# Problem measuring and acquiring a continuous voltage

Hi, im relatively new using arduino and i need to adquire a continuos signal using analog pin.

Im using arduino and simulink(matlab) with the arduino support package for representing the signal. The problem is that, when i measure the output of my circuit with an osciloscope, i perfectly see the continuous voltage, but when I acquire it with arduino and see it in matlab, I have a kind sinus (added pictured). I dont know if its a problem of sample time (i can choose a sample time in matalb for acquiring the signal) or other stuff. I would be very grateful if you help me.

(if this not the correct place for asking this, please notify me and i’ll change it).

You haven't posted any code, so it is impossible to determine what is wrong.

You need to consider just HOW the Arduino tells the PC what the voltage is. How long does it take to convert the value returned by analogRead() to the form that is sent to the PC? How often can values be sent to the PC?

Continuous Signal --

Is it a slowly varying DC?
Is it a half sine wave (positive part)?
Is it a sine wave (full cycle)?

The Arduino (NANO, UNO, MEGA, and DUE) contains ADC which can convert (analog-to-digital) only uni-polar signal. If you are converting sine wave, you need to think about bipolar ADC like ADS7805 (16-bit).

OR

You can shift the negative part of the signal to the positive region by adding DC offset and later on subtraction in the software (unnecessary complicated job when you can use a bi-polar ADC?)