Magnetic fields play a crucial role in modern science and technology - yet precise and accessible tools for their measurement remain limited, especially for small laboratories, educators, or independent researchers. This paper introduces a novel, open-source magnetic field measurement system based on three-axis sensors for monitoring both direct and extremely low frequency magnetic fields. The device features a modular hardware design centered around a custom PCB, enabling flexible analog filtering, Bluetooth data transmission, and offline LCD visualization. By combining the MC858 and MPU9250 sensors with precise analog signal conditioning and a 12-bit ADC, the system ensures reliable detection of magnetic fields including the 50 Hz mains frequency and its harmonics. To verify the functionality of the device, experimental measurements were conducted inside a Faraday cage using a common hair dryer placed at distances of 1 cm and 3 cm from the sensors as a source of electromagnetic field. Frequency analysis confirmed reliable detection of the dominant 50 Hz component and its harmonics, as well as the system’s ability to distinguish changes in field intensity based on distance and operating state of the source device.

Commercial pacemaker (PCM) analyzers are often expensive, proprietary, and difficult to adapt for experimental biomedical research and educational applications. This work presents a low-cost modular platform for the generation, acquisition, and real-time analysis of pacemaker-related electrical signals. The proposed system consists of two independent printed circuit boards: a digital-to-analog (DAC) board for generation of controlled atrial and ventricular test waveforms and an analog-to-digital (ADC) board for multi-channel signal acquisition and wireless data transmission. A dedicated Qt-based desktop application provides real-time visualization and storage of the acquired signals. Experimental validation was performed using a single commercial dual-chamber pacemaker operating in the DDD mode. For the DAC subsystem, pacing-rate errors remained below 2% over the investigated range of 60–120 BPM, with coefficients of determination exceeding 0.99998 between programmed and measured pacing rates. The ADC subsystem demonstrated relative amplitude errors ranging from 0.96% to 7.19% over the investigated input range of −1000 to −2000 mV. For a programmed atrioventricular delay of 200 ms, the ADC-derived delay was 205.53 ± 1.24 ms, corresponding to a relative error of 2.77%. Combined DAC–ADC operation further demonstrated generation of a controlled atrial test signal, pacemaker sensing and ventricular pacing response, and subsequent acquisition of the response by the ADC subsystem. The developed platform provides a configurable and modular experimental environment in which signal generation and acquisition can be operated either independently or jointly. Its low implementation cost, wireless data transmission, and customizable hardware and software architecture make it suitable for laboratory research, education, and prototype development involving cardiac pacing systems.