Most precise fuses? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 04:21:19 am
content: What are the most precise fuses that are or were made?I found these interesting oneshttps://www.littelfuse.com/assetdocs/littelfuse_fuse_272_273_274_278_279_datasheet.pdf?assetguid=06e35cc6-24d4-4aa6-a45e-ceb2642de017They go under the name of very fast blow.But there is little details about part to part variation and stuff like that.Just how precise can you make a fuse in terms of variation? I.e. if it was hooked up to metrology grade power supply and loadI am just curious I don't have an application. And I mean the fuses that only work once not resetting stuff

author: jonpaul
author_rank: Super Contributor
timestamp: June 03, 2025, 06:01:13 am
content: see Littlefuse and Bussman for fuse specs and tolerances.+/- 50% is not unusual on IsqT or I maxJon

author: indeterminate
author_rank: Regular Contributor
timestamp: June 03, 2025, 06:19:49 am
content: There are to many environmental variables.Ambient temperature, humidity , air speed, conduction from the fuse mountingsall of these will alter how fast the peas of metal melts and opens the circuit.

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 06:21:11 am
content: But does anyone or did anyone do anything more precise ? Say for 100 fuses.and I don't see the spec on their configurator for accuracy.And that would be another interesting spec, drift based on ambient temperature and also steady current between fusesI.e.Fuse @ 25C with 0mA flowing before overloadFuse @ 50C with 0mA flowing before overloadFuse at 25C with 500mA flowing before overloadand so on and so on

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 06:26:30 am
content: Maybe dave jones can buy 1000 fuses and do a studythe boring resistor video was actually very interesting and I am sure fuses would be even more interesting

author: tom66
author_rank: Super Contributor
timestamp: June 03, 2025, 09:29:27 am
content: Define 'precision'. Are you expecting the fuse to blow consistently at 2mA, say, +/-10%? If so, you cannot design a wire-based fuse to do so, since ambient temperature and lead temperature of the component will change the trip current. A fuse manufacturer can probably guarantee that the fuse will have a very consistent I2S at +25°C, but they cannot guarantee that same performance at +50°C. If you need precision, you need e-Fuses, which measure the exact current and trip with a reset function. e-Fuses are used in some modern cars, a good example is all new Tesla models, this allows for precision current limits for circuits to be established which means that wiring does not have to be rated to survive a short circuit before the fuse can pop, reducing the weight and cost of wiring looms. You could not do that with normal fuses, especially not in an automotive environment varying from ambient temperatures of -30°C to +50°C.

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 01:36:28 pm
content: exactly, how many percent the spread is @ some fixed temperature (more defined thenvery)

author: temperance
author_rank: Super Contributor
timestamp: June 03, 2025, 03:08:32 pm
content: Fuses are not meant to precisely protect something. Fuses are meant to stop equipment failing in a catastrophic way.While fuses might seem like simple components I personally find them one of the most difficult things to use. A good example is given TAE. The example is to protect a transformer. The fuse must be able to withstand some inrush current many many times and at the same time protect the transformer from overheating when something goes wrong.QuoteAre you talking about the video with the frozen fuses?

author: TimFox
author_rank: Super Contributor
timestamp: June 03, 2025, 06:00:34 pm
content: A specification of precision usually implies measurement by automated equipment before leaving the factory.For example, measuring the actual resistance of resistors with high-speed equipment.That would seem to be impossible for a "destructive" specification, such as time to blow as a function of current.Of course, it's straightforward to specify that the fuse willnotblow at a given current.

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 08:39:14 pm
content: I mean a study like the one where he made a bell curve of resistor values.I think seeing the test results from 100+ fuse tests on the same fuse would be really interesting to see.Might be enough just to overlay 100 traces from the scope measuring current and voltage

author: TimFox
author_rank: Super Contributor
timestamp: June 03, 2025, 08:45:02 pm
content: Quote from: coppercone2 on June 03, 2025, 08:39:14 pmThe manufacturer could certainly do a series of tests on samples from a manufacturing lot, testing to destruction.To what purpose? Knowing the guaranteed non-blowing current is important, but an estimate of time-to-blow need not be precise.

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 09:21:45 pm
content: don't you want to know?

author: thm_w
author_rank: Super Contributor
timestamp: June 03, 2025, 09:36:59 pm
content: Looking at the temperature rating curve already having a 10-20% swing tells you a bit. I don't think there is too much to be done to avoid ambient temperature effects, unless you go to extreme levels and temperature control the fuse environment.Quote from: coppercone2 on June 03, 2025, 04:21:19 amBut nothing is stopping you from using a digital fuse once, and it is going to be far more precise, with easy to find specifications.

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 09:51:16 pm
content: I want to know how similar the wires melt , my interest is specific

author: nctnico
author_rank: Super Contributor
timestamp: June 03, 2025, 11:05:34 pm
content: Quote from: coppercone2 on June 03, 2025, 09:51:16 pmThat is going to be really expensive, really quick. Think about aging, salt water, air pollution, corrosion, etc. It will take a crapload of expensive equipment and testing many samples for years.

author: coppercone2
author_rank: Super Contributor
timestamp: June 03, 2025, 11:07:45 pm
content: Depending on how good you want the data. I thought you can get a fuse holder, a switch and do this in an hour at the benchI wonder how many you need for a bell curve to form

author: thm_w
author_rank: Super Contributor
timestamp: June 03, 2025, 11:54:49 pm
content: Some copper data:https://iopscience.iop.org/article/10.1088/2053-1591/ac99bd/pdfBond wire:https://www.researchgate.net/figure/Bond-wire-test-data-for-near-threshold-fusing-current_tbl1_255814217https://www.rfcafe.com/references/articles/gold-bond-wire-report-sandia-labs-sand2013-3715.pdfSome general calculations:https://www.researchgate.net/profile/Vytenis-Babrauskas/publication/286096911_Fusing_of_wires_by_electrical_current/links/5685719808ae051f9af1e0ee/Fusing-of-wires-by-electrical-current.pdfBuying some fuses and measuring would be good to try, but you won't know how accurate the wire diameter was made, if that specific batch was better or worse than another, etc. If you did it with bare wire, you'd have a bit more control over the parameters.