Vibrating Wire Centre Hole Load Cell

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 load reading for each of the
vibrating wire gauges.

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