Measuring Electromagnetic Fields With Just an Arduino and a Piece of Wire
Electromagnetic interference problems can be a real headache to debug. If you need to prove what causes your WiFi to slow down or your digital TV signal to drop; then the ability to measure electromagnetic fields (EMF) can be a big help. Professional equipment is often very expensive; but building an EMF detector yourself is not even that difficult; just take a look at Arduino expert Mirko Pavleski’s convenient hand-held electromagnetic field detector.
The basic idea is quite simple; connect an antenna directly to an Arduino’s analog input and visualize the signal that it measures. Because the input of an ADC is high impedance; it is very sensitive to any stray currents that are picked up by the antenna. So sensitive in fact; that a resistor of a few mega-Ohms to ground is required to keep the sensor from triggering on any random kind of noise. Mirko made that resistance adjustable with a few knobs and switches so that the detector can be used in both quiet and noisy environments.
Making the whole device work reliably was an interesting exercise in electromagnetic engineering; in the first few iterations; the detector would trigger off its own LEDs and buzzer; trapping itself in a never-ending loop. Mirko solved this by encasing the Arduino inside a closed, grounded metal box with only the required wires sticking out. The antenna’s design was largely based on trial-and-error; the current setup with a 7 cm x 3 cm piece of aluminium sheet seemed to work well.
