DMM HRC Fuses

[orbiter]

Hi Fellas,

As you may have seen if you where following my Agilent/Fluke thread, I've got my self a new meter The thing is I'd like to know please if there are any special places you guys get your DMM fuses from? I've checked out Farnell's and RS however the fuses for my meter are £16+ a set. I don't mind paying that much for a spare set but would just like to know if you guys know of any places (preferably UK) that stock such fuses and are cheaper?

The fuses I'm after are.. 1x 440mA & 1x 11A (both 1000v)

Cheers guys

orb

[EEVblog]

Try:
http://www.maplin.co.uk/Module.aspx?ModuleNo=25433
http://www.rapidonline.com/Electrical-Power/Fuses-Circuit-Breakers/Industrial-Fuses/HRC-Ultra-rapid-fuses-for-digital-measuring-instruments/80232/kw/multimeter+fuse

Dave.

[orbiter]

Thanks Dave, Sorry I should have mentioned the fuse lenghts too (10x35 & 10x38mm) I believe the maplin ones are too short however the ones from Rapid look promising.

I guess just by the fact that they are HRC fuses means they're generally more expensive compared to ordinary fuses.

Thanks

orb

[Excavatoree]

...I guess just by the fact that they are HRC fuses means they're generally more expensive compared to ordinary fuses....

Very true.  Nothing like a 10 dollar (US) oops.

I'm sorry I can't help with UK sources.  Things are better in the US, I get them from Fluke directly, or the world famous auction site. (It might be worth a check - you may get lucky and find a UK seller)

[alm]

One important spec you should check for HRC fuses is the max. interrupting current, which is what HRC is all about. Should probably be something like 10kA for the 11A one. They should probably be fast fuses, but I'm not sure if they even make slow fuses in this format. Whatever you do, high-voltage HRC fuses are expensive, so I tend to try avoid blowing them up, by being conservative  (only connect it to the 400mA jack after I've checked it's significantly under 400mA) and obviously never connecting the current jacks to voltage sources like mains.

One option for low power circuits (eg. batteries) is connecting a normal glass fuse (faster/lower current than the HRC fuse) in series. In my opinion these are just fine for low power circuits (eg. batteries, or on the secondary side of a normal-size transformer), since plenty of equipment uses them on the primary side of a mains connection. Just keep them away from anything with lots of power or lots of voltage, and make sure they are isolated with no contacts exposed.

[Excavatoree]

^ Very good points.

I notice that the Fluke 25 and 27 (old type) do exactly that - it has a smaller, 630ma fuse in series with the 3A HRC. 

[NiHaoMike]

In my ECEN 214 class, the TAs spliced inline fuse holders into the multimeters because they had problems with students blowing expensive fuses by accidentally trying to measure voltage with the meter set for current.

[orbiter]

Good job I checked back on this thread, i've had no emails telling me there were responses even though I've got the option checked correctly

Anyway Thanks for the responses guys, I'll certainly heed the info regarding trying not to blow the fuses up in the first place I've got no information regarding the 'max interrupting current' you refer to alm. The meter handbook just states that the fuses are 440mA and 11A (35 & 38mm by 10mm.) I'm sure these will be fine but perhaps you could check the specs out for me please alm?...

http://uk.farnell.com/fluke/943121/fuse-1100v-440ma-fluke-943121/dp/546719

http://uk.farnell.com/bussmann/dmm-b-11a/fuse-test-equipment-11a/dp/1241956?in_merch=true&MER=i-9b10-00001422 

Regards

orb

[alm]

Strange that Agilent doesn't specify it. Do they specify to only use the correct Agilent part, or specific parts from other manufacturers like Bussmann?

You could check check the actual fuse, it's often printed on them. For example, on a 440mA fuse I have on hand (DM-44/100) I think it's the same as the one you link to), IR: 10KA in fine print. The data sheet from the second Farnell link actually mentions the IR, 20kA for the 11A fuse. The datasheet for the first link is useless, but if you go to the Fluke fuse selection guide (since they specify a Fluke part number), and select for example the 87-V (uses those same fuses I think), you'll see that Fluke p/n 943121 is 440mA/10kA/1000V.

Page 20 of the user/service manual (from the Agilent website) mentions that both fuses should be 30kA, so the fuses you link to are inferior to the original fuses. Although they are used by Fluke, I wouldn't trust the meter to meet its CAT III/IV specs after replacing a safety device with an inferior part (maybe their shunt has a lower impedance, or Fluke took other measures to limit the max. current). Page 103 specifies specific Agilent parts, although it wouldn't hurt to give the full specifications again. The specified Agilent parts will no doubt meet the specs, not sure if there are any standard Bussmann parts that meet it. The Agilent price for both fuses is $4.35, so it shouldn't be that expensive.

[orbiter]

Well spotted alm RE: 30kA, Thanks

Where did you find prices for the proper Agilent fuses? I'm lookng on the UK site but can't see anything

Regards

orb

[alm]

Agilent's Find-A-Part, and search for the Agilent p/n's from the manual. It's likely that a few fuses won't meet the minimum order quantity, at I'm not sure if they'll ship to the UK, but it at least gives an indication about you might expect (+distributor mark-up, plus the usual UK price gouging, plus shipping/VAT). You could ask Agilent UK (if there's such a thing) for UK distributors of the fuses, or ask the company that sold you the meter if they can sell you fuses.

[orbiter]

I actually searched the 'Find a Part' inputing my meters model numer but it doesn't recognise it, it just said 'No results were found that match your search criteria' As you suggested though using the actual part numbers sorted it out I'll give Agilent UK a call tomorrow and order a couple of each. I'm surprised at how cheap they are from Agilent direct. £3.47 each.

I actaully purchased the meter from Farnells as they are an Agilent authorized distributor, however neither Farnells or RS stock the fuses for this thing

Thanks again mate

orb