Some excellent points about cost. But how much could a zero ohm resistor, basically a jumper cost? Plus, what's the ±% of a jumper?

I can see the advantage of a zero ohm resistor because it can easily be machine placed; which lends itself to cost saving as opposed to having a technician solder a jumper wire on there.

why carry the inventory?

I'm with you on that.

 

Plus, what's the ±% of a jumper?

I've loved this question since the first time it crossed my mind. Who would think you'd have to watch out for a division-by-zero error when trying to spec a tolerance on the simplest part imaginable?!

Anyway, I got curious and looked some up to see. A random sample I picked from Digikey lists 0.05 ohm max for their 0 ohm (jumper) resistors. So, of course it's not a percentage based tolerance, just a max resistance limit.

 

Used to work for Northrop Grumman Space Technologies. Receiving inspector. We'd receive these ceramic plates about 2 inches square. We'd check them to the print and data sheets. Once passed they went out for gold plating. Sometimes they'd come back broken. Either a corner broken off or completely broken in half. Of course those are rejected. Writing the NCMR they wanted an "IS" and "SHOULD BE" statement. I thought it was rather painfully obvious when they came back broken that they were "Broken". So when I rejected them I'd get my NCMR back because it didn't have an "IS" and "SHOULD BE" statement. I got so damned frustrated with the engineers I started putting "IS BROKEN". "SHOULD BE NOT BROKEN".

It was a fun job while it lasted. Some people just have no grey matter. Just why they put a 100Ω resistor in series seems rather obvious to me - it's what they had on hand that would work for the cheapest cost. That's often the biggest motivator in any business. Save that buck. But then again I've worked for companies that stepped over dollars trying to pick up dimes. Gosh I get irritated by stupidity.

 

I've loved this question since the first time it crossed my mind. Who would think you'd have to watch out for a division-by-zero error when trying to spec a tolerance on the simplest part imaginable?!

Anyway, I got curious and looked some up to see. A random sample I picked from Digikey lists 0.05 ohm max for their 0 ohm (jumper) resistors. So, of course it's not a percentage based tolerance, just a max resistance limit.

he big deal of "why carry the inventory is that with one PCB that could be assembled two different ways there had to be something soldered between those two pads. AND it had to look different enough so that it could be recognized as the correct part by an illiterate laborer. And so the "101"s adequately different from the "243" .