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Old 5th Aug 2017, 5:28 pm   #1
WaveyDipole
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Default Fuse for Fluke 8062A

I recently picked up a Fluke 8062A from eBay for the modest sum of £35. I thought I had done well. The meter was in good cosmetic condition, complete with Fluke soft case, probes and printed manual. The LCD is nice and clear. When I got it I checked it against my voltage reference and it was spot on - reading 10.002v against 10.0019 on another calibrated instrument. I then performed the fuse check described in section 2-4 of the manual which it failed. Upon investigation I found that one of the fuses had blown. The fuse in the battery compartment is a fast blow 2A/250V glass fuse and this was fine. The one that is blown is F2, which is 3A/600V which is a specialised fuse, measuring approximately 10mm in diameter and 34mm long. There is no part number provided. A reference to Busmann '448H' on the opposite gave me a clue and I have found similar fuses on eBay but the wrong rating. I am assuming that it should be possible to get brand new ones from somewhere like RS or Farnell but am not sure what to search for?

I have attached a photo showing the details.

Of next concern was whether there was any further damage. Since I had to open the case to access the fuse anyway, this afforded me an opportunity to visually inspect the interior. Fortunately, I could not see anything scorched or damaged. The wirewound resistor Z2 (tolerance matched) had a low resistance across it, however, since its exact value is not specified I cannot confirm that it is within spec. I clipped a jump lead across the fuse contacts and connected a few mA of current at a low voltage and got a sensible reading which would seem to indicate that otherwise the meter is OK and the fuse did its job of protecting it, so hopefully once the fuse is replaced it will be OK.
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Old 5th Aug 2017, 5:31 pm   #2
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Default Re: Fuse for Fluke 8062A

Ugh these are really expensive. Busmann BBS-3 are equivalent

http://uk.farnell.com/bussmann-by-ea...-3a/dp/1651750

As are littelfuse 3A BLS ones:

http://uk.farnell.com/littelfuse/0bl...-me-pd-mi-alte

They are HRC fuses with rupture tolerance of around 10,000 amps. These are the the last line of defence against transients and operator error.

RS sell these but only in packs of 10 for around £75!

Every damn Fluke I've bought off ebay has a blown one of them in it. I have paid more for the replacement HRC fuse than the meter on numerous occasions!
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Old 5th Aug 2017, 6:08 pm   #3
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Default Re: Fuse for Fluke 8062A

Galling when the price of a fuse is more than a complete (el cheapo) meter, but such protection is a reason why professional kit is the price it is.

No alternative to replace with one from a known, reliable, source though if you wish to be assured (IMHO vital) of the protection they give

If you choose not to replace with the correct fuse, please, please make this clear to anyone you you may pass the meter on to. Sensible people will know the limitations of a £5 meter, but may assume a good quality meter will protect them.
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Old 5th Aug 2017, 6:25 pm   #4
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Default Re: Fuse for Fluke 8062A

Very sensible advice.
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Old 5th Aug 2017, 6:27 pm   #5
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Default Re: Fuse for Fluke 8062A

Oh my word! £10 plus for a fuse! Just seen the RS listing and an eBay vendor selling them for £27 each! I fully intend to replace with the proper one (which is why I asked) which I will get from Farnell as I need to put in an order with them anyway, but it makes me wonder whether to send it back and ask for a refund. Still I did put in a cheeky offer and got it for substantially less than the original asking price, which I guess goes some way towards the cost of the fuse but frustrating nonetheless.
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Old 5th Aug 2017, 6:52 pm   #6
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Default Re: Fuse for Fluke 8062A

If you paid less than £50 including the price of the fuse then you got a good deal. The 8060 and 8062 are seriously good meters. I kind of expect this really. I've got an 8050 arriving sometime this weekend from an eBay seller that most likely has a blown up one in it
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Old 5th Aug 2017, 9:08 pm   #7
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Default Re: Fuse for Fluke 8062A

I just found that fuse for £7.50 at Raptor Supplies. However, postage is £10.60 and that is "Express" postage which takes 4-5 days.... Amazing what passes for "Express" postage these days

I guess if the deal on the meter is still reasonable then I will just get a fuse from Farnell. Both are 3A/600V and have a 10kv interrupt rating but the Littlefuse is half the cost of the Bussmann. I presume it is otherwise the same and does not compromise anything? I was thinking to get 2 x Littlefuse so as to have a spare.

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Old 5th Aug 2017, 9:17 pm   #8
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Default Re: Fuse for Fluke 8062A

As far as I know they are the same. I've seen them shipped with one or the other before. Both blown typically!

Edit: I've never blown one myself. The 2A fuses I pop regularly but I've never managed to pop the HRC one! Makes me wonder what people do to them.
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Old 6th Aug 2017, 2:23 pm   #9
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Default Re: Fuse for Fluke 8062A

Just as a confidence booster for your purchase, I just had an eBay 8050A delivered with a Littelfuse BLS-3 in it which hasn't been blown up!
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Old 6th Aug 2017, 4:15 pm   #10
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Default Re: Fuse for Fluke 8062A

Would a standard proper 13A plug fuse (3A of course) do if mains was the highest voltage expected to be measured? I would include radio HT in this too.
 
Old 6th Aug 2017, 4:50 pm   #11
Craig Sawyers
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Default Re: Fuse for Fluke 8062A

No! The whole point of the highly specified high rupture capacity fuse is that it can interrupt 10kA safely without forming a self-sustaining arc. Such an arc would spoil your day big time in a hand-held (or hand-holdable) DVM

And anyway a 3A plug fuse is the wrong physical size.

To the OP - there are also protection thermistors upstream from the fuses - they can also be blown, as can a fusible resistor in series.
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Old 6th Aug 2017, 5:35 pm   #12
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Default Re: Fuse for Fluke 8062A

Quote:
No!
I thought that 13A mains plug fuses are designed for a high enough rupturing current for general domestic mains use. Being sand filled and the like, proper ones anyway.
I have just looked at the spec. for a Bussmann 13A fuse, it is rated at 6000A rupture, I would have no hesitation in using one for my workshop as I only have single phase. Three phase (400+ volts and thicker wire) may well need 10kA though.

Quote:
And anyway a 3A plug fuse is the wrong physical size.
Only until you squeeze the holder.

Link to datsheet http://www.farnell.com/datasheets/16...571.1501096842

Last edited by Guest; 6th Aug 2017 at 5:36 pm. Reason: Added link
 
Old 6th Aug 2017, 5:49 pm   #13
Craig Sawyers
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Default Re: Fuse for Fluke 8062A

Well if you are comfortable doing that with a meter that is up to you. But my advice is to fit the correct fuse.

They are expensive, and they might just save your life, or prevent you losing a hand to arc burn.

Or even worse, you sell the meter and the person you sell it to does that.

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Old 6th Aug 2017, 6:04 pm   #14
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Default Re: Fuse for Fluke 8062A

Motivational video:

https://youtu.be/i9jpwGTy66g

Standard mains rated fuses sometimes arc over on transients.
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Old 6th Aug 2017, 6:41 pm   #15
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Default Re: Fuse for Fluke 8062A

Quote:
Standard mains rated fuses sometimes arc over on transients.
What fuse was (was!) in that meter on youtube? And what voltage/current capability was the feed. Given the right conditions you can blow anything up.

I do agree with Craig, and I would be happy using a mains (240V) fuse, if, however I was measuring 3 phase the 10kA fuse would be fitted and I would ask the question who blew the fuse, why and what can be done to stop that happening again.

I will leave with the question...
£35 bloomin' good meter used in domestic situations and a 6kA fuse.
or...
A new meter with rubbish fuses probably costing the same.
 
Old 6th Aug 2017, 7:58 pm   #16
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Default Re: Fuse for Fluke 8062A

Quote:
Makes me wonder what people do to them.
I can tell you. In automotive use, they leave the leads in the "Amps" position and then use the meter to test battery voltage. I have replaced *very* many of them while checking the calibration accuracy of the meter's Amps ranges.
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Old 6th Aug 2017, 10:42 pm   #17
Craig Sawyers
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Default Re: Fuse for Fluke 8062A

Another solid video taken during a training seminar at Fluke. Fast forward to 4m30s to watch a meter "with rubbish fuses" is left in ohms and a solid voltage is applied. Then imagine you are holding it at the time.

https://www.youtube.com/watch?v=OEoazQ1zuUM

Yup - use the correct fuse in a Fluke meter.
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Old 7th Aug 2017, 10:44 am   #18
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Default Re: Fuse for Fluke 8062A

The thing is, a 13A "plugtop" fuse is used in CAT II situations, where the maximum available energy has been limited by the MCBs or fuses upstream in the consumer unit. So it only has to deal with a relatively modest amount of energy relative to what you might see if you were poking the probes inside your fusebox.

Obviously the 8062 pre-dates the CAT ratings, but Fluke were aware of the issues long before the CAT rating scheme was introduced. Their first introduction to safe and rugged design goes right back to the 8000A, when they discovered the nasty business of high voltage transients on the mains: http://en-us.fluke.com/community/flu...to-safety.html

This article goes into the issues regarding fuses: http://en-us.fluke.com/community/flu...ur-tester.html

In short (groan ), the correct fuse is essential. On the positive side (groan ), you're a lot more careful when using a Fluke (other quality meters are apparently available ), because the price of the replacement fuses somewhat focuses your mind when using the meter. I've only every blown one HRC fuse (the 440mA one) - and because of the wallet-pain that induced, I don't want to make that mistake again!

RS have them for a fiver each, but you need to buy 5. It might be worth asking if anyone else would want to buy one from you - a "group buy" might work well? http://uk.rs-online.com/web/p/multimeter-fuses/3375284/

Oh, that video shows 750V into the Ohms function. A lot of those DT830 clones don't even have fuses - those that do use 20mm glass types. He does go on to talk about fuses a few minutes later. Luckily, you don't have to spend much more than DT830-money to get a reasonably rugged cheap meter that won't blow up with mains on the Ohms function, but meters with proper fuses cost a lot more again.
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Old 7th Aug 2017, 11:06 am   #19
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Default Re: Fuse for Fluke 8062A

Good idea. I'm up for a group buy if there is enough interest.
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Old 7th Aug 2017, 2:08 pm   #20
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Default Re: Fuse for Fluke 8062A

Quote:
Originally Posted by Craig Sawyers View Post
To the OP - there are also protection thermistors upstream from the fuses - they can also be blown, as can a fusible resistor in series.
Thanks. I am aware of that. After a visual inspection I did a test on all DC current ranges (using appropriate current limiting for each range) while bridging the fuse with a jump lead. I got a sensible reading on all of them and I could see no scorching or obvious sign of physical damage (cracks or disintegration) to any other protection components.

I did a little post-mortem of the fuse. The test mode on the meter had failed and it definitely read open. The contacts in the meter are completely corrosion free. I cut a slit in the end caps on both sides and eased one of them off gently and found that it came away without any resistance. Since the length of the wire attached was long enough to reach the solder at the other end, my first thought was that the solder joint had failed. However closer examination under the microscope clearly shows that the fuse wire has melted close to one of the ends. It also seems that the failure was not particularly violent, so perhaps the overload was not significant or maybe it occurred in a gradual fashion? It seems that the fuse did what it was designed to do and protected the meter.

Regarding the 'group buy', although I would not have minded, I don't see much advantage over Farnell who are quoting £4.91 ex VAT and I can order a qty of 1. I do also have to order some other things so hopefully postage will not be an issue either.

http://uk.farnell.com/littelfuse/0bl...-me-pd-mi-alte
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