Understanding Linearity, Repeatability, and Phase Lag in Digital Sensors

QL-mini-shm sensor

Digital sensors are the backbone of effective real-time monitoring systems, especially in fields where accuracy and responsiveness are crucial, such as seismic monitoring, structural health assessment, and environmental monitoring. Key performance characteristics—linearity, repeatability, and phase lag—define a sensor’s accuracy, consistency, and responsiveness. Understanding these factors and how they are measured can help ensure the reliability of monitoring systems and the quality of data collected.

Linearity: What It Is and How to Measure It

Definition: Linearity indicates how accurately a sensor’s output follows a straight line relative to the input. Ideally, a sensor should have a direct, proportional relationship between input and output across its full range, meaning that changes in the input yield corresponding, linear changes in the output. However, sensors often deviate from this ideal, impacting their linearity.

Measurement: To measure linearity, test the sensor across its entire measurement range and compare its output to the ideal linear response. Deviations from this line can be quantified as a percentage of the full-scale output. Lower deviation percentages signify higher linearity, making the sensor more reliable for precision measurements.

Importance for Real-Time Monitoring: Linearity ensures the sensor output consistently reflects the actual value of the measured phenomenon, which is crucial in applications like seismic monitoring. Accurate linearity enables sensors to capture ground motion amplitudes precisely, providing essential data for analyzing seismic waves and predicting potential impacts.

Repeatability: What It Is and How to Measure It

Definition: Repeatability is the sensor’s ability to produce the same output under identical conditions over multiple measurements. High repeatability signifies consistent, reliable data collection, which is vital for any monitoring application.

Measurement: To assess repeatability, the sensor is exposed to the same input several times while recording each output. The variations in these measurements are quantified, often using standard deviation. Smaller variations indicate higher repeatability, demonstrating the sensor’s ability to provide consistent results under similar conditions.

Importance for Real-Time Monitoring: High repeatability ensures consistent data, vital in real-time monitoring applications like earthquake early warning systems or structural health monitoring. Reliable, repeatable data builds confidence in the monitoring system’s accuracy, supporting timely and well-informed decision-making.

Phase Lag: What It Is and How to Measure It

Definition: Phase lag, or phase delay, is the time delay between a sensor’s output and the occurrence of the measured event. A low phase lag indicates that the sensor can quickly respond to changes, an essential trait for systems monitoring dynamic or rapidly shifting environments.

Measurement: Phase lag can be measured by applying a known waveform, such as a sinusoidal signal, to the sensor and recording the output’s response time. The phase difference between the input and output is quantified in degrees or time units. A smaller phase lag value indicates a faster response, ensuring the sensor’s output stays in sync with real-time changes.

Importance for Real-Time Monitoring: For critical monitoring applications, phase lag can compromise the reliability of data. In seismic monitoring, a delay in sensor response can affect wave propagation analysis, making low phase lag essential to real-time applications. When phase lag is minimized, data more accurately reflects real-world events, supporting rapid response actions during emergencies.

QuakeLogic’s New QL-MINI and QL-MINI-SHM Sensors

At QuakeLogic, we are excited to introduce our latest additions to our seismic and structural health monitoring (SHM) product line: the QL-MINI and QL-MINI-SHM sensors. These compact, high-performance digital sensors are engineered to offer unmatched precision in real-time monitoring applications, making them ideal for infrastructure, geotechnical, and environmental monitoring.

QL-MINI: Designed for versatility and efficiency, the QL-MINI combines compactness with high accuracy, making it ideal for a range of monitoring applications. With its exceptional linearity and repeatability, the QL-MINI provides consistent data and minimal phase lag, ensuring precise, real-time insights for critical applications.

QL-MINI-SHM: Tailored specifically for structural health monitoring, the QL-MINI-SHM sensor provides advanced data fidelity with ultra-low phase lag and superior repeatability. It’s ideal for monitoring structural integrity, ensuring safety and resilience in buildings, bridges, and other critical infrastructure.

QL-mini-shm sensor

Both QL-MINI and QL-MINI-SHM models are designed to meet the rigorous demands of real-time monitoring, providing the highest levels of accuracy, consistency, and responsiveness. By choosing QuakeLogic’s sensors, you’re investing in state-of-the-art technology that supports proactive maintenance and risk mitigation, offering peace of mind through high-quality, reliable data.

About QuakeLogic

QuakeLogic is a leading provider of advanced seismic monitoring solutions, offering a range of products and services designed to enhance the accuracy and efficiency of seismic data acquisition and analysis. Our innovative technologies and expert support help organizations worldwide to better understand and mitigate the impacts of seismic events.

Contact Information
Email: sales@quakelogic.net
Phone: +1-916-899-0391
WhatsApp: +1-650-353-8627
Website: www.quakelogic.net

For more information about our products and services, please visit our website or contact our sales team. We are here to help you with all your seismic monitoring needs.

Thank you for choosing QuakeLogic. We look forward to assisting you with your seismic monitoring projects.

Shake Table Testing for Nonstructural Components: AC 156 Applications

The AC 156 standard is the go-to method for testing nonstructural components for seismic performance. Nonstructural elements—such as equipment, ceilings, and mechanical systems—are critical for maintaining operational functionality during and after seismic events. The ability to accurately replicate seismic forces through shake table testing ensures that these components perform as intended under real-world earthquake conditions.

The AC 156 standard is widely adopted for evaluating the seismic performance of nonstructural components, such as HVAC systems, lighting fixtures, ceilings, and mechanical equipment. These elements, while not part of the structural frame, are essential for operational continuity during and after seismic events. Accurately replicating seismic forces through shake table testing ensures these components can perform as intended under real-world earthquake conditions.

This blog provides a detailed roadmap covering seismic data access, response spectrum generation, shake table setup, and post-test analysis. The goal is to help professionals meet AC 156 compliance effectively, whether for U.S. or international projects.

1. Importance of SD Values for Nonstructural Testing

SD values represent the short-period design acceleration, evaluated at 0.2 seconds spectral period, and are critical for defining the seismic forces applied to nonstructural components. Accurate SD values ensure the testing reflects site-specific seismic hazards, aligning with AC 156 requirements.

2. Tools for Accessing SD Values in the United States

  • ASCE Hazard Tool: Generate seismic design parameters such as SD for specific U.S. locations by entering project coordinates.
  • Seismic Design Maps: A USGS-powered tool offering detailed seismic hazard information for compliance with building codes.

These tools streamline seismic design, ensuring compliance with AC 156 standards for U.S.-based projects.

3. Finding SD Values for International Projects

Each region has unique seismic hazard models, making it challenging to obtain accurate SD values internationally. Below are useful resources for global projects:

Additionally, QuakeLogic offers custom seismic hazard data for regions such as:

  • Turkey
  • North Africa
  • Central Asia
  • Europe

For tailored seismic data, contact us directly. We can provide SD values, scaled ground motions, and site-specific data.

4. Ground Motion Selection and Filtering for AC 156 Testing

Ground motion selection is a critical step to ensure the seismic conditions simulated on the shake table accurately reflect site-specific hazards.

  • NGA West 2 Database: Access a wide range of unscaled ground motion records. Use filtering tools to select appropriate records based on parameters such as magnitude and fault type.

According to AC 156, both horizontal and vertical seismic forces must be tested separately or simultaneously. The selected motions should meet the Required Response Spectrum (RRS) derived from the building’s location.

5. Ground Motion Scaling and Spectral Matching

Scaling and matching ground motion to the Test Response Spectrum (TRS) is essential for AC 156 compliance. Key techniques include:

  • Time-Domain Matching: Adjusts time history to align with the target spectrum.
  • Frequency-Domain Matching: Alters frequency content to match the RRS.

The process ensures the test simulates real seismic forces and meets performance standards required by ASCE 7-22.

6. Generating a 5% Damped Response Spectrum Using Python

A 5% damped response spectrum is the standard reference for seismic design and testing. We offer a free Python code that generates this spectrum, along with an example for easy implementation. This tool will aid in compliance with AC 156 by ensuring the selected ground motions meet the required spectrum. Please reach us at support@quakelogic.net

7. Shake Table Setup and Instrumentation Overview

AC 156 requires rigorous shake table testing to certify nonstructural components. Below are key elements for setup:

Shake Tables:

  • Electromechanical Tables: For small components.
  • Servo-Hydraulic Tables: For larger equipment.
  • Portable Bi-Axial Tables: For field applications or lab testing.

Sensors and Instrumentation:

  • Accelerometers measure acceleration during shaking.
  • Displacement Sensors track movement.
  • Strain Gauges monitor internal stress.

The Test Response Spectrum (TRS) measures the actual response of components under seismic forces. TRS must envelop the RRS to ensure the test simulates seismic events accurately.

8. Post-Test Analysis and Certification

After testing, post-test inspections verify the operational and physical integrity of components. The component must maintain:

  • Structural Integrity: Limited yielding allowed, but no significant damage.
  • Operational Integrity: Critical components (Ip = 1.5) must function post-test.
  • Anchorage Compliance: All mounting systems must remain intact during testing.

Detailed reports documenting setup, results, and performance are essential for certification. Compliance with ASCE 7-22 and FEMA 461 ensures regulatory approval and safety in high-risk seismic zones.

9. Industry Applications of AC 156

AC 156 is essential for sectors where nonstructural components must remain operational during seismic events, including:

  • Healthcare: Hospitals require seismic compliance for life-sustaining equipment.
  • Telecommunications: Ensures data centers remain operational post-earthquake.
  • Energy and Utilities: Critical systems must withstand seismic forces for safety.
  • Nuclear Power: Adheres to IEEE Standard 344 for seismic qualification.

Shake table testing provides confidence that nonstructural components will perform reliably under seismic conditions, minimizing downtime and enhancing safety.

10. Selecting the Right Shake Table for Your Project

At QuakeLogic, we offer a variety of shake tables designed to meet AC 156 standards:

Please share your shake table specifications, and we will prepare a custom offer. Reach us at sales@quakelogic.net

Conclusion

Shake table testing under AC 156 is critical for certifying the seismic performance of nonstructural components. By selecting appropriate ground motions, scaling them accurately, and using advanced instrumentation, you can ensure compliance and operational integrity.

With tools like the ASCE Hazard Tool, Global Seismic Hazard Map, and NGA West 2 Database, we help you meet AC 156 requirements effectively for both domestic and international projects.

As always, “Seeing is Believing”—reach out to us for shake table demonstrations or solutions tailored to your needs.

SIS-1 Infrasound Sensor: Cutting-Edge Infrasound Detection for Civil and Military Applications

The SIS-1 Infrasound Sensor, developed in collaboration with CEA, is a high-performance, low-power sensor designed for a wide range of civil and military applications. This portable sensor provides exceptional infrasound detection capabilities, enabling rapid deployment for diverse monitoring needs.

Key Features and Applications

1. Civil and Military Security Solutions
The SIS-1 sensor is versatile in detecting infrasound events across a broad range of applications.

  • Military Applications: Nuclear explosions, missile launches, and drone detection are among the sensor’s critical uses, enhancing defense and security.
  • Civil Applications: SIS-1 also plays a vital role in natural disaster monitoring, including earthquake and tsunami detection, weather-related phenomena like tornadoes and avalanches, and emerging environmental emissions tracking, such as those from wind farms.

2. Exceptional Detection Range
This sensor is designed to detect infrasound events from frequencies as low as 1 Hz, making it a premier solution in the infrasound sensor market. The SIS-1 supports chainable deployment for extensive coverage and offers easy installation and maintenance, making it ideal for both temporary and permanent installations.

3. Innovative System Composition
The portable SIS-1 system includes:

  • Infrasound Sensor: Core to detecting and monitoring infrasound events.
  • Digitizer and Data Transmission: Ensures accurate data capture and real-time transmission.
  • Power Supply and GPS: Self-contained for autonomous deployment and location tracking.
  • Optional Components: Wind noise reduction systems (WNRS) and a weather station enhance accuracy in varied environmental conditions, maintaining the sensor’s reliability.

Advanced Metrology and Testing Standards

Seismo Wave’s metrology standards underscore the sensor’s quality:

  • Dynamic Infrasound Generator: Calibrates and tests the sensor’s infrasound response.
  • Metrology Room: Offers precise control over temperature, ground vibration, and meteorological conditions, ensuring accuracy.
  • Active Vibration Isolation Tables: Assure minimal interference, critical for accurate low-frequency measurements.

Technical Specifications

The SIS-1 sensor features impressive self-noise characteristics and maintains amplitude and phase accuracy, essential for detecting even the faintest infrasound signals. These specifications make it a top choice for applications requiring precision and reliability.

Whether used for civil applications like earthquake detection or military applications for blast and drone detection, the SIS-1 infrasound sensor stands out for its flexibility, chainable configuration, and adaptability to both routine and high-stakes monitoring scenarios. The SIS-1 is a complete, portable solution for organizations that prioritize early event detection and broad monitoring coverage.

Additional Offerings

At QuakeLogic, we go beyond providing just the SIS-1 infrasound sensor. We also offer:

  • Analog Dataloggers: For accurate and reliable data collection from infrasound sensors.
  • Real-Time Monitoring Software – PulsePro: To enable continuous monitoring and immediate analysis of infrasound data, ensuring quick responses to any detected anomalies.

Special Introductory Offer

We are offering the SIS-1 at a special introductory price, exclusively for our valued customers. We firmly believe that the SIS-1 is poised to meet and surpass your sound detection needs. Take advantage of this limited-time offer and secure your Infrasound Sensor SIS-1 today. Click HERE for the product page.

About QuakeLogic

QuakeLogic is a leading provider of advanced seismic monitoring solutions, offering a range of products and services designed to enhance the accuracy and efficiency of seismic data acquisition and analysis. Our innovative technologies and expert support help organizations worldwide to better understand and mitigate the impacts of seismic events.

Contact Information

Email: sales@quakelogic.net
Phone: +1-916-899-0391
WhatsApp: +1-650-353-8627
Website: www.quakelogic.net

For more information about our products and services, please visit our website at https://quakelogic.net or contact our sales team. We are here to help you with all your seismic monitoring needs.

Thank you for considering our latest product. The SIS-1 infrasound sensor, along with our comprehensive range of analog dataloggers and real-time monitoring software, is designed to provide you with the precision, speed, and reliability required for advanced sound detection. We stand ready to answer any queries or assist you in any way we can.