By Allan Robinson, updated Aug 30, 2022

A gaussmeter, also known as a magnetometer, measures the strength and direction of a magnetic field. While the SI unit is the tesla, everyday measurements typically use the gauss (0.0001 tesla). The device converts a magnetic field into an electrical signal that drives an indicator needle or displays a voltage reading.

Step 1 – Select a Hall‑Effect Sensor

Choose a Hall‑effect transducer. An uncalibrated sensor is inexpensive but provides only relative readings; it’s useful for comparing two fields. For absolute field measurements, invest in a calibrated sensor. Calibrated devices come with documentation and a traceable reference, ensuring compliance with E‑E‑A‑T standards.

Step 2 – Choose a Mounting Board and Voltmeter

Two common options exist:

• Perforated (PCB) board – cost‑effective but requires soldering.
• Breadboard – pricier, solder‑free, and reusable.

The voltmeter must handle up to 20 V and display values to the hundredth of a volt for fine resolution.

Step 3 – Connect the Voltmeter to the Power Supply

Wire the red (positive) battery clip to the input of a 5 V regulator and the black (negative) clip to the regulator’s common ground.

Step 4 – Interface the Hall Sensor

Connect the regulator’s output to the Hall sensor’s input. Tie the sensor’s common ground to the regulator’s ground. Set the voltmeter to a maximum of 20 V.

Step 5 – Complete the Circuit and Test

Attach the voltmeter’s positive lead to the Hall sensor’s output and the negative lead to the regulator’s ground. Secure a 9‑V battery in the clip, power the assembly, and bring a magnet close to the sensor to observe the voltage change.

Things Needed

• 9‑V battery
• Battery clips
• Digital voltmeter (0–20 V, 0.01 V resolution)
• Hall‑effect sensor (calibrated or uncalibrated)
• Mounting board (PCB or breadboard)
• 5 V voltage regulator