Go Down

Topic: Adjusting sensor voltage and ADC (Read 817 times) previous topic - next topic

TomS

Hello Arduino forum!

I've got a sensor that gives me a small voltage between 2 and 10 millivolts.
I'd like to use the Arduino to sample this sensor.

Since the voltage provided is very small, I was wondering what would be the better approach, amplifying the voltage (how?) or decreasing the reference voltage of the ADC?

Thanks a lot for any advice! :)
Tom

MarkT

The ADC cannot operate with a reference voltage below about 1V, BTW - the built-in analog reference is 1.1V, but that's still not going to help you much.

You need to amplify the signal.  This is a classic case of needing an instrumentation amplifier since your signal is so small.  Look at the specs for the MAX4208 for example for a 5V single-rail device with rail-to-rail capability. http://www.maxim-ic.com/datasheet/index.mvp/id/4925 - other manufacturers make instrumentation opamps too!

Alternatively a single-op-amp circuit can be used but won't be as accurate due to time and temperature drift.  Depends on your precision requirements (you'll definitely need a 'precision low voltage' opamp that works down to the negative rail.  If your sensor has a high output impedance the instrumentation amp is the best route I think.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

TomS

Hello Mark, thanks for your advice!

I had an LM358 here and tried the non inverting dc gain application from the datasheet and it is already a nice improvement. Don't know yet if it will be precise enough, so I will keep your advice on the MAX4208 and instrumentation amplifier in mind, thanks a lot!

Have a great day!
Tom

Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy