Can I use a resistor as a fuse?

[shrtrnd]

I don't build 'em, I don't design with 'em, and now I know that zero ohm resistors don't even exist!
I talked to another tech here with 52 years on HP gear (Hewlett Packard/Agilent/Keysight). Like me, he didn't give zero ohm resistors much thought other than replacing them.
He said it's obvious to him, that when a circuit catasrophically fails on a board, the current can increase rapidly, and the zero ohm resistor opens to protect the other boards within the
instrument. So that makes two of us dummies who believe that. A wire doesn't open in that circumstance. So whether it was design intentional or not, that's the effect.

Hello Dennis,
We received the following message from you:
*********************************
Technical question. What is the purpose of the zero ohm resistors in your test and measurement equipment? I'm having a disagreement with a colleague who claims the zero ohm resistor is simply a machine-insertable replacement for a jumper-wire on the printed circuit board. I would like to know if the zero ohm resistor is intended for a specific electronic function, rather than to just make it easier for a machine to pick-up and insert than a thin jumper wire. Thanks, Dennis Jeffrey
*********************************
I apologize, but I'm not aware of any "zero ohm resistors" inserted in our test and measurement equipment. Especially the part about "a machine-insertable replacement for a jumper-wire on the printed circuit board". What circuit board or what Keysight instrument are you referring to? Please let me know so I can get your question to the proper support group. Thanks!

Regards,

Ron Knight
Inside Applications Engineer
Keysight Technologies, Inc.
Americas Technical Contact Center
Online Technical Services
800-829-4444, enter Case ID# 6260093854

 

[KrisBlueNZ]

Can you email Ron a product name and circuit reference so he knows what you're referring to?

 

[shrtrnd]

I'll find something to send him. It looks like he'll then have to send the query to some other 'support group'.
The issue is: I'm still repairing old HP T&M gear. Agilent refused to support (the old) HP gear, as they were only interested in the 'AGILENT' product line.
Their lack of support for the HP line garnered them enough of a bad reputation from people in my line of work, that they canned their CEO, and have now changed their
name again, so the products they produce are not associated with the poor reputation 'Agilent' name.
I don't know how the press releases spin the name change, but that's my opinion.
We are JUST NOW beginning to receive instruments with the Keysight name on them. None of them have crossed my bench yet.
I have no doubt if I reference an HP model, they'll tell me they can't help me. I'll be on the look-out for an Agilent instrument to reference for them, but that might take a while;
I HOPE they'll support the Agilent name for at least a little while. And having never cracked a 'Keysight' instrument open yet, I don't have a "Keysight' product to reference for him.
So don't expect an answer to this anytime soon.
I'll mention, Agilent T&M gear is good; but their reputation with people like me was in the tank because of lack of support, and we were not recommending them for new purchases.

 

[KrisBlueNZ]

So, no conclusive result? Ah well, never mind.

 

[shrtrnd]

Apparently my query went to somebody who directs queries to the various 'support groups' within the organization. What they want is a model number of a specific instrument (not the old Hewlett Packard name), so that my
query can be handed-off to somebody familiar with that specific instrument. Right now, that would mean an instrument with the Keysight name. I would imagine it will be a while before one of these new instruments comes to
me for repair. Hewlett Packard T&M gear is pretty-much compartmented any more to people like me who have been repairing it for years. There is no manufacturer who supports it anymore. Everything I'm familiar with concerning
zero ohm resistors, is associated with old Hewlett Packard test and measurement equipment. My original post suggesting the use of a zero ohm resistor as a potential fuse was inappropriate.
I'll get an answer from Keysight eventually. I just don't think it'll be any time soon. I couldn't figure-out why Agilent would continue to use zero ohm resistors in surface mount, if it was only supposed to be a jumper wire, but one
of the college kid engineers we have here told me they're useful in multi-layer boards. For me, this is just one of those new things I learned, that I'm still gathering information on for my own edification.

 

[elebish]

What may measure 'zero' ohms may not be true zero. Use a 5 1/2 digit 4 lead ohmmeter and check again. Maybe we can call them fuse-able wires. The type of metal these are made from could be part of the answer. Ed.

 

[KrisBlueNZ]

What may measure 'zero' ohms may not be true zero.

Of course, it won't. Unless it's a superconductor, maybe!

Maybe we can call them fuse-able wires.

You mean, fuses?

What's the rating? They're only marked with a black stripe.

 

[garublador]

I couldn't figure-out why Agilent would continue to use zero ohm resistors in surface mount, if it was only supposed to be a jumper wire, but one
of the college kid engineers we have here told me they're useful in multi-layer boards. For me, this is just one of those new things I learned, that I'm still gathering information on for my own edification.

I'm new to the forum, but I work in PCB design so I though I'd give my insight.

We generally use 0 ohm resistors (almost exclusively SMT) for two main reasons.

First, to allow multiple options. You might want a signal to go two different places depending on the end product or your might have some expensive circuitry that might or might not be needed in the final design that you would like to have the option to bypass.

Second, you don't know if a different component will be required. Once you get to compliance testing (FCC, IC, UL, etc.) you might find that extra components are required. You might need a different value resistor for signal integrity or a ferrite bead to help with EMI that you won't know about until you try it. Then once the unit passes you figure that spinning and testing the board one time (and hoping that it's OK with the compliance agencies) to get rid of the resistors would cost more than 20 years worth of 0 ohm resistors so you just leave them on there.

 

[KrisBlueNZ]

Hi garublador and welcome to Electronics Point

Please, introduce yourself on the thread at https://www.electronicspoint.com/threads/hello-welcome-introduce-yourself.223920