PTC (positive Thermo coefficient) device temp ratings.

[martin griffith]

this has alluded me for a while since
i can not seem to find the temperature
at which the manufactures state their
PTC or NTC. etc..
for example
i have a PTC rated for 100 ohms cold!
now what temp is that?
hell, it's 55F here in the shack and i
am cold now! does that apply?
just like to know what temp they are
referring to !

I've only collided with NTC's occasionally, do a search for siemens
matushita B57164 data sheet, gives a lot of numbers, in centigrade,
they seem to be referenced to 25C


martin

 

[John Popelish]

this has alluded me for a while since
i can not seem to find the temperature
at which the manufactures state their
PTC or NTC. etc..
for example
i have a PTC rated for 100 ohms cold!
now what temp is that?
hell, it's 55F here in the shack and i
am cold now! does that apply?
just like to know what temp they are
referring to !

One kind of PTC is essentially a thermal switch that changes from a
low resistance state (that varies very little over a wide range of
temperatures) below the switching temperature to a very much higher
resistance, above the switching temperature. They are intended to
either detect which side of a single temperature they are on (or
provide a very sensitive temperature measurement over a narrow range
of temperatures), or are intended to act as self resetting fuses.

Those intended as fuses are specified in terms of their switch off
time versus current and temperature:
http://www.littelfuse.com/data/en/Data_Sheets/30R.pdf

Those intended as temperature detectors are specified with a curve of
resistance versus temperature, and usually a switching temperature
(the temperature at the steepest point on the resistance curve).
http://www.epcos.com/inf/55/db/ptc_03/01870189.pdf

 

[Jamie]

this has alluded me for a while since
i can not seem to find the temperature
at which the manufactures state their
PTC or NTC. etc..
for example
i have a PTC rated for 100 ohms cold!
now what temp is that?
hell, it's 55F here in the shack and i
am cold now! does that apply?
just like to know what temp they are
referring to !

 

[Rene Tschaggelar]

this has alluded me for a while since
i can not seem to find the temperature
at which the manufactures state their
PTC or NTC. etc..
for example
i have a PTC rated for 100 ohms cold!
now what temp is that?
hell, it's 55F here in the shack and i
am cold now! does that apply?
just like to know what temp they are
referring to !

They refer to 25 DegC, there should be an
online translator to be found on the
internet, I guess.

Rene

 

[Rich The Newsgroup Wacko]

The tires on my car are supposed to be inflated to 28psi when cold, but the
colder I make them, the more air I have to put in. No doubt immersing them
in liquid nitrogen would get them really cold, but I'm a little short on the
liquid form right now, and don't have enough to dip a car tire in. I suppose
I could extrapolate, but I figure inflating my tires to 60psi should be
enough, even when the outside temperature reaches 150K (-190F). That won't
help if I drive down a street covered with liquid helium, but what the
hell - sometimes, you just have to throw caution to the wind.

-- Mike --

Now, there's a concept. The tire bomb. Just drop the tire in a tub of LN2,
and fill it up with air - hey, wait a minute, won't the O2 condense out
at LN2 temps? Hmmm... Anyway, set it where you want the explosion to be,
and walk away. The nitrogen boils off, the air in the tire expands, and,
BLOOEY! ;-p