Metal film resistor stability over time

[Bill Bowden]

What resistance change can be expected over time using 5% metal film
1/4 watt resistors?

If I select a couple 5% metal film resistors to use in series to get a
close 1% value, how stable will the resistor value be over a couple
year period?

Are 1% resistors more stable in terms of resistance change over time
than 5% metal film resistors?

Thanks,

-Bill

 

[Dan Hollands]

resistance change over time is generally not a concern unless the resistor
is stressed by overheating. Some data sheets do give informaion on this.
Generally of much more significant concern is resistance change with
temperture. If have circuit that requires a stable resistance but is used
in an environment that has large temperature changes the changes due to
temperature far exceed the change due to time. Again data sheets define
temperature stability. High stability costs more money.

The cost between 5% and 1% metal film these days is negligable for most
applications Why not just by 1% instead of going to the trouble of selecting
5%. Are you sure the measuring instrument you use to measure the resistors
is accurate to 1%?

Dan

--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
[email protected]
www.QuickScoreRace.com

 

[[email protected]]

While I can't answer your question in specifics, I worked in a CRG
(customer returned goods) dept. for Collins Radio, where we had a lot
of older equipment come back for repair. The one trend I noticed is
carbon film resistors tended upward over time (and with internal
heating), sometimes quite a bit over their rated value.

If you're the same gentleman that runs the hobby circuits website,
thank you. Lot of good stuff in there.

 

[[email protected]]

While I can't answer your question in specifics, I worked in a CRG
(customer returned goods) dept. for Collins Radio, where we had a lot
of older equipment come back for repair. The one trend I noticed is
carbon film resistors tended upward over time (and with internal
heating), sometimes quite a bit over their rated value.

If you're the same gentleman that runs the hobby circuits website,
thank you. Lot of good stuff in there.

 

[Jasen Betts]

What resistance change can be expected over time using 5% metal film
1/4 watt resistors?

If I select a couple 5% metal film resistors to use in series to get a
close 1% value, how stable will the resistor value be over a couple
year period?

Are 1% resistors more stable in terms of resistance change over time
than 5% metal film resistors?

Thanks,

It's possiblle that the 5% resisters are made while the guy is
adjusting the machine to the 1% accuracy needed to make 1% resistors

OTOH the metallic material in the 1% units may have a better temperature
coefficient.

if thermal stability is not an issue the 5% kludge may be sufficient,
but otherwise use 1% parts.

 

[Michael A. Terrell]

While I can't answer your question in specifics, I worked in a CRG
(customer returned goods) dept. for Collins Radio, where we had a lot
of older equipment come back for repair. The one trend I noticed is
carbon film resistors tended upward over time (and with internal
heating), sometimes quite a bit over their rated value.

If you're the same gentleman that runs the hobby circuits website,
thank you. Lot of good stuff in there.

I serviced some Rockwell/Collins C-band equipment that ran so hot
that the fiberglass turned black over a large part of the PC board
because there wasn't enough airflow. The equipment was used in a 65
degree room, yet the cases were warm to the touch. The didn't use any
fans to circulate air inside the aluminum box, and it caused lots of
damage.

 

[John - KD5YI]

What resistance change can be expected over time using 5% metal film
1/4 watt resistors?

If I select a couple 5% metal film resistors to use in series to get a
close 1% value, how stable will the resistor value be over a couple
year period?

Are 1% resistors more stable in terms of resistance change over time
than 5% metal film resistors?

Thanks,

-Bill

http://www.vishay.com/resistors-discrete/metal-film/related#technt

Get the "Resistors - General" PDF document near the bottom of the page. I
looked at the document examples briefly and they did not indicate that 1% or
5% tolerance had any effect on long term stability. Temperature over time
apparently has the greatest effect regardless of initial tolerance.

Disclaimer: I only read part of it.

Cheers,
John