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Problem encountered when using LM35DZ

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cjhaw

New Member
Hi, I am new in using the LM35DZ. I had encountered when measuring a temperature of boiled water by using the connection of basic centrigrade temperature sensor (Fig 1) from LM35 data sheet. Supposed the temperature measured by thermometer is more than 90 'C. But the measured temperature from LM35 is 55 'C which is shown in multimeter 550 mV.

Is there any solution to improve the result? I hope that I can get help from you all.

Thank you.
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi, I am new in using the LM35DZ. I had encountered when measuring a temperature of boiled water by using the connection of basic centrigrade temperature sensor (Fig 1) from LM35 data sheet. Supposed the temperature measured by thermometer is more than 90 'C. But the measured temperature from LM35 is 55 'C which is shown in multimeter 550 mV.

Is there any solution to improve the result? I hope that I can get help from you all.

Thank you.

hi,:)
I assume you powered the LM35 from 5V thru 9v.??

How did you bring the LM35 body into contact with the boiling water.?

Usually they are accurate to +/-0.5C,
 

atferrari

Well-Known Member
You did the test at sea level or up there somewhere in the mountains?
 

cjhaw

New Member
hi,:)
I assume you powered the LM35 from 5V thru 9v.??

How did you bring the LM35 body into contact with the boiling water.?

Usually they are accurate to +/-0.5C,

Hi, I used power supply with only 2V to tune until 280mV which indicate the room temperature. I didnt tune it to 4V or more because the multimeter will show higher value of voltage output which is not same as room temperature. just contact the top surface of LM35 on the surface of aluminium cup. I also tried to immersed the body of LM35 into the boiled water. Is there any solution?
 

cjhaw

New Member
You did the test at sea level or up there somewhere in the mountains?

I did the experiment with the room temperature of 28 'C, sea level. I also used thermometer to measure the boiled water. By right the divice should show the result near to the thermometer. Thanks.
 
Hi,

Are you applying sufficient supply voltage?

9032-LM35_1.png


9033-LM35_2.png
 

cjhaw

New Member
Hi,

Are you applying sufficient supply voltage?

9035-LM35_1.png


9036-LM35_2.png


Hai, thank you for the post. The figure in attachment is the 2 ways I used to connect the LM35 to power supply. The left one show the direct connect of LM35 legs to the power supply. The second one I just connect the two V+ and V- to power supply then from the power supply, the V- connect to GND.

I actually try to follow the value in data sheet. But with the connection, when I tuned my voltage input to 4V, I need higher current (could be up to 0.3 A) and the LM35 itself is getting very hot and give high voltage output than expected. Is there anything wrong with my connection? Thanks.
 

Attachments

  • lm35 connection.PNG
    lm35 connection.PNG
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ericgibbs

Well-Known Member
Most Helpful Member
Hai, thank you for the post. The figure below is the 2 ways I used to connect the LM35 to power supply. I actually try to follow the value in data sheet. But with the connection, when I tuned my voltage input to 4V, I need higher current (could be up to 0.3 A) and the LM35 itself is getting very hot and give high voltage output than expected. Is there anything wrong with my connection?

The LM35 if connected correctly only draws microamps and shouldnt even get warm at 5V.

Check that you have read the LM35 correctly from the datasheet.:)

We cannot access an image on your PC, scroll down on the Reply window and use the ' manage attachments ' button
 
Last edited:

AllVol

New Member
I use the LM34, TO-92 package (same device except it reads in F instead of C) right out of the box with regulated 5 volts. Temp readout on DMM will constantly track within .5 degrees my $500 indoor and outdoor thermometers.

Generally, if a part is behaving irradically, it isn't the part.
 

cjhaw

New Member
eric: you are fast replying while I manage to find the options. Yah, should be in microamps but when I increasing the voltage the CC light is on back from power supply. Is there any problems? Or is it better if I use three 1.5 V of battery to do the measure? The attachment is the power supply I used.
 

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  • power supply.JPG
    power supply.JPG
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AllVol

New Member
I posted my connection of LM35 as well.

Where did you get those connections? Attached is the proper connection from the LM35 data sheet. Very simple. Plus and ground from your power supply, DMM red probe to out and black probe to ground. No problem.
 

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  • LM35 connections.GIF
    LM35 connections.GIF
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atferrari

Well-Known Member

cjhaw

New Member
Hi there, thank you for all of you help. I made the correction of connection of the circuit.

Actually, I made two mistakes before that. First is I thought the LM35DZ in data sheet is top view (didn’t notice there is a ‘BOTTOM VIEW’ there. The second mistake is I misunderstood the connection shown in Figure 1. Next time I will be more careful.

The V+ of LM35DZ should connect to + at power supply whereas the GND connected to -. Then use multimeter to connect at GND and Vout of the LM35DZ. Logic result will then be shown on the multimeter. Haha.

Many thanks for you all. Have a nice day:)
 

cjhaw

New Member
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