Re: EOL's

[Robert L Bass <sales@xxxxxxxxxxxxxxxxxxxxx>]

> If you begin with a resistor with a 20% tolerance (no tolerance band),
> and with some age and heat, the carbon in it can change it's
> resistive/conductive properties...

No Al.  That is not correct.  Tolerance is a measure of the
precision of the resistor in manufacturing.  It does not mean
that the resistor will change over time.

Resistors are never made to the exact value indicated by the
color codes.  Manufacturers use the tolerance color band to tell
you just how accurately the resistor was made.  It is a
measurement of the imperfections.  Gold = within 5% of dead-on.
Silver = within 10%.  In other words, the tolerance band
indicates the range of possible values that a given resistor may
have.  For example, a resistor with three red bands and one gold
band is rated at 2200 Ohms but it can actually read anywhere from
2090 to 2310 Ohms.  Whatever its value was when made, it will
remain at that same value permanently.

To determine the exact range that the resistor may be, take the
value of the resistor and multiply it by 5%, 10%, or 20% for
gold, silver or no tolerance band, respectively.

> If you really want to control this better, try either 10% tolerant
> resistors (silver tolerance band) or better yet 5% (gold tolerance
> band) resistors.

The above statement is based upon a misunderstanding of resistor
tolerance.

If you really want to be picky, use 5-band resistors but have fun
finding an alarm manufacturer that supplies them.  3-Band and
5-band resistors do exist, though they're not appropriate for use
in alarm circuits.

It is highly unlikely that the gentleman has a 20% tolerance
resistor but even if he did that would not mean that the carbon
is more likely to change value.

--

Regards,
Robert L Bass

Bass Burglar Alarms
The Online DIY Store
http://www.BassBurglarAlarms.com

--

Never underestimate the power of very stupid people in large
groups.