The field of quantum sensing has shown rapid advancement in recent years. These advances have focused on making quantum sensors, which previously required laboratory environments and expensive bulky equipment, more portable and cost-effective. These developments are largely due to the use of nitrogen-vacancy (NV) centers in diamond. NV center diamond is suitable because its quantum mechanical properties can be observed over a wide range of temperatures and do not require strictly controlled conditions such as environmental shielding. These characteristics make NV centers promising candidates for sensing applications, such as defense-related technologies. Potential applications include magnetometry for navigation and radio-frequency sensing for signal interception, motivating the project conducted at the Swedish Defence Research Agency (FOI). This thesis presents and evaluates a low-cost and portable design of an NV center based magnetometer to determine the feasibility of such designs. The results demonstrate that the sensor is capable of detecting the underlying quantum phenomena in a diamond containing NV centers, yielding an optically detected magnetic resonance (ODMR) signal. Furthermore, the sensor responds to changes in magnetic fields. However, several design challenges remain before achieving high-accuracy sensing performance.