# Arduino Forum

## Using Arduino => General Electronics => Topic started by: adityak on Oct 14, 2016, 05:40 pm

Title: Amplifying Low Voltage AC signal
Post by: adityak on Oct 14, 2016, 05:40 pm
Hello!!

I have a vague idea how to solve this problem and I am looking for specific suggestions as I am from mechanical background.

I have a data acquisition system that can take minimum 100mV ac voltage. But my sensor generates a low voltage ac signal with maximum of 30mV peak to peak. So I am looking to amplify the signal before connecting my sensor to the data acquisition system.

In short, I am looking for suggestions or solutions on how to amplify a 0-30mV peak to peak ac signal to a minimum 100mV ac signal without altering the frequency.

Thank you

Regards
Title: Re: Amplifying Low Voltage AC signal
Post by: CrossRoads on Oct 14, 2016, 06:17 pm
You need an Op Amp.
Do you need it Arduino compatible (0-5V range),
http://masteringelectronicsdesign.com/the-transfer-function-of-the-summing-amplifier-with-n-input-signals/ (http://masteringelectronicsdesign.com/the-transfer-function-of-the-summing-amplifier-with-n-input-signals/)
- Add some gain and DC offset to make it 2.5V +/- your signal. Ex your .03V signal with a gain of 50 to make it +/- 1.5V, and add in DC of 0.05V on the 2nd input to make the output 2.5V +/- 1.5V.

Or do you just need it amplified (to -100mV to +100mV or more)? Same circuit can be used, just leave off the V2 input.
Dual power supply needed to allow +/- input & output.

Or use capacitive coupling with a single supply rail to rail output, see Figure 12 here:
Title: Re: Amplifying Low Voltage AC signal
Post by: MarkT on Oct 14, 2016, 07:07 pm
Hello!!

I have a vague idea how to solve this problem and I am looking for specific suggestions as I am from mechanical background.

I have a data acquisition system that can take minimum 100mV ac voltage. But my sensor generates a low voltage ac signal with maximum of 30mV peak to peak. So I am looking to amplify the signal before connecting my sensor to the data acquisition system.

In short, I am looking for suggestions or solutions on how to amplify a 0-30mV peak to peak ac signal to a minimum 100mV ac signal without altering the frequency.
Do you mean -15mV to +15mV peak-to-peak or 0 to +30mV peak-to-peak?

What is the bandwidth of the signal?  What is the sample-rate of your data-acquisition system?
Perhaps you could tell us exactly which sensor this is?  And which data-acquisition system.

Also before replying check that this isn't an xy-problem: http://xyproblem.info/ (http://xyproblem.info/)
Title: Re: Amplifying Low Voltage AC signal
Post by: adityak on Oct 14, 2016, 07:25 pm
Thanks for the replies guys. I appreciate your time.

Hey sorry for the confusion, it is -30 mv to +30 mV peak to peak.

The DAQ is NI SCXI 1102. Sampling rate is 300Hz.

Sensor is Omega FTB 1411 Flowmeter. It's a magnetic pick up sensor, which generates ac voltage.

Thank you.