UT71C fuses, is this an oversight on the manual/board or is this correct? (250v) - Page 1
Forum section: electronics / testgear

author: XOIIO
author_rank: Super Contributor
timestamp: May 09, 2014, 12:43:28 pm
content: Something I am just wondering about, it has both a .5 amp fuse and a 10 amp fuse however both are rated for 250v for some reason, it is marked on the board and in the manual for the 10 amp fuse, yet the meter is rated for 1000v Cat III, so...?I was planning on doing a mod to let it accept HRC fuses for the 10 amp, but most of those are 1000v rated, I'm just wondering if it is just an oversight in the manual that the fuse is for 250v or if I should keep it at that. I don't see myself measuring current at high voltage much, if at all except maybe for very small things (like camera flash charging circuits).So, is it a big deal? Does the manual mark them as 250v just because that's what they throw in it at the factory? I don't think I've actually heard of a multimeter that advises not to measure current above a certain voltage.I'm guessing modding the fuse holders and using 1000v 10A and 500ma fuses won't be an issue, but I'm a bit groggy and doubting myself.I'm also wondering if anyone has an idea how much adding an MOV in line with the PTC would affect measurement if I decide to do that.edit: also, what are the size fuses/way I would find the appropriate sized fuse holders for doing that mod? Does it go by fuse dimensions?

author: Wytnucls
author_rank: Super Contributor
timestamp: May 09, 2014, 01:14:05 pm
content: 1000V HRC fuses were not a requirement for CAT III 1000V meters, in the previous IEC61010 regulations.Your meter has the latest PCB, ready for extra protection components. In some markets, the beefy fuses are already installed.For low power stuff, the glass fuses are fine and cheaper to replace when they blow.The board also has a place holder for a spark gap or MOV.I have installed a GDT on my UT71B and haven't noticed any difference in measurements.Fuse clips are 5AG for the 10A fuse. 3AG for the 500mA is ok, depending on the selected fuse.

author: XOIIO
author_rank: Super Contributor
timestamp: May 09, 2014, 01:19:56 pm
content: Quote from: Wytnucls on May 09, 2014, 01:14:05 pmYeah I was hoping mine would come beefed up. Thanks for the fuse holder sizes, I'll order some since the local store doesn't carry any, and good to see that those are rated for 1kv, guess it's just whatever they toss in. I am curious if the manual for that one is the same or if they change it for those fuses.

author: XOIIO
author_rank: Super Contributor
timestamp: May 09, 2014, 02:03:38 pm
content: I think another mod I will do is changing the piezo at some point, this one sometimes gets scratchy and sounds horrible, I might bit a small two pin one on the board instead.edit: unsure if this are the right sizes, digikey doesn't list them in ag size, I can measure the small fuse with my calipers to be sure but I don't have a larger one.http://www.digikey.ca/product-detail/en/01020071Z/F3781-ND/2498889http://www.digikey.ca/product-detail/en/00300210N/F3304-ND/1210611

author: davidefa
author_rank: Contributor
timestamp: May 09, 2014, 04:21:01 pm
content: The 5ag fuse is a 10mm diameter fuse ( like the 125 series of littlefuse )http://www.digikey.ca/product-search/en?s=14251&FV=fff4000a%2Cfff8003e&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

author: XOIIO
author_rank: Super Contributor
timestamp: May 09, 2014, 04:22:06 pm
content: Quote from: davidefa on May 09, 2014, 04:21:01 pmAh alright, thanks. That's certainly a price increase from 5mm to 10