Gauss meters are expensive devices and are typically not within reach of the average electronics hobbyist. Presented here is the simplistic design of an inexpensive gauss meter that can teach you about the strength of magnets. This construct is based on the easily-available SS49E Hall effect sensor from Linear Technology. This is an affordable DIY project presented as a design idea for further refinement and optimizing of the basic concept by way of experiment.
The SS49E Linear Hall effect sensor is a versatile device that’s operated by the magnetic field from a permanent magnet or an electromagnet. The linear sourcing output voltage is set by the supply voltage and varies in proportion to the strength of the magnetic field. The “UA” package that’s easiest to work with is called the Single Inline Package (SIP), which allows you to easily plug into a breadboard or solder into a veroboard.
The front end of the gauss meter is designed as a small module, with the Halleffect sensor SS49E (IC1) and a Linear Voltage regulator chip — LM78L05 (IC2). The 3-pin header (H1) allows you to easily link the module to any compatible circuitry. Refer to the circuit diagram of the module, and follow my artwork example (this model must be scaled down) to make your own circuit board.
This module’s supply voltage range is relatively wide (thanks to the onboard voltage regulator). The unit is particularly suitable for operation from a 9 V alkaline battery connected between the VCC and GND points of the header, H1. Note that the quiescent output voltage, available across OUT and GND points of H1, is somewhere around ½ VCC (~2.5 V). This idle voltage will increase if a magnet’s south pole is within the close proximity of the “labelled-side” of the Halleffect sensor (the output will decrease in case of a north pole). You can also use this module as a magnet pole finder.
When it comes to the construction of an Arduino gauss meter, follow the sketch included below, which displays the effect of north (N) and south (S) magnetic fields close to the sensor module in the serial monitor. The hardware setup is very simple; connect the OUT and GND points of the header H1 to A0 and to the GND of the Arduino board. Next, power up the module using a 9 V battery, and plug the Arduino hardware into a USB port on your computer. The 10 K resistor (R1) in the module is not necessary with this specific application.
Postscript: According to datasheets, the SS49E sensor outputs voltage in 1 to 4 V range. So with a 5V as the analog reference: 5V = 1024, 1V = 205, and 4V = 819. For better results, check the exact VCC voltage of the Arduino and tweak this data using theoretical and empirical methods.