LM35 R design

[franky]

Hi all,

I'm doing a project for temp. monitoring using LM35DZ the supply is 5V
I don't know what's the sutable R between Vout & ground to aviod self
heating because we can't get Vout with out this R also i need to
adesign to get the range of Vout be from 01 to 0.9 using opamp or
anything else so please could anyone help me

PLZ,
Best regards

 

[mkaras]

Hi all,

I'm doing a project for temp. monitoring using LM35DZ the supply is 5V
I don't know what's the sutable R between Vout & ground to aviod self
heating because we can't get Vout with out this R also i need to
adesign to get the range of Vout be from 01 to 0.9 using opamp or
anything else so please could anyone help me

PLZ,
Best regards

Maybe you would be way better off trying something digital. A part like
the TMP100 from TI is an easy piece of cake to use with its I2C
interface bus, runs on miniscule current, is rather easy to make work
as a temp monitor.

- mkaras

 

[[email protected]]

Hi all,

I'm doing a project for temp. monitoring using LM35DZ the supply is 5V
I don't know what's the sutable R between Vout & ground to aviod self
heating because we can't get Vout with out this R also i need to
a design to get the range of Vout be from 01 to 0.9 using opamp or
anything else so please could anyone help me

According to the data sheet, you don't need any resistance between Vout
and ground.

If you are loading Vout with more than 50pF of capacitance, you wll
want 2k in series with the output to stop it oscillating (Fig.3 on page
7 of the data sheet), or 75R is series with 1uF to ground to do the
same job (Fig. 4 on page 7).

Neither arrangement adds to the self-heating.

http://cache.national.com/ds/LM/LM35.pdf

Your request for a circuit to "get the range of Vout to be from 0.1 to
0.9" isa little unspecific.

Do you want 0.1V to 0.9V? If so, what temperature do you want to
correspond to 0.1V out of your op amp, and what temperature to 0.9V?
The LM35 is perfectly inflexible in generating a specific output
voltage of 10mV per degree C (+/-5mV 2C on up - that is it starts at
20mV+/-5mV at 2C, and goes up 1.0V+/-15mV at 100C.