Electronics workshop: electromagnetic field meter

Electronics workshop: electromagnetic field meter


In Todoelectronica we encourage training and learning with electronics course.

New project for electronic learning by doing.

We propose a new electronic project . All electrical and electronic equipment we use in our daily emit energy, usually in the field of far infrared (heat) and the radio field. But to what extent these emissions occur? To find out we suggest making your own electromagnetic field meter . Let’s do it!

While the exact measurement of these fields (intensity, frequency, scope …) is complicated – and more – even analysis, the realization of a meter is relatively simple , as long as it is used only as relative value.

Ie with our meter and simple comparison can detect what our home appliances emit more electromagnetic radiation and what is its scope.

The circuit is very simple, suitable for all levels.

Electronic scheme meter electromagnetic field.

We can detect that our monitor emits more radiation than the electronic watch our bedside table, though the latter is more dangerous because it is closer to us during sleep, and longer (theoretically about 8 hours).

This assembly will allow us to control and move away in a rational manner of those devices that emit excessive radiation.

Electronic components are easy to find.

List of components for this project.


In Figure 1 will find the electronic meter this simple scheme. The operation is as follows :

A small coil 1 mH capture any field induction electromagnetic origin and creates a small voltage at its ends.

This voltage is applied through the 100nF capacitor to the input of operational amplifier that handles about 2000 times increase.

The resistors 10K and 10 uF capacitor , forming the decoupling bias network and the amplifier.

The resistance of 2.2M ohms is the loop gain in this circuit is 2000. The 150 pF capacitor , prevents the oscillation of the amplifier; this component is very important because without it, the circuit starts to oscillate and does not work.

The amplified signal at the output is decoupled by the capacitor 220uF . This signal can be heard in a small speaker 32 ohms (hulls).

To limit the sound and that this does not become annoying, it has been included limiting resistor of 10 ohms .

The NPN transistor and its associated resistors form a common emitter amplifier. This circuit amplifies the current and voltage signal, then apply it to the meter needle type (galvanometer) .

The two silicon diodes form the rectifier charge to eliminate the negative half cycles of the amplified signal.

The capacitor 220 uF closes the circuit and acts as an integrator.

Feed for this circuit only requires a 9V battery .


It is important to double check the welds and connections.


For mounting the circuit only needed components listed . Welding one need welder 30w , tin of 1 mm and a side cutter to remove the pins once welded.

Once assembled plate is advisable to check to prevent failure by inverted or wrong components wirings. The circuit does not require any adjustment, if all is well should work first.

For the measurement of electromagnetic fields, only coil 1 mH must bring the apparatus to measure , for example a monitor.

Depending on the emission of the apparatus, the needle will move more or less, which by comparison will give us an idea of ​​what devices emit more than they do and how far.

With a few additional circuit components can also detect radiation in the field of microwaves (2450 MHz), and it would be useful for the measurement and maintenance of microwave ovens, do you dare to perfect this project?

We encourage you to make this show, and if you want to learn more and do more montages, we propose to expand knowledge in electronics course or mounting kits Todoelectronica. And practicing!

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