All,

 FYI, yes this works and rather well I might add.  We used this exact
 method when I worked at TI to temperature compensate a microcontroller
 clock frequency so as to maintain correct time as an RTC.   It worked
 well.
 IIRC, the change for a 1N914 (1N4148 too I'm sure) is 1.4mV/degree C.
 So you can tell a temperature within about 1.5 degrees if everything
 is ideal.   A more practical value is about 3 degrees.   This was
 determined from our experimentation with the diode as mentioned above.

                                                Regards,

                                                  Jim


>>I saw a circuit on the web that use 1N4148 as car water temperature
>>probe. is it accurate? never heard about this method before.
>
> Any transistor or diode junction can be used as a temperature sensor,
> as the voltage drop across the junction has a well defined change in
> voltage with temperature.
>
> Companies like Maxim make chips that will use a transistor as a
> temperature sensor for use inside PC's, as the Pentium chips have a
> transistor temperature sensor built in to allow control of fans.
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads