Hello all!

I have been working on a project where I need to take a 100mv - 250mv signal and amplify that to something around 5v to feed into my Arduino. I have had great difficulty with this, as the frequency is rather low (~60 to 500 hz). Is there anything specific I should be taking into account when designing this? Also, I have just started back with electronics after some time away from it, so any help would be greatly appreciated!

Thank you,

Chris C.

 

What circuits have you tried (schematic please), and what seemed wrong with its peeformamce?

What is the nature of the incoming signal (AC coupled or DC coupled, what frequencies and waveshape?)

Do you intend to connect this to am analog-to-digital converted? If not what will you do with the amplified signal?

 

An opamp will handle that easily.

Bob

 

Is the AC signal +/- around ground?
If so you would need to AC couple and offset it to fit within the 0-5V input of the Arduino.
As Bob suggested, an op amp can do that.

 

If an op amp is configured as a very basic unity gain or voltage follower and input is 100mV
the output should be 100mV ideally. The input might be 103mV so when the meter agrees with your follower (then add gain).
If you have any trouble with possibly your meter reads 249mV instead of 250mV

Now the focus is on an op amp configuration that will give you precision gain, you will trim set and output will reflects the level shift.

This can be done with a transistor however, much of the what is inside the op amp is very helpful in accurately
performing the operation of amplifier. The op amp is not perfect. The dilemma between real and ideal does have some remedy.
After the fluctuation is minimized averaging can improve the accuracy. somebodies video on ltc2400. If it matches my precision reference
then Avg is good enough. The time it takes for me to warm up the plastic is about 30 minets.

Can you filter and make the Avg samples better?
The question about what to take into account in designing can be seen in an evaluation board that is doing all that.
There is plenty of specifics in the entire arrangement not withstanding are the errors coming from outside the desired range.
The amplifier can be frequency selective. Low audio range between 50 - 500 Hz.
What about above 500 Hz, Would you like a low pass filter ? How about below 50 Hz, would you like a high pass ?
When it's filtering right possibly your samples will take on a bell shaped curve, possibly the Avg you are aiming for less a few digits.
There are times that I need to wait 10 or 20 seconds (I don't mind waiting) because all I want is a number 1.288624 now I have what I need to complete what I am doing specifically. I prefer no snap crackle pop or hissing.