How to deal with offset in LM35 instrumentation system with TC7107

Thread Starter

agnimusayoti

Joined Apr 26, 2021
14
Hi. I have an electronic project. In my project, I can display measurement's result from LM35 with TC7107 with 1°C resolution. Oh, almost forgot, my system is simulated in Proteus 8.6. When I increase the resolution of my system, I have a problem with offset. If the temperature is below 80°C, my system have offset 2°C. For example, if the temperature is 50,1°C, the output of LM35 is 0.503 V. With TC7107, I use 1V reference and just use 3 last digit. So the result is 50.3°C. how can I fix this problem? Thanks
 

Thread Starter

agnimusayoti

Joined Apr 26, 2021
14
I have idea to use voltage divider. But the output has voltage drop if I use potentiometer. So i try to solve the problem by using voltage follower with OP AMP LM741. Still the problem exist because the output of opamp is not same with the output of sensor. below is my circuit.
1620795445863.png
 

LowQCab

Joined Nov 6, 2012
510
The LM-741 will not operate in a linear-manner with its Inputs near Ground.
Use a LT1632IN8 instead.
The LM35, and the LT1632IN8 will operate on a ~5-Volt supply with no problems.
The Circuit below will let you achieve anything you need.
After you get everything adjusted to your satisfaction,
the Trim-Pots can be replaced with 0.5% Resistors.

Edited ........ Precision Resistors needed an extra zero.
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Temp Cicuit FLAT .png
 
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