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.

MOTIONMASTER-6 Stewart Platform for Advanced 6-DOF Testing Across Industries

The Stewart Platform, commonly known as a hexapod, has revolutionized motion simulation with its six degrees of freedom (6-DOF) capabilities. Originally developed as a parallel manipulator, the Stewart Platform enables high-precision movement across three translational and three rotational axes, making it the ideal choice for advanced shake table applications across multiple industries.

In this post, we’ll delve into how Stewart Platforms, specifically QuakeLogic’s MOTIONMASTER-6, enable powerful 6-DOF motion simulations, advancing research and testing in fields from earthquake engineering to aerospace, automotive, and beyond.

What is a Stewart Platform?

A Stewart Platform is a robotic manipulator featuring six actuators arranged in a parallel configuration between a fixed base and a movable platform. This unique setup allows for six degrees of freedom, with movements in three translational directions (X, Y, Z) and three rotational axes (pitch, roll, and yaw). This complex, multi-axis control makes Stewart Platforms highly suitable for replicating real-world dynamic environments.

Why Use Stewart Platforms as 6-DOF Shake Tables?

Stewart Platforms offer unparalleled control and flexibility that traditional shake tables cannot match. By enabling precise multi-directional movement, they simulate the complex motions essential for various engineering and research applications. From earthquake testing to flight simulation, Stewart Platforms serve as highly adaptable 6-DOF shake tables that meet the rigorous demands of today’s research.

Introducing QuakeLogic’s MOTIONMASTER-6

QuakeLogic is proud to offer the MOTIONMASTER-6, a cutting-edge 6-DOF shake table designed to meet high-performance testing requirements across industries. The MOTIONMASTER-6 includes:

  • 6 Servo Actuators for precise control and high accuracy
  • 6-DOF System for comprehensive simulation of real-world movements
  • Top Table Dimensions: 320 mm in diameter
  • Payload Capacity: 12.5 kg
  • Velocity: Up to 40 mm/s
  • Stroke: 200 mm total for wide-range movement
  • Software: Ready-to-use GUI, API interface (Python and MATLAB), with LabView and MATLAB source codes

Applications of Stewart Platforms and the MOTIONMASTER-6

  1. Earthquake Engineering and Structural Testing
    The MOTIONMASTER-6’s six degrees of freedom allow it to replicate the ground motions experienced during earthquakes, aiding researchers in studying the resilience of buildings, bridges, and infrastructure. The platform helps engineers validate seismic models, test structural designs, and enhance building codes to improve safety.
  2. Aerospace Simulation and Pilot Training
    In aerospace, Stewart Platforms like the MOTIONMASTER-6 are essential for flight simulators, allowing pilots to experience realistic motion scenarios, including turbulence, takeoffs, and landings. This tool is invaluable for training and testing in controlled environments, helping pilots and engineers prepare for real-world conditions.
  3. Automotive Testing and Design
    Stewart Platforms are used to simulate vehicle dynamics, from braking and acceleration to cornering on various surfaces. The MOTIONMASTER-6 helps automotive engineers optimize suspension systems, chassis designs, and drivetrain components, enhancing safety, stability, and performance.
  4. Drone Development and Testing
    The MOTIONMASTER-6 provides a controlled environment to simulate real-world flight conditions, such as turbulence and rapid changes in orientation. This enables engineers to assess drone stability and refine control algorithms for safer, more reliable designs.
  5. Satellite and Antenna Alignment
    For precise positioning, the MOTIONMASTER-6 simulates the movements of satellites and antennas. This platform is used in telecommunications and space exploration to test and calibrate positioning systems, ensuring accurate communication links and data transmission.
  6. Biomedical Device Testing
    Stewart Platforms are used in biomedical research to test devices like prosthetics and surgical instruments. The MOTIONMASTER-6’s precise motion control allows for realistic simulations, ensuring devices can withstand dynamic loads and perform reliably.
  7. Entertainment and Virtual Reality
    The 6-DOF motion capabilities of Stewart Platforms make them ideal for creating immersive experiences in VR and theme park applications. The MOTIONMASTER-6 replicates real-world activities, providing a realistic experience that enhances both entertainment and training programs.

Advantages of Using Stewart Platforms and the MOTIONMASTER-6 as 6-DOF Shake Tables

  • High Precision and Realism: The MOTIONMASTER-6 offers precise control, enabling detailed studies and realistic testing that mirrors real-world conditions closely.
  • Flexibility Across Applications: With its multi-axis capabilities, the platform is versatile enough to meet the needs of various industries, from research to VR simulation.
  • Load Capacity and Structural Stiffness: The platform’s parallel actuator design distributes loads evenly, supporting heavy payloads without sacrificing accuracy.
  • Customizable Motion Parameters: The MOTIONMASTER-6 can be programmed to recreate specific motion patterns or events, such as earthquakes, enabling finely tuned simulations.
  • Real-Time Data Collection and Analysis: Integrated with advanced data acquisition, this platform allows real-time monitoring and analysis, which is essential for applications requiring immediate feedback.

About QuakeLogic

QuakeLogic is a leader in advanced seismic monitoring solutions, offering a range of products and services designed to enhance accuracy and efficiency in testing, data acquisition, and analysis. Our team is committed to pushing the boundaries of motion simulation, providing customizable solutions that meet the specific needs of each industry.

Contact Information

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

Whether for seismic testing, pilot training, or VR experiences, the MOTIONMASTER-6 unlocks new possibilities in research, development, and training. Contact us to learn how our 6-DOF shake table solutions can elevate your 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.