Vol. DIY Electronics Projects
Chapter 4 AC Circuit Projects

AC Lab - Sensing AC Electric Fields

In this hands-on AC electronics experiment, you will sense AC electric fields using the sensitive voltage detector and learn about capacitive coupling, EMI, and shielding techniques.

Project Overview

Low-level electric fields are all around us. These electric fields often interfere with other electronic systems through what is called electromagnetic interference (EMI). As illustrated in Figure 1, a simple wire may be used to sense AC electric fields using the audio detector circuit, explained in an earlier project chapter, to detect AC voltages in the audio frequencies. 


The schematic diagram for sensing AC electric fields.

Figure 1. The schematic diagram for sensing AC electric fields.


Parts and Materials

  • Audio detector with headphones


Learning Objectives

  • To determine the effects of electrostatic (capacitive) coupling.
  • Electrostatic shielding techniques.



Step 1: Ground one lead of the detector to a metal object in contact with the earth (dirt); most any water pipe or faucet in a house will suffice. Take the other lead and hold it close to an electrical appliance or lamp fixture.

WARNING: Do NOT try to make contact with the appliance or with any conductors within! Any AC electric fields produced by the appliance will be heard in the headphones as a buzzing tone.


Simplified illustration of the sensor system to detect AC electric fields.

Figure 2. Simplified illustration of the sensor system to detect AC electric fields.


Step 2: Try holding the wire in different positions next to a good, strong source of electric fields.

Step 3: Try using a piece of aluminum foil clipped to the wire’s end to maximize capacitance (and, therefore, its ability to intercept an electric field).

Step 4: Try using different types of material (paper, fabric, aluminum foil) to shield the wire from an electric field source. What material(s) works best? How does this compare with the AC magnetic field experiment?

As with magnetic fields, there is controversy about whether or not stray electric fields like these pose any health hazard to the human body.


Related Content

Learn more about the fundamentals behind this project in the resources below.





Published under the terms and conditions of the Design Science License