More on CHT probe replacement

Jim Burns wrote:

Not having a background in electronics, what ultimate difference would a
resistor of higher wattage rating have on the circuit, the gauge, or the
probe? If the circuit is only drawing mA's, 1) are there "smaller" mA rated
82ohm resistors available or 2) with a mA rated resistor would the required
ohm rating change? Forgive my ignorance regarding resistors, I basically
understand what they do, but do not know the implications of the
sizes/capacities.

I don't have a background in electronics, either, but I'd think 3 watts is way
overkill from an electrical point of view, *but* a higher power rated resistor
is also more robust from a mechanical point of view, and may stand up better to
the vibration environment. Just an idea from an ignorant observer.

Dave

I don't have a background in electronics, either, but I'd think 3 watts is
way
overkill from an electrical point of view, *but* a higher power rated
resistor
is also more robust from a mechanical point of view, and may stand up
better to
the vibration environment. Just an idea from an ignorant observer.

Dave

You summed up my thinking pretty close. I'm thinking if 3W is overkill,
what are the downsides of it? Shorter probe life? shorter gauge life?
shorter resistor life? If it doesn't detrimentally effect the operation of
either the probe or the gauge and the life of the components isn't
compromised, then the only downside I see is about $0.10. But like I said,
I don't have much knowledge in this area but I'm willing to learn so I defer
to the pros.

Thanks
Jim

As long as the higher wattage resistor fits physically and is the
appropriate resistance (82 ohms in this case), it will work just
fine... It will be just loafing at a small fraction of a watt and so
should never 'burn out from thermal stress.... Physically larger is
usually more mechanically robust, as Dave surmises...

Resistors start at 1/8 watt at most electronic suppliers and go up into
the hundreds of watts... The larger units will not be available in all
resistances, especially in the megohm range... For what you need it
in the airplane, a wirewound "flameproof" of 2 watts is fine...

denny