Just to add to the confusion I bought an electrical appliance the other day. In the instruction manual it said "the appliance is supplied as standard with a 5 Amp fuse. If this blows it should be replaced it with a 13A fuse". I don't understand quite why even now. Perhaps they'd run out of 13A fuses... This was in the mass produced printed instructions BTW!!!! If anyone is interested I can pull out the maker and model.... I can't believe it was just the old adage "if the fuse blows use a bigger one". I've seen enough domestic fuse boxes with 1/4" nails for fuses :( I'm not as green as I'm cabbage looking, I just can't believe someone responsible for a electronics firm would actually write this without good reason (e.g. use of 110v rather than 240v on a given load) Ben ----- Original Message ----- From: "Dave Tweed" To: Sent: Friday, March 14, 2003 2:19 AM Subject: Re: [OT]: Radio Shack > Alex Kilpatrick wrote: > > It is a digital meter. The 100 mA fuse is probably not there to prevent > > a fire. :-) > > Actually, it is. It's for when you forget that the meter is in current mode > and you put it across a voltage source. The fuse prevents the test leads > from melting in your hands. A 500 mA fuse works just as well as a 100 mA > fuse for this purpose. > > > I assume it protects sensitive electronics that measure small current. > > The meter will measure down to uA. > > It's actually fairly easy to protect the electronics from overvoltage > faults. You need to do this anyway, as the fuse cannot possibly blow > quickly enough to protect them. > > I'll grant you that many RS employees are fairly dim bulbs, but in this > particular case, he did *not* give you bad advice. > > As far as being "horrified" about a change from a 5A to a 6.5A fuse, > there's the QC point of view and the engineering point of view. From the > QC point of view, it is manufacturing's responsibility to produce the > product that engineering specified. *Any* deviation is a cause for concern. > > However, from an engineering point of view, fuses are very sloppy > devices. If you've ever looked at the percent overload vs. opening time > curve for a typical fuse, you'd understand this. They don't even specify a > minimum opening time, just a maximum for certain levels of overload. They > sometimes even promise that the fuse *won't* open for certain small > overloads (like 125%), so you know what kind of design margin you have. > The actual difference between a 5A fuse and a 6.5A fuse is way down in the > noise. > > -- Dave Tweed > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads