Review - UNI-T UT81B Scope / Meter - Page 2

REDBEEMER43 · 13th June 2011, 08:59 AM

No, you're not being picky and yes, you're right it is a LBC (glass) fuse, but there's no reason you can't fit a HBC one; though I must admit I'm never likely to use this instrument on mains supplies; it's more for bench use on audio systems etc. where the fault level is nowhere near that of a domestic, or industrial, supply system. For the latter one is definitely safer using pukka (certified) kit like my trusty Fluke DMM which is, after all, specifically designed to be safe on such systems having a fuse with a rupturing capacity in the kA range.

With that reservation and the application of a modicum of common sense in its use I still think it's good value and a worthy addition to my test kit - it's still a pity about the lack of a probe compensation set-up signal though!

As an after-thought, have you looked at the "dpscope"? - not a stand-alone 'scope as it needs to be tethered to a P.C. (Windows, NOT a Mac, sadly!) but great value twin-channel, pretty versatile AND it has a probe compensation output! - PDAMusician's PocketPC Music Softwaredpscope/

Hope the comments are useful; let me know what you get and what you think.

Dave.

TheLaw117 · 13th June 2011, 10:37 PM

Quote:

Originally Posted by REDBEEMER43

No, you're not being picky and yes, you're right it is a LBC (glass) fuse, but there's no reason you can't fit a HBC one; though I must admit I'm never likely to use this instrument on mains supplies; it's more for bench use on audio systems etc. where the fault level is nowhere near that of a domestic, or industrial, supply system. For the latter one is definitely safer using pukka (certified) kit like my trusty Fluke DMM which is, after all, specifically designed to be safe on such systems having a fuse with a rupturing capacity in the kA range.

With that reservation and the application of a modicum of common sense in its use I still think it's good value and a worthy addition to my test kit - it's still a pity about the lack of a probe compensation set-up signal though!

As an after-thought, have you looked at the "dpscope"? - not a stand-alone 'scope as it needs to be tethered to a P.C. (Windows, NOT a Mac, sadly!) but great value twin-channel, pretty versatile AND it has a probe compensation output! - PDAMusician's PocketPC Music Softwaredpscope/

Hope the comments are useful; let me know what you get and what you think.

Dave.

No I've never heard of it but I just looked it up, and it seems decent to say the least.

Component selection looks nice. All genuine Microchip silicon, unlike the nice unmarked ones on the Uni-T . A Wima cap in there. Panasonic electrolytic and plenty of MLCCs/Tantalums.

Pretty cheap as well. I'm considering buying just the PCB and ICs for $20. Other components hopefully wouldn't cost any more than $20-30USD.

Looks nice, really....How about a protection circuit on this one? Or is it different with PC based ones. I don't really see any MOVs, PTCs, discharge tubes, current sense etc. I'm going to take a half a bet that those two cylindrical things close to the inputs are fuses. Not sure what else they've got.

But I'll consider it. Maybe I'll throw my Pentium 3 down by my bench.

womai · 14th June 2011, 05:21 AM

Hi,

since I am the designer of the DPScope I thought I should add some answers:

As far as input protection is concerned, these posts hopefully answer your questions:
dpscope.freeforums.org • View topic - Can I damage my computer with large voltages at the scope?
and
dpscope.freeforums.org • View topic - How can I measure voltages larger than 20V?

The "two cylindrical things" are actually trimmer capacitors and are used to compensate the scope inputs so the response stays flat up to the full required bandwidth; without capacitive compensation the input stage would have a measly 60 kHz bandwidth...

I have a pretty detailed explanation of the hardware design (including the input stage) on my website:
DPScope - A Low-Cost PC-Based Oscilloscope

Feel free to ask more questions if anything is still unclear! I'm doing this as a hobby and I am always glad if people get some use out of what I design.

Regards,

Wolfgang

REDBEEMER43 · 14th June 2011, 08:29 AM

Re the dpscope - there, you've got the answer straight from the horse's mouth (no offence, Wolfgang!) and there's not much I can add except that if you go DIY you don't get the SMD setup that is in the ready-built one: I debated whether or not to go for DIY but am perfectly happy with the price of the ready-built unit, it is very well made (better, I think, than I could do) and for the saving you'd make, not worth the bother of DIY'ing.

Dave.

TheLaw117 · 14th June 2011, 10:43 PM

If I have the opportunity to DIY, I do it....even if its a few dollars more.

Anyway, I didn't know the max voltage was 20V. That's okay for most things, but....honestly, I'd like something more in the range of 50V.

But I can measure up to 200V in 1:1 mode?

I'd probably only use my o-scope for things with lesser voltage anyway, and the price is very good, so it's hard to say.

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13th June 2011, 08:59 AM	#11
REDBEEMER43 diyAudio Member Join Date: May 2010 Location: North-eastern England	No, you're not being picky and yes, you're right it is a LBC (glass) fuse, but there's no reason you can't fit a HBC one; though I must admit I'm never likely to use this instrument on mains supplies; it's more for bench use on audio systems etc. where the fault level is nowhere near that of a domestic, or industrial, supply system. For the latter one is definitely safer using pukka (certified) kit like my trusty Fluke DMM which is, after all, specifically designed to be safe on such systems having a fuse with a rupturing capacity in the kA range. With that reservation and the application of a modicum of common sense in its use I still think it's good value and a worthy addition to my test kit - it's still a pity about the lack of a probe compensation set-up signal though! As an after-thought, have you looked at the "dpscope"? - not a stand-alone 'scope as it needs to be tethered to a P.C. (Windows, NOT a Mac, sadly!) but great value twin-channel, pretty versatile AND it has a probe compensation output! - PDAMusician's PocketPC Music Softwaredpscope/ Hope the comments are useful; let me know what you get and what you think. Dave.

14th June 2011, 05:21 AM	#13
womai diyAudio Member Join Date: Feb 2010	Hi, since I am the designer of the DPScope I thought I should add some answers: As far as input protection is concerned, these posts hopefully answer your questions: dpscope.freeforums.org • View topic - Can I damage my computer with large voltages at the scope? and dpscope.freeforums.org • View topic - How can I measure voltages larger than 20V? The "two cylindrical things" are actually trimmer capacitors and are used to compensate the scope inputs so the response stays flat up to the full required bandwidth; without capacitive compensation the input stage would have a measly 60 kHz bandwidth... I have a pretty detailed explanation of the hardware design (including the input stage) on my website: DPScope - A Low-Cost PC-Based Oscilloscope Feel free to ask more questions if anything is still unclear! I'm doing this as a hobby and I am always glad if people get some use out of what I design. Regards, Wolfgang

14th June 2011, 08:29 AM	#14
REDBEEMER43 diyAudio Member Join Date: May 2010 Location: North-eastern England	Re the dpscope - there, you've got the answer straight from the horse's mouth (no offence, Wolfgang!) and there's not much I can add except that if you go DIY you don't get the SMD setup that is in the ready-built one: I debated whether or not to go for DIY but am perfectly happy with the price of the ready-built unit, it is very well made (better, I think, than I could do) and for the saving you'd make, not worth the bother of DIY'ing. Dave.

14th June 2011, 10:43 PM	#15
TheLaw117 diyAudio Member Join Date: Sep 2010	If I have the opportunity to DIY, I do it....even if its a few dollars more. Anyway, I didn't know the max voltage was 20V. That's okay for most things, but....honestly, I'd like something more in the range of 50V. But I can measure up to 200V in 1:1 mode? I'd probably only use my o-scope for things with lesser voltage anyway, and the price is very good, so it's hard to say.

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