Compilation and comparison of fuses for common multimeters - Page 1
Forum section: electronics / testgear

author: nightfire
author_rank: Frequent Contributor
timestamp: October 15, 2020, 08:33:53 pm
content: Beginning at my last job, I have had some reasons to dive deeper in some characteristics of fuses, namely their behaviour to interrupt a given overcurrent situation- this went to me learning how to calculate with pen and paper (and my trusty HP 48G) short curcuit currents and how to dimension the fuses/breakers for that.(OK, at that last job we routinely were working with circuits and busbars that had NH00 125A fuses on them, our UPS hat NH3 630 Amps fusing or microcontrolled breakers with sometimes up to 1600A rated current)Anyway, as I was going for a good used multimeter on ebay, I also checked for spare fuses and how to get them- and if i could possibly replace them with other manufacturers versions, given that their curves and ratings are equal. Also for having the fuses causing voltage drops (burden voltage), it possibly is of interest how well a fuse is designed resp. which resistance it will employ.My Agilent U1272A for example houses a 11A DMI fuse from SIBA, 1000V with 30 kA breaking capacity, number 50 199 06- and a440 mA SIBA fuse, 1000V, 30 kA, 50 210 06.Note: I really appreciate how Agilent designed the backside- when removed, at the PCB the correct rating/voltage is etched, and at the side of the housing there is a small ramp for a screwdriver to get the fuse out of the holder.What a list could provide as Information:Manufacturer Name of DMM, rated category and Volts, physical dimensions of fuses, type of material (glass, ceramic with sand etc.), rated current, max. breaking capacity, characteristic, power loss at rated current, applications/standards (VDE, UL etc.)Just pulled the datasheet from the manufacturers catalogue, and the 11A fuse is 10x38mm fuse, build with characteristic gR, rated AC/DC 1000V, manufactured in sizes of 0.5A to 16A.Material is sand filled ceramic, rated current 11A, 30 kA max. breaking capacity in 1ms, 1,6 Watts power loss, UL248-13.Interestingly, the smaller 440mA fuse is a 10x35mm size (which is rather uncommon, more widespread are 6,3mmx32mm or 10x38mm), that has no standards to conform to, is given as "Werksnorm", has 0,2W power dissipation, and 980 mOhm resistance according to catalog. Also rated for 30kA breaking capacity. This type is officially rated for AC/DC 1000V, and available in 200mA-440mA.What do you think about such list? Will it be helpful for some people to get proper replacements?

author: nightfire
author_rank: Frequent Contributor
timestamp: October 15, 2020, 08:55:19 pm
content: Just looked at the datasheet of those SIBA puppies and of the bussmann fuses used in lots of Fluke DMM like the 170 series.The 440mA Version from Bussmann will go to work at above 1 Amp, at 1.5A it will take 1.5sec to pre-arc, at 2A we are at 0.05sec and below 2.5A the curve is at the bottom of the chart with 0.01Sec- the SIBA equivalent is at 1.5A with 0.6sec pre-arc, at 2A we are talking 70ms, above that the curve goes not straight down, therefor allowing for short bursts up to 4A within 10ms NOT to blow the fuse.Therefore, depending on the applicaton scenario, and the innards of the measuring device, this behaviour could have some advantages/disadvantages.