banana plugs and a suitably insulated cable, it should be okay. I had a Fluke test lead of a similar arrangement, though it was double insulated (PVC mains flex type) over most of its length and only split into singles over the last 10cm or so.Compared with silicone test leads, I think I would preferentially use some mains flex cord (with heat-shrink serving as second insulation of the inner cores where the outer jacket is removed) because it offers better strain relief at the plug end... and accidents happen.With that meter, please check whether it has a suitable over-voltage category rating before considering connecting to "real" mains voltages though.

author: artv
author_rank: Contributor
timestamp: May 28, 2021, 01:56:44 pm
content: Many thanks.The manual (http://myosuploads3.banggood.com/products/20200714/20200714042733SKUF67117.pdf) states:...◆Overload protection 500mA/10A double protective tube, dual protection of the instrument...Function: A AC/ DC 10A，COM 10A DC/AC effective value，within 30 seconds，15-minute coolinginterval . 250V/10A fuse type protective tube...This digital oscilloscope multi-meter is designed in conformity with safety specifications of IEC1010-1. Secondcategory of overvoltage measurement: CAT III - 1000V; pollution protection level: Level 1.Do you think that looks ok for uk mains voltage 230V?Thanks.

author: nfmax
author_rank: Super Contributor
timestamp: May 28, 2021, 02:00:30 pm
content: I made a test adapter out of a scrap remote controlled socket:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3061408/#msg3061408

author: penfold
author_rank: Frequent Contributor
timestamp: May 28, 2021, 03:04:35 pm
content: Quote from: artv on May 28, 2021, 01:56:44 pmYeah, on paper that looks okay. After seeing some of the multimeter surge testing videos, I'd be wary of hand holding a cheap meter or putting my face anywhere near it when connected to mains. I avoid hand-holding even more reputable meters during mains testing anyway, maybe just force of habit.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 29, 2021, 12:00:25 pm
content: Make sure to put a nominal load on before starting up and testing-Do not mess about with battery connections at these high currents.Its a CAT II meter. Check it has a real HRC fuse inside.Seehttps://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjKm9Wr6-7wAhXeA2MBHceQB94QFjAAegQIBBAD&url=https%3A%2F%2Fcontent.fluke.com%2Fpromotions%2Fpromo-dmm%2F0518-dmm-campaign%2Fdmm%2Ffluke_dmm-chfr%2Ffiles%2Fsafetyguidelines.pdf&usg=AOvVaw3lnXyQ8ApU5lSpR77_Wqrp

author: artv
author_rank: Contributor
timestamp: May 31, 2021, 01:17:00 pm
content: Thanks - forgot to enable notifications on this post.@nfmax - looks good.@penfold - thanks. I would plug in and then turn on the supply from a distance just in case!@Terry Bites - thanks. How would I do that if I'm plugging in this multimeter? I'm not really sure how to confirm it has HRC fuses? And when you say it's a CAT II meter - are you saying that's ok - it's listed as a CAT III tester?

author: Gregg
author_rank: Super Contributor
timestamp: May 31, 2021, 09:35:34 pm
content: Please open your Mustool MT8208 and post some pictures of the insides. It looks like it may be a reasonable meter for quick look at many things like inverters and wall-warts without setting up a lot of test equipment.