Controls Group http://www.controls-group.com/images/logo_controls.gif Mini On-sample transducers for local strain measurement in triaxial testing Mini On-sample transducers for local strain measurement in triaxial testing
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Soil mechanics

Mini On-sample transducers for local strain measurement in triaxial testing

Main features
  • Suitable for specimen diameters from 38 to 150mm
  • Maximum working pressure of 3400 kPa
  • Light and compact construction suitable for advanced triaxial cells
  • Axial and radial deformation measured directly on the triaxial test specimen
  • Suitable  for static and dynamic data acquisition by triaxail systems 
General description
General description
In conventional triaxial testing the stiffness of a soil specimen is determined  by external measurement of displacement.  Such measurement are subjected to errors caused by deflections of loading system and bedding of the porous stone onto the ends of the specimen. 
Local axial and radial strain transducers avoid these problems by providing the opportunity to measure  the deformation, with high accuracy, directly on the triaxial test specimen.
Lacal strain transducers are supplied in a kit which includes one radial and two axial transducers suitable for 38mm, 50mm,70mm, 100mm and 150mm specimen diameters. Mounting accessories such as radial belt, mounting brackets and jig are also inclueded.
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Technical specifications

  • Input voltage: 10 V
  • Output voltage (ratiometric): ± 350mV (radial); ±950mV (axial)
  • Accuracy (average): better than ±0.5% FRO
  • Temperature coefficient:  ± 0.02/FRO/°C
  • Weight:   
  • dia.(mm) radial(g) axial(g)
    38 28 9
    50 34 10
    70 46 11
    100 65 12
    150 95 14

Ordering info

SUITABLE FOR STATIC TESTS

28-WF4039/KM  
Mini-On sample transducer kit for 38mm dia. samples with two linear and one radial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for static tests.    

28-WF4059/KM 
Mini On-sample transducer kit for 50mm diameter samples with one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for static tests.   

28-WF4079/KM  
Mini On-sample transducer kit for 70mm diameter samples with one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for static tests.

28-WF4109/KM  
Mini On-sample transducer kit for 100mm diameter samples with one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for static tests. 

28-WF4159/KM 
Mini On-sample transducer kit for 150mm diameter samples one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for static tests.


SUITABLE FOR DYNAMIC TESTS (Dynamic triaxial system

28-WF4039/KN  
Mini On-sample transducer kit for 38mm diameter samples one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for dynamic tests.

28-WF4059/KN
Mini-On sample transducer kit for 50mm diameter samples one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for dynamic tests.    

28-WF4079/KN
Mini-On sample transducer kit for 70mm diameter samples one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for dynamic tests. 

28-WF4109/KN
Mini On-sample transducer kit for 100mm diameter samples one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for dynamic tests.   

28-WF4159/KN
Mini On-sample transducer kit for 150mm diameter samples one radial and two axial miniature transducers, radial belt, axial fixing pads and  plugs. Suitable for dynamic tests.

The transducers mentioned above are also available with traceable calibration certificates 28-WF4XXX/KMC or 28-WF4XXX/KNC

Additional Information

The local strain transducer has a built-in Hall effect sensor on one end and a magnet on the other.  The sensor is a device that detects the presence of a magnetic field, generated by a flat rectangular piece of P-type semiconductor material (Hall element) and a power source that supplies it with a constant current.  The flow of positively charged particles (or hole flow) takes place inside the P-type semiconductor material.
When current is passed through the conductor and it is placed in a magnetic field perpendicular to the current flow, a voltage difference, called the Hall voltage, is generated transverse to both the current and the magnetic field.  This is known as the Hall effect.
When flux lines that are perpendicular to the Hall element pass through it, the carriers are deflected to one side by an effect called the Lorentz force.
The angle at which the magnetic flux lines pass through the Hall element affects the amplitude of the voltage produced at the output.  Maximum output is achieved when the lines are perpendicular.

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