This is a simple device capable of detecting very weak electromagnetic fields. The relative field intensity is displayed on the LCD display and at the same time are given a buzzer sound signalization and LED light signalization. In this case the sensor is a plain copper wire, with a 1.5mm diameter, but you can use any piece of wire or metal tile. Sensitivity can be adjusted via code, and also by changing the value of the resistor connected between A0 and grounding. With the help of a switch, one of the two values of the resistor is selected, and thus the degree of sensitivity of the device. So we can easily calibrate it, by comparing it to a recalibrated industrial device.
As can be seen below the circuit is very simple and consists of Arduino Nano microcontroller and several external components.
The code is a combination of two parts (Arduino based VU meter by KTAudio for LCD display part, and Aaron ALAI EMF Detector for sensor part) and also modifications to certain parts of it for the purpose of greater stability of the whole device. You can download it on link given below.
As you can see in the video, this device can easily detect electromagnetic fields generated by power cables that are only under voltage and not connected to a consumer. For example, an electromagnetic field from an old CRT monitor can be detected at a distance of 3m and more.
The detector is mounted in a convenient housing and is powered by a 9V battery.