'Megger' (Not) Insulation tester - good buy?

[Yorkie]

Some restorers use Meggers to test the leakage of capacitors - one such favoured model being the 'BM8 MK2' with an analogue meter, and I guess about early 1990s vintage. No doubt when they crop up they fetch silly money. Genuine new Meggers are beyond the pocket of amateur restorers, but I spotted this digital model from Hong Kong, which on the face of things, looks a reasonable buy and a capable bit of kit. Though it's referred to as a 'Megger' it isn't of course - I guess that in the same was that 'Hoover' has become a generic term for a vaccum cleaner, and 'Thermos' for a vaccum flask, 'Megger' has become generic for 'insulation tester' and occassionally, 'AVO' a generic term for any multimeter, analogue or digital, as in: 'have you checked it with an AVO?'.

Any thoughts on this bit of kit?

http://www.ebay.co.uk/itm/Digital-Insula...uipment_ET&hash=item4cf50e6dd6

[AlanBeckett]

David,
I don't see why it shouldn't be OK. However, I think it's a pity it doesn't have lower voltage ranges. I have a BM10 which has 50, 100, 250, 500 and 1,000v ranges so it's good for testing all sorts of Capacitors. In all honesty I would think that for (effectively) £35 you could get a BM10 or similar. Of course there would be the usual risks with a second hand unit.
I've also got a 'Wee Megger' and a couple of interesting Battery ones.
Alan

       

[Andrewausfa]

Looks OK David. Another manufacturer I see a lot of this sort of thing from is Robin. I don't know how far up the quality league table they are though not being a professional user. I spotted a variation the other week by Robin which has the same ranges as the Megger and yet another which seemed to have lower ranges, 25v to 250v from memory, I imagine for telephone linesmen.

I bought a BM8/2 after seeing an old post by Kat Manton on VRRR. Mine came from Stewarts of Reading so at £50 it may have been a bit premium priced though guaranteed, with leather case and a nice set of Fluke shrouded leads. I've noticed prices seem to be higher since the post about testing capacitors with a Megger appearred on VRRR, it's always the way!

Andrew

[Yorkie]

Hi Guys,

Thanks for reading, and for your comments.

As to the BM8/2, there doesn't seem to be any around at the moment, but I think you've hit the nail on the head as to why Andrew!

[Alistair D]

The one problem I know of is that the meter movement is a taut band type rather than needles and cups. They are a bit delicate and really don not like being dropped. I now use mine with an external meter and read the leakage current.

I have the manuals if you want a read.

Al

[Andrewausfa]

I thought I'd add a couple of photos of the BM8 'in action' as it were, if anyone hasn't seen one.

Testing a 1940's GEC wax capacitor at 500v and then a 60s' Plessey Duomold at 500v..which did rather well I thought.

Andrew

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[Yorkie]

Way to go Andrew!

Thanks for the pics.

[Radio Fixer]

Look out for Levell TM14 Insulation tester at swap meets... Bought mine for a few pound and apart from new batteries and a bit of cal its been fine and a really useful piece of kit.

Have the manual of you find one

Gary

[Andy M0FYA]

Coincidentally when David posted the question about the VC60B+ insulation tester, I had just decided to order one. (As it happens, not from the supplier in the link, but another ebay shop who ship from within the UK rather than direct from China).

It arrived this morning and I have had a play with it. Although its operation is fairly obvious, my only criticism is that the instruction book is only in Chinese! I have emailed the seller to ask if an English version is available, just in case I have missed anything obvious.

I have only tried it out on a few 0.1 and 0.5 uF NOS capacitors on the 250v range so far (I agree it would be more versatile if it also had lower test voltages), and have got readings of between 7 and 20 Mohms. What would be considered to be a 'fail' reading?
To check the accuracy, I measured 15 Mohm and a 200 Mohm hi-stab resistors and the results were spot on.

It looks like it should prove useful!

Andy

[Radio Fixer]

Well I wouldnt be using either of those caps... just chuck 'em away and restuff with modern and cheap poly. Those are way into the G Ohm.

7M would be too low for AVC lines and the 20M about useable. Of course they probably leak less at AVC line voltage but you cant test them at say 25V !!

Anyway why use them ?

Gary