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Profile of Vibrating Wire Technology
Vibrating wire weighing technology originated in the 1950s in heavy-duty mining, civil and hydrological load cell application where its reliability and drift-free performance was well suited to the need. Specially re-engineered and adapted for process feeding and weighing application in the 1970s, the technology has been the focus of continuing advancements over the last 40 years.

Vibrating wire weight sensors exploit the well understood relationship between a wire’s tension and its resonant frequency. Today, the technology is used in high-performance all-digital weighing applications where the load to be measured directly governs the tension of the wire, and the resulting frequency of vibration is detected and evaluated to obtain the weighment.

In operation, a thin, electrically conductive wire is mechanically fixed at both ends and the load to be measured is applied to the wire, increasing its tension. The wire is also immersed in a magnetic field produced by flanking permanent magnets. Connected to an amplifier circuit, the wire is driven to oscillate through the application of current. Wire oscillation within the magnetic field causes, in turn, the induction of a millivolt level signal, which is fed back to the differential input of the amplifier to enable the maintenance of resonant oscillation.

On-board circuitry then produces a square-wave output of wire vibration which is transmitted to the weight processing system for high-resolution frequency counting, linearization, temperature compensation, and dynamic filtering.

In 1976 Coperion K-Tron introduced the process industry‘s first truly digital load cell. After three decades and five generations of innovation and development, Coperion K-Tron‘s Smart Force Transducer technology continues to set the standard for the industry. Advanced single-wire design, high resolution, internal force reduction, and 90% fewer parts combine to provide the highest possible levels of performance and reliability.

The SFT II Medium and Large are employed in all Coperion K-Tron’s platform and three-point suspension scale loss-in-weight feeding systems. The SFT III is optimized for direct, single-point weighing and is used in Coperion K-Tron’s Smart Weigh Belt Feeders, K4G Blender, and Smart Flow Meters.

SFT Vibrating Wire Weighing Technology Features:

  • 100% digital design, no calibration required
  • Advanced single wire weighing technology
  • Resolution of 1:4,000,000 in 80 ms
  • Weight captured, linearized and temperature compensated 112 times per second
  • Zero data loss measurement
  • Integrated force reduction
  • Digital low-pass filter reduces effect of plant vibration
  • Waterproof and dust tight
  • Stand-alone RS485 network connected for multiple load cell systems
  • On-board microcontroller, custom frequency processor, calibration memory and voltage regulator
  • Hazardous area models available for European (ATEX) and North American (NEC) standards.