The Elasto-Magnetic sensor (EM sensor) which can measure the force in steel cable directly has been used in infrastructures of cable bridges, pre-stressed concrete structures, earth anchor systems, tie-back systems, and architectures. The EM sensor is based on the magneto-elastic phenomenon of ferromagnetic material discovered in 1862. The magnetic properties of ferromagnetic material are dependent on applied mechanical stress, such as pull, bend and torsion. The EM sensor has been approved to be an effective means of non-contact and direct determination of the stress/force in steel components with a high accuracy in which the accuracy has within 2% difference from load cell. The cover of the sensor is carbon steel with chrome coating. Polyurethane fills the inside of the sensor. All circuit and connection are protected using epoxy sealant.
The EM sensor is composed of a primary coil and a secondary coil (sensing coil) by passing current through primary coil. Ferromagnetic material is magnetized sensing coil picks up induced electromotive force that is proportional to change rate of applied magnetic flux and relative permeability. As permeability of core changes, output voltage changes. The output voltage is calibrated to measure force.
Applications
o Cable-supported Bridge ○ Steel Hanger
o PC Tendon ○ Earth Anchor
o Nuclear power plant
The PowerEM™ is a stand-alone and easy-to-use reading units for the type of EM sensors from 12.7mm (0.5”) strand to 250mm bundle cable. The unit can take the temperature reading from the temperature sensor inside an EM sensor and compensate for the temperature effect of the steel. It is housed in a cast aluminum enclosure. A rugged, weather-resistant enclosure designed for use in field environments is available. The unit can store 16 types, total 1024 EM sensors parameters. User-friendly Windows® based software allows easy programming of sensor channels, selecting sensor types, setting of calibrations, and taking measurement. A PowerEM is available to use a multiplexer with upto 16 channels.
This software is developed to control the EM sensor, read-out units, and calibration through PC. The interface for communication between PowerEM and PC is RS-232.
