Electrical Interference in Biomedical Measurements: Analysis and Detection — An Exploratory Laboratory Module

This resource presents an exploratory laboratory module on electrical interference in biomedical measurements, designed for undergraduate courses in biomedical instrumentation, electrical engineering, and related fields.

The lab introduces students to the analysis, characterization, and mitigation of electromagnetic interference (EMI) in low-amplitude biopotential measurements. Students investigate common sources of interference, including 60 Hz power-line coupling, radio-frequency signals, and environmental electromagnetic fields, through hands-on experiments using oscilloscopes, differential amplifiers, and conductive subjects.

A key feature of the module is that students directly observe how electromagnetic fields couple into both the measurement system and the human body, demonstrating capacitive pickup and the role of the body as part of the measurement circuit. The lab emphasizes:

• Identification of interference mechanisms (common-mode and differential-mode)
• Effects of measurement impedance and loading
• Modeling of interference using Thevenin equivalent circuits
• Use of shielding and differential amplification for interference reduction
• Identification of frequency content, including power-line interference and radio-frequency signals
• Recognition and analysis of aliasing effects in undersampled high-frequency signals

The module explicitly connects experimental observations to real-world engineering requirements. Students examine how interference affects measurement reliability and how such effects relate to electromagnetic compatibility (EMC) and safety requirements defined by standards such as IEC 60601-1-2 for medical electrical equipment.

Unlike traditional step-by-step laboratories, this module adopts an open-ended, inquiry-based approach. Students must actively select measurement settings, configure experiments, and interpret results under conditions where signals may be ambiguous, distorted, or misleading. Rather than focusing on obtaining a single “correct” result, the lab emphasizes understanding how measurements change with environment, configuration, and instrumentation.

A central objective of the lab is to develop students’ ability to evaluate measurements under uncertainty. Students encounter signals that appear structured and valid but may not represent the underlying physical phenomenon due to interference, coupling, or sampling effects. This requires them to question results, investigate anomalies, and justify interpretations using physical reasoning.

The module also explicitly integrates engineering ethics within technical practice. Students must recognize how routine measurement decisions—such as ignoring interference, misinterpreting signals, relying on automated instrumentation settings, or failing to investigate unexpected behavior—can lead to incorrect conclusions and unsafe outcomes in biomedical systems. The lab emphasizes intellectual honesty, disciplined analysis, and responsibility under pressure, particularly when results are unclear or inconvenient.

The laboratory is designed to support ABET student outcomes, particularly:

• Application of engineering principles to analyze and interpret data
• Ability to design and conduct experiments under realistic constraints
• Identification and characterization of system behavior under uncertainty
• Recognition of professional and ethical responsibilities in engineering practice
• Development of critical thinking and engineering judgment

The module has been implemented in an upper-level biomedical instrumentation course and is designed to be adaptable across institutions. It provides a complete instructional package, including:

• Lab handout with structured experimental activities
• Guidance for exploratory measurement and data interpretation
• Integrated ethics and reflection prompts
• Assessment-aligned data recording templates

This work contributes to engineering education by demonstrating how technical laboratory instruction can simultaneously develop experimental skill, signal analysis capability, and responsible engineering practice through standard instrumentation topics.