# Temperature sensing

Discussion in 'The Projects Forum' started by perzade, Apr 5, 2012.

Jan 30, 2011
4
0
I'm having problem in biasing the LM35 temperature IC. The multimeter reads 0.6v for a bias of 5v & output is also erroneous.Is there any proper biasing circuit for the IC or a direct supply of 5v will work???

2. ### #12 Expert

Nov 30, 2010
16,705
7,358
Judging from your schematic, I'd say just give the LM35 five volts and let it output what it wants to output.

3. ### tracecom AAC Fanatic!

Apr 16, 2010
3,880
1,396
I don't see a schematic, however the LM35 requires no special "biasing." It operates on 4-30 volts, and its output is independent of the input voltage within that range. The output is a linear function of the temperature sensed by the LM35.

4. ### #12 Expert

Nov 30, 2010
16,705
7,358
I don't see a schematic either. I was trying to get perzade to post one.

5. ### wayneh Expert

Sep 9, 2010
12,406
3,256
A picture might be even better. Like anything with 3 pins, it's easy to get them out of order. Been there, done it. Amazingly, the LM35 can survive a mistake at 5V, but not more. I suggest double checking the pinout. Also, the output really should be shown a small load, and a meter may not be enough.

6. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
Its simple apply regulated +5 volt dc to pin 1 and connect pin 3 to GND and read the voltage between pin 2 and GND.

If you don't get a proper out put then most probably the IC is damaged,for proper pin out check the datasheet.

Good Luck

7. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
Remember the output scale factor for LM35 is about 20mV/C i.e.. 20 milli volt per degree centigrade (Celsius).So if the temperature is 30 degree centigrade then the output will be 30 * 20 = 600mV i.e.. 0.6V as your meter is showing.

Good Luck

8. ### wayneh Expert

Sep 9, 2010
12,406
3,256
Ummm.... Pretty sure it's 10mV per °C, not 20

9. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
Sorry ,yes its 10mV,I was thinking about LM37 which I work with most...