Load Cell Amplifier Needed

[asimzia]

Hi i am Electronics Engineering student. I am using 10Kg load cells in my final year project. But the problem is that the Load cells give very small output. My load cell gives just 0.5mV/Kg change at its output and i need to give it to microcontroller. So it needs to be amplified first.

I need a suitable amplifier for my Load Cell.

Can any one help ?????

 

[ashistc]

If you still want then reply.

 

[CranKpin]

I need to know, can anyone help?

 

[FvM]

Chapter 4 of the ADI Op Amp Applications Handbook has a detailed discussion of bridge amplifiers. https://www.analog.com/library/analogDialogue/archives/39-05/op_amp_applications_handbook.html

Most people are using an instrumentation amplifier as a simple single chip solution.

You also should pay attention to the "Similar Threads" tab at the bootom of this page. Or perform a search.

 

[CranKpin]

thnx for your reply FvM. I am a bit new to this site,although I joined long before, and still browsing through all the threads. Its an ocean out there.


I want to bother you guys once more. I am doing a project using a 100kg platform load cell. I can amplify my output voltage easily with an instrumentation amplifier. But my problem is elsewhere. I want use the output voltage with a atmega16 microcontroller. Now when I use power supply to power both uC and Amplifier, the amplifier shows bias voltage instead of showing the amplified voltage at output.

This happens irrespective of whether i connect the output to uC's analog input or not.

I am using a 12volt DC supply to power amplifier and using a 7805 to supply 5 volt to uC. Can you guys tell what I am doing wrong? Or suggest me something else?

---------- Post added at 07:44 ---------- Previous post was at 06:57 ----------

I am not using a chip, i made the instrumentation amplifier my self. A differential amplifier gives the problem.

 

[FvM]

Now when I use power supply to power both uC and Amplifier, the amplifier shows bias voltage instead of showing the amplified voltage at output.

I don't understand which problem you're addressing here. You should show a circuit schematic.

 

[CranKpin]

Hey FvM

here is the circuit diagram. But I am sorry I had to give u a hand drawn copy. Let me know if it is not legible.





The +12v is supplied by a single power supply (Adapter).

If I do not connect the uC via a 7805 on the circuit, the amplifier works perfectly.

But the moment I connect the uC in the circuit, (I mean I provide +12v to the 7805, subsequently supplying 5v to uC), the amplifier output shows bias voltage (~+11v).

It is to be noted that it doesnt matter if the output of the amplifier is connected to the uC, happens all the time.


If I use two separate power supply (adapters) the circuit works fine but then I cannot provide the uC with valid aref signal.


I hope I managed to explain the problem to you.

 

[CranKpin]

So, in short the problem is

I am not getting amplified output in the amplifier output, rather getting constant ~+11 volts.


My gain settings should show an amplified voltage between 0-5v.