Vibrating Wire Load Cells

Applications
The measurement and control of load including: Load in rockbolts, tie backs, foundation anchors and tunnel support Tension in cable anchors and multistrand tendon anchors
Operating Principle
The vibrating wire load cell comprises a set of three or six vibrating wire gauges, mounted parallel to each other equally spaced in a ring in an alloy steel cylindrical housing. The method of construction results in a very robust instrument suitable for use where high performance, longevity and mechanical strength are important. A heavy gauge, multicore, sheathed cable connects the cell to the readout unit. The mode of operation is by electrical plucking of the vibrating wire. The change in load acting on the load cell is proportional to the difference of the squared frequency of vibration for the corresponding load. The readings are taken on EKE 871, EKE 875 or EKE 878 Dataloggers
Advantages

• Accurate, robust and very good long term stability Negligible temperature effects compared with oil filled load cell
• Fast response time
• Accuracy unaffected by cable length
• Suitable for remote readings
• Capable of reading eccentric loads
• Common readout for all vibrating wire type instruments

Installation
Tensile loads in rockbolts and cables are measured by installing Centre Hole load Cells between the rock/concrete face and the tensioning nut of the bolt or anchor. For the most reliable results, a concrete bearing pad should be cast, with its upper face flat and perpendicular to the bolt or cable. A bearing plate is placed beneath the cell to spread the load and to take up any residual nonalignment. A further bearing plate is placed between the cell and anchor. The assembly is centralised and held in place by applying a small tension to the bolt or cable. Fault in centralisation or alignment will be apparent from differences in load readings at each of the vibrating wire gauges in the cell. In situations where speed of installation is important, the bearing pad may be formed using high alumina cement or resin grout. Readings of the vibrating wires are averaged to obtain the bolt or cable tension. In multi-strand cable anchors, it is possible to tension the strands uniformly, by monitoring and balancing the load reading for each of the vibrating wire gauges.
Product Code: EKE 831 to EKE 836
Operating Principle

• The vibrating wire load cell comprises a set of three or six vibrating
• wire gauges, mounted parallel to each other equally spaced in a ring in
• an alloy steel cylindrical housing. The method of construction results
• in a very robust instrument suitable for use where high performance,
• longevity and mechanical strength are important. A heavy gauge,
• multicore, sheathed cable connects the cell to the readout unit. The
• mode of operation is by electrical plucking of the vibrating wire.
• The change in load acting on the load cell is proportional to the
• difference of the squared frequency of vibration for the corresponding
• load. The readings are taken on EKE 871, EKE 875 or EKE 878 Dataloggers

Advantages

• Accurate, robust and very good long term stability
• Negligible temperature effects compared with oil filled load cell
• Fast response time
• Accuracy unaffected by cable length
• Suitable for remote readings
• Capable of reading eccentric loads
• Common readout for all vibrating wire type instruments

Installation
Tensile loads in rockbolts and cables are measured by installing Centre Hole load Cells between the rock/concrete face and the tensioning nut of the bolt or anchor. For the most reliable results, a concrete bearing pad should be cast, with its upper face flat and perpendicular to the bolt or cable. A bearing plate is placed beneath the cell to spread the load and to take up any residual nonalignment. A further bearing plate is placed between the cell and anchor. The assembly is centralised and held in place by applying a small tension to the bolt or cable. Fault in centralisation or alignment will be apparent from differences in load readings at each of the vibrating wire gauges in the cell. In situations where speed of installation is important, the bearing pad may be formed using high alumina cement or resin grout. Readings of the vibrating wires are averaged to obtain the bolt or cable tension. In multi-strand cable anchors, it is possible to tension the strands uniformly, by monitoring and balancing the oad reading for each of the vibrating wire gauges.
EKE 831 to EKE 836
Comprising alloy steel cylinder with three gauges at 120º in the cylinder walls. Each gauge is fixed with non-slip cylindrical end clamps. Electromagnetic pulsing and sensing units with, over voltage surge arrestors are mounted adjacent to each wire on the outer face of the cylinder. The entire unit is then protected by an outer zinc plated steel sleeve with ‘O’ ring seals.
Same as EKE 831 to EKE 836, but with six parallel Vibrating Wire Gauges, located 60º apart in cylinder wall. Centre Hole Bearing Plates Centre Hole Bearing Plates comprising epoxy painted steel discs with central hole for use with EKE 831 to EKE 839 load cells for monitoring tension in rockbolt or cable anchors. The plates incorporate three location dowels to assist concentric mounting of the load cell. Details of dimensions as tabulated
Installation Accessories

• EKE 83131 Connecting Cable
• For use with EKE 831 to EKE 836 Vibrating Wire load Cells. Six Conductor Copper Wire, insulated colour coded and screened with sheathing
• EKE 83731 Connecting Cable for use with EKE 837 to EKE 839 Vibrating Wire load Cells, twelve Conductors, copper wire insulated, colour coded and screened with sheathing
• EKE 83125 Splicing Set To be used with EKE 83131connecting cable
• EKE 83725 Splicing Set To be used with EKE 83731 connecting cable

Product Code: EKE 837 to EKE 839

Details

• Same as EKE 831 to EKE 836, but with six parallel Vibrating Wire Gauges, located 60º apart in cylinder wall. Centre Hole Bearing Plates
• Centre Hole Bearing Plates comprising epoxy painted steel discs with central hole for use with EKE 831 to EKE 839 load cells for monitoring tension in rockbolt or cable anchors. The plates incorporate three location dowels to assist concentric mounting of the load cell. Details of dimensions as tabulated :

Installation Accessories

• EKE 83131 Connecting Cable
• For use with EKE 831 to EKE 836 Vibrating Wire load Cells. Six Conductor Copper Wire, insulated colour coded and screened with sheathing
• EKE 83731 Connecting Cable for use with EKE 837 to EKE 839 Vibrating Wire load Cells, twelve Conductors, copper wire insulated, colour coded and screened with sheathing
• EKE 83125 Splicing Set To be used with EKE 83131connecting cable
• EKE 83725 Splicing Set To be used with EKE 83731 connecting cable