[sdiy] really basic question .. tolerance

[Brock Russell]

Mike wrote:
>I had occasion to measure  around one hundred each of several
>10K to 100K one-percent resistor  values from a single manufacturer, and
>around 90 percent of them were <almost> one percent below the listed
>value. As a calibration check I used several 0.01 percent resistors. The
>one-percenter distribution was skewed in one direction, although all
>were within the rated tolerance. Perhaps they were reject 0.1
>percenters...

They are probably just new. The resistance of spiral cut metal film
resistors increases over time so they are made low to maximize life
within tolerance. Measure them in ten years and they will probably be
spot on.

This info tidbit courtesy of my college instructor Ralph, whose first gig
out of university was making and selling precision resistors for HP.

Brock