LM35 data aquisation issue

Status
Not open for further replies.
D

dharanikumarsrvn

Junior Member level 1
Joined
Oct 22, 2012
Messages
15
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Visit site
Activity points
1,401
i am using a LM35 Ic temperature sensor along with a ADC to detect temperature. LM35 will give a output of 0.35V for 35degC (0.01V for 1degC). The problem i am facing is whenever i connect the LM35 ouput pin to ADC input channel, the output of the LM35 changes to 2.3V. Is there any loading effect by the ADC which causes the change in LM35 output?
 

Is the ADC a stand-alone device or is it part of a microcontroller?

In the latter case, are you setting the port correctly? With today's controllers, most ports can be congifured as input/outputs, digital/analog, and can have pullups/pulldowns.

A simple experiment you can do is substitute the sensor with a potentiomenter, and verify the behavior.
 
Last edited:

I implemented a similar circuit couple of years ago, and it worked correctly I don't think it is a loading problem
 
Reactions: v!gor

    V

    v!gor

    Points: 2
    Helpful Answer Positive Rating
apologies for my late response. I have replaced sensor with a potentiometer and it works fine. My ADC is a part of Chipon CC2430 Microcontroller (a zigebee wireless transreciever). The Vcc supply to the LM35 and GND are drawn from the microcontroller lines itself.
 

As far as I can recall , the LM35 could be prone to oscillations. check this is not happening.(I assume you have a scope) Check the rf from the tranciever is not
screwing up the LM35 as well. Put plenty of filtering on the supply lines , maybe a ferrite bead and cap will do.
Just my 2c :0)
Cheers
Neddie
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…