Dynamic Vibrating-WireOperate traditional static gauges at dynamic rates

Overview

Vibrating-wire (VW) sensors are used extensively for monitoring strain, force, pressure, displacement, and tilt in many monitoring applications: bridge, structural health, slope, dams, roads, ground water, and other geotechnical sites. These sensors dominate in these applications because of their ability to provide accurate measurements over very long periods—even decades of unattended monitoring.

Traditional methods to analyze the response from a VW sensor were limited to static measurements only. However, with advancements in technology and the use of a patented spectral-analysis approach, Campbell Scientific is able to use VW sensors for dynamic and simultaneous measurements. This new approach to using time-proven VW sensors in dynamic applications provides several advantages:

• Stable, long-term monitoring
• Dynamic and simultaneous measurements
• VSPECT^®technology with diagnostics to verify the health of each sensor and allow for longer cable lengths, highest precision, and noise immunity
• The ability to use existing VW sensors with no need to replace the installed sensors

Introduction

VW sensors have been used as a trusted measurement technology in the structural industry for several decades. These sensors are used for a variety of measurements including strain, force, pressure, and displacement. VW sensors are differentiated from other types of sensors by their reliability and long-term stability.

The typical speed at which a VW sensor can be measured is every two seconds, which has limited the use of VW sensors in many structural monitoring systems where dynamic measurements are required. Traditionally, VW sensors have only been used for static measurement applications. When faster measurements are required, other technologies—such as resistive-foil sensors—are used.

Campbell Scientific has a long history of developing VW instruments, including both the VW interface and full back-end support using data loggers, data-acquisition systems, communication interfaces, and software products. In 2008, Campbell Scientific introduced VSPECT technology as a fundamental advancement in how VW measurements are made. The patented VSPECT algorithms that lie at the heart of this technology improved the precision of measured values by orders of magnitude over previous methods. Moreover, noise immunity was simultaneously improved by discriminating signal noise based on frequency content.

After introducing the VSPECT technology, Campbell Scientific developed instruments that measure standard single-coil VW sensors at rates well suited for dynamic measurements. This advancement created the opportunity to use existing VW gauges for measurements that previously excluded them.