How to Build an EMF Tester

Test magnetic field strengths using a voltmeter attached to an EMF detector.

An electromagnetic field (EMF) test meter, or gaussmeter, measures the strength of magnetic fields. EMF test meters are often used for determining the strength of electromagnets or gauging magnetic fields around unshielded electronics. EMF meters have also been used in ghost hunting to search for magnetic field disturbances. You can build your own EMF test meter, with parts from a local electronics or hardware store. You can have your EMF meter built and begin testing magnetic fields in about an hour.

Things You'll Need

• Wiring kit
• 5-volt voltage regulator
• IC breadboard
• 9-volt battery connector
• Hall effect device
• Digital voltmeter
• 9-volt battery
• 2 rubber bands

Instructions

1. Attach the 5-volt voltage regulator to pins 1, 2 and 3 on the breadboard's power bus at the upper left-hand side.

2. Attach the red wire of the 9-volt battery connector to the 5-volt voltage regulator's pin 1.

3. Plug the 9-volt battery connector's black wire into pin 2 of the 5-volt voltage regulator.

4. Connect the Hall effect device to the breadboard's power bus at the upper right-hand side, in line with the 5-volt voltage regulator.

5. Push one end of a green wire from the wiring kit into pin 3 of the 5-volt voltage regulator, push the other end into pin 1 of the Hall device.

6. Attach a black wire from the 5-volt voltage regulator's pin 2, to the Hall device's pin 2.

7. Set the voltmeter to read 20 VDC, then connect the red lead to the Hall device at pin 3 and attach the black lead to the Hall device at pin 2.

8. Snap a 9-volt battery into the battery connector and secure the battery to the breadboard with two rubber bands. The voltmeter should read about 2.5 volts without any magnetic field interference.

9. Test the meter. Set a magnet near the EMF tester and watch meter readings change. Calculate the magnetic field strength by multiplying the difference between the calibrated zero reading (approximately 2.5 volts) and your current reading by 1,000, and divide by the sensitivity of the Hall device. A positive result indicates a north magnetic pole, while a negative result indicates a south pole.

References

• Coolmagnetman: Build Your Own Gaussmeter
• Science Buddies: Measure Your Magnetism
• GhostGadgets.com: EMF Meters Explained