50/60 Hz Notch Filtering: Eliminating Power-Line Interference at the Sensor Level Power Line Interference

Maintaining low-noise pressure measurements in electrically noisy environments

Power-Line Interference Remains a Silent Performance Killer

Despite major advances in digital signal processing and system integration, power-line interference at 50 Hz or 60 Hz remains a persistent source of measurement corruption in electromechanical systems.

Depending on the geographic region, AC mains operate at either 50 Hz or 60 Hz. This fundamental frequency and its harmonics couple into sensitive electronics through:

• Power supplies
• Ground loops
• Motor drives
• HVAC equipment
• Industrial machinery
• Nearby electrical infrastructure

In many applications, this interference is masked by broader system noise. However, in high-resolution pressure-sensing systems, especially those operating at very low differential pressures, power-line energy can become dominant relative to the signal of interest.

The result:

• Degraded signal-to-noise ratio (SNR)
• Spurious pressure fluctuations
• Reduced measurement resolution
• Instability in downstream control loops

For applications such as airflow measurement, HVAC control, gas analysis, and medical respiratory devices, even small AC-induced artifacts can significantly affect system performance.

Why External Notch Filtering Is No Longer Optimal

Traditionally, engineers suppress 50/60 Hz interference by implementing external analog or digital notch filters at the system level. Although effective, this approach has several drawbacks:

• Additional analog components and PCB area
• Increased design and validation effort
• Sensitivity to component tolerances and temperature drift
• Filtering occurs after interference has already entered the signal chain

In modern systems where designers optimize for size, power, reliability, and time-to-market, external filtering is an unnecessary complexity.

NimbleSense^TM Integrated 50Hz/60Hz Notch Filter

Superior Sensor Technology addresses this challenge by embedding a digital notch filter directly within the NimbleSense™ System-in-a-Sensor architecture. Rather than treating power-line noise as a system-level problem, NimbleSense eliminates it at the sensor module, preventing interference from propagating downstream.

Key Architectural Advantages

• Notch filtering is applied immediately after signal acquisition
• AC interference is removed before it affects measurement accuracy or control logic
• No external filter design is required
• Sensor-level filtering preserves the inherently low noise floor of Superior’s MEMS technology

Because the notch filter is tightly coupled to the sensor’s internal signal-processing path, it operates deterministically, without the variability of discrete analog implementations.

Designed for Low-Noise, High-Resolution Pressure Systems

Superior’s differential pressure sensors are engineered with extremely low intrinsic noise. Ironically, this makes them more susceptible to environmental interference because 50/60 Hz artifacts become visible once the sensor’s noise floor is low enough.

The integrated notch filter allows designers to retain the benefits of ultra-low-noise sensing while eliminating AC grid contamination that would otherwise obscure low-pressure measurements. This capability is particularly valuable in:

• HVAC airflow and filter monitoring
• Industrial flow control
• Environmental sensing
• Medical respiratory equipment
• Gas sampling and analysis systems

In these applications, removing power-line interference improves both static accuracy and dynamic response.

System-Level Benefits

By integrating 50/60 Hz rejection directly into the pressure sensor, NimbleSense delivers:

Improved Measurement Integrity

• Higher effective SNR
• Cleaner low-pressure readings
• Reduced spurious oscillations

Simplified Design

• No external notch circuitry
• Fewer BOM components
• Reduced PCB complexity

Faster Development

• Eliminates filter design and tuning
• Shortens validation cycles

Lower Total System Cost

• Fewer parts
• Higher long-term reliability

Availability

The NimbleSense integrated 50/60 Hz notch filter is available on Superior Sensor Technology’s HVAC and industrial pressure-sensing platforms, including:

• HV Series
• ND Series
• Custom products

The notch filter can also be used in combination with NimbleSense Advanced Digital Filtering for applications that require aggressive noise suppression in challenging electrical environments.

Conclusion

High-performance pressure sensing demands more than raw accuracy; it requires intelligent noise management at the source. By embedding 50/60 Hz notch filtering directly in the sensor subsystem, NimbleSense™ prevents power-line interference from entering the signal chain. The result is cleaner data, simpler designs, and more robust systems without the overhead of external filtering.

If you have an application in a challenging noise environment that can benefit from a lower noise floor, please contact us to discuss how best to integrate the NimbleSense 50Hz/60Hz notch filter with our advanced digital filtering to achieve maximum overall system performance.