+Vs for LM35 temperature sensor?

[Quercus]

Hi there... I'm playing with a LM35 temperature sensor and having some
trouble with the imput voltage.

It is supposed to work fine between 4V and +20V and to return 10mV/şC
but as soon as I feed it with 4.8, 7.8, 5.5 or 9 volts (I've tryied with
several batteries and phone chargers to get those voltages) my
multimeter reads around 2V, that keeps growing until the sensors
overheats and breaks :-(

I've read the specs sheet from National Semiconductor about temperature
and voltage limits, and this is not supposed to break down so easily.
May be the sensor is bad, but I've tryied with 3 of them and always have
the same result.

My circuit is so simple right now, only +Vs and ground and a multimeter
to read Vout. (I've tried setting some load with a resistor and a
capacitor in paralell, and same behaviour)...

Anyone with experience with this LM35 could assist me?

ANY help would be great! I'm trying to design a temperature regulated
fan and I do need a temperature sensor in şC.

Thanks in advance.

-Quercus-

 

[William P.N. Smith]

Quercus <quercus@nosomos.org> wrote:

It is supposed to work fine between 4V and +20V and to return 10mV/şC
but as soon as I feed it with 4.8, 7.8, 5.5 or 9 volts (I've tryied with
several batteries and phone chargers to get those voltages) my
multimeter reads around 2V, that keeps growing until the sensors
overheats and breaks :-(

According to http://www.national.com/ds/LM/LM35.pdf it should work OK
without bypass caps or anything exotic in terms of connection or such.
A 2V output means 200 degrees C, though, so you've either got a bad
batch or you are connecting them wrong (or it's really hot where you
are... 8*)

--
William Smith
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[Quercus]

William P.N. Smith escribió:

Quercus <quercus@nosomos.org> wrote:

It is supposed to work fine between 4V and +20V and to return 10mV/şC
but as soon as I feed it with 4.8, 7.8, 5.5 or 9 volts (I've tryied with
several batteries and phone chargers to get those voltages) my
multimeter reads around 2V, that keeps growing until the sensors
overheats and breaks :-(


According to http://www.national.com/ds/LM/LM35.pdf it should work OK
without bypass caps or anything exotic in terms of connection or such.
A 2V output means 200 degrees C, though, so you've either got a bad
batch or you are connecting them wrong (or it's really hot where you
are... 8*)

Yep, there was some kind of short circuit in other component in my
circuit, with that replaced now the sensors work great (not that 200şC
anymore, hehehe

-Quercus-