How to get Brain Waves with AD620 instrumentation amplifier?

Thread Starter

Serhat Özyıldız

Joined Dec 26, 2018
4
Hello.
I am trying to observe brain waves(beta) with AD620 instrumentation amplifier.
The beta waves’ amplitude are around 20-200uV. I want to make it around 0-5V
What should gain resistance has to be around?
I have tried to have x25, x50 gains with 1Kohm, 500ohm. Output of AD620 I didn’t get any signals.
If anybody have an idea about these, can help me Please?
Thanks.
 

danadak

Joined Mar 10, 2018
3,573
The G you have at 500 ohms is ~ 100. As jpanhalt points out,
for min signal that's results in 20 mV.

Do you have a test source to gen 20 uV, 200uV.... ? Thats easily
done with a processor and a DAC being fed by a look up table.

Also are you using 10X or 1X scope probe (you should use 1X),
and what is scope max sensitivity ? Also are you using DSO or analog
scope ? If DSO have you done the G correction utility in scope
to compensate for the probe response. Every little bit of correction
counts.

What are you getting for a signal ? Scope shot ?

Regards, Dana.
 
Last edited:

Thread Starter

Serhat Özyıldız

Joined Dec 26, 2018
4
Thanks Dana for back to me.

I will check G resistance again.
I am using 1X scope probe. Actually I dont know sensitivity of scope. I am using DSG, my teacher is trying to get signals. I just designed the circuit. He didnt understand why we can’t get any signals.

I will get the signals to programming them.

Thanks, Serhat
 
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