John Errington's Experiments with an Arduino

Voltage measurement with the Arduino microcontroller.

Using the Arduino's ADC to measure voltage

The pages in this section explain how to make a wide range of measurements, and how to interpret your results.

Simple circuits

Start here. Basics of measuring voltages with an arduino using an ADC input pin

Internal and external reference voltages

Choose the right reference! Assuming your reference voltage is 5V (or 3.3V ) Vcc, even assuming the INTERNAL reference is accurate can give incorrect results.

Measure the right voltage

If you have the wrong connections it can produce unexpected readings. Read about the need for a "star point" here.

Measuring the supply voltage

Simple ways to check your supply voltage

How the ADC works

And how to interpret the results as a voltage.

Better measurements from the ADC

How to use your ADC to get more precise or more accurate readings

High impedance measurements

Precautions you need to take if reading from a high resistance source.

Calibration

How to get a more accurate reading of voltage

Millivoltmeter

Measuring very low voltages using an Instrumentation Amplifier

Using Operational amplifiers (Op-Amps)

How a simple electrical component can help you make a wider range of measurements

Logging voltage measurements

Putting it all together: Arduino Mega, Ethernet shield with SD card, and a simple amplifier
to log voltage measurements in the range 0-2.5V or 0-25V and display results to a web page.

Measuring device characteristics

Another example showing the use of op amps to make measuremnts with the ADC