VW Displacement Gauge 5000
Geosense® VWDT-5000 series of vibrating wire displacement transducers cover displacement ranges up to 300mm and are fully waterproof to a minimum of IP68 (16 bar external pressure). They can be incorporated into many displacement products such as crack and joint meters, convergence meters, soil extensometers and displacement meters.
VWDT-5000 transducers are particularly rugged, and are carefully constructed and thermally aged to minimise long term drift and changes in calibration. The gauges will withstand demanding environmental factors encountered in Civil Engineering construction sites such as tunnels and piling applications.
The data from the VWDT-5000 can be monitored by means of a portable read-out unit or connected to a data logger and distributed if required by telemetry.
Vibrating wire instruments output a frequency signal, and are therefore insensitive to resistance changes in connecting cables caused by contact resistance or leakage to ground. Cable may be readily and simply extended on site without special precautions. Gauges may be read up to 1000 metres away from their installed location, without change in calibration.
Instruments may be read by any commercially available Vibrating wire readout system operating on either the pluck pulse or swept frequency excitation principle, provided that these units operate over the frequency range of the instruments. In addition, these instruments can be data-logged by a variety of data-loggers equipped with vibrating wire excitation modules including Campbell Scientific and Datataker units.
Units are supplied with a M6 female threaded connection on the measuring plunger.
LP Displacement Gauge 5510
Geosense® LPDT-5510 series of linear potentiometer displacement gauges cover displacement ranges up to 75 mm.
They can be incorporated into many displacement products such as rod extensometers, crack meters and displacement gauges.
Constructed from aluminium alloy and stainless steel they are lightweight but robust making them ideal for the harsh environments found within civil engineering.
The data from the Geosense® LPDT-5510 can be monitored by means of a portable read-out unit or connected to an automatic data acquisition system.
VW Displacement Gauge 6000
Geosense® VWDT-6000 series of spring-loaded vibrating wire displacement transducers which cover displacement ranges up to 75mm and are fully waterproof to a minimum of IP68 (16 bar external pressure). They can be incorporated into many displacement products such as crack joint meters, convergence meters, soil extensometers and displacement meters.
VWDT-6000 transducers are particularly rugged, and are carefully constructed and thermally aged to minimise long term drift and changes in calibration. The gauges will withstand demanding environmental factors encountered in Civil Engineering construction sites such as tunnels and piling applications.
The data from the VWDT-6000 can be monitored by means of a portable read-out unit or connected to a data logger and distributed if required by telemetry.
Vibrating wire instruments output a frequency signal, and are therefore insensitive to resistance changes in connecting cables caused by contact resistance or leakage to ground. Cable may be readily and simply extended on site without special precautions. Gauges may be read up to 1000 metres away from their installed location, without change in calibration.
Instruments may be read by any commercially available Vibrating wire readout system operating on either the pluck pulse or swept frequency excitation principle, provided that these units operate over the frequency range of the instruments. In addition, these instruments can be data-logged by a variety of data-loggers equipped with vibrating wire excitation modules including Campbell Scientific and Datataker, units.
Units are supplied with a ball end to ensure minimum contact point to ensure accurate readings.
VW 3D Crack Meter 4600
Geosense® VWTCM-4600 3D crack meters monitor three-way displacement across cracks and joints in concrete, rock, soil and structures.
The central reference block allows the vibrating wire transducers to show independent movement in all directions, irrespective of each other.
The VWTCM-4600 comprises a 3D mounting frame comprising two arms and two groutable anchors and three vibrating wire displacement transducers complete with built-in thermistors.
Groutable anchors are installed either side of a joint or crack; the installation jig provided ensures that the two anchors are positioned correctly. Once they are set in position the installation jig is removed and the the VWDT-6000 transducers installed. They are positioned against the reference block and typically set to their mid-point.
Any movement in the monitored position will result in relative change between the two anchors which will cause one or more of the VW transducer rods to move independently, thus changing the frequency of the wire. This change in frequency is converted to show the movement in millimetres.
Typically, signal cables run from the sensors to a data logger for remote reading. Alternatively, a terminal/junction box is used and a handheld readout or data logger is used to record the readings manually.
An initial datum reading is taken, which is then compared to all subsequent readings to give the change and magnitude of displacement.
VW Crack Meter 4000
Geosense® VWCM-4000 crack meters are used to measure movement across surface cracks and joints in concrete, rock, soil and structures.
They consist of a sensor outer body tube and an inner free-sliding rod which is connected at the internal end to a vibrating wire sensor by a spring. At the sensor end of the outer body and the external end of the rod anchors are attached which can be fixed either side of a crack to be monitored.
The gauge operates on the principle that a tensioned wire, when plucked, vibrates at its resonant frequency. The square of this frequency is proportional to the strain in the wire. Around the wire is a magnetic coil which when pulsed by a vibrating readout or data logger interface plucks the wire and measures the resultant resonant frequency of vibration.
A change in distance between the anchors caused by the crack opening or closing causes the inner free-sliding rod to move within the outer body which changes the tension on the spring and the vibrating wire thus altering the resonant frequency of the wire.
VWCM-4000 crack meters are installed by grouting, bolting, bonding or fixing expandable anchors to the structure to be monitored. The anchors incorporate ball joints where they are fixed to the gauge to accommodate any differential cross-axis movement and prevent the inner rod from binding within the outer casing.
LP Crack Meter 4500
Geosense® LPCM-4500 crack meters are used to measure movement across surface cracks and joints in concrete, rock, soil and structures.
They consist of a potentiometric displacement transducer housed in an aluminium body with a stainless steel shaft with two anchoring points.
The potentiometer works on the principle of an outer body tube and an inner free-sliding wiper which makes electrical contact along a strip of fixed resistance. A regulated DC voltage is applied to the two ends of the resistance strip and the voltage between one end of the strip and the contact point of wiper and strip is measured as the output signal. On board signal conditioning provides an output signal in 4-20mA.
LPCM-4500 crack meters are installed by grouting, bolting, bonding or fixing expandable anchors to the structure to be monitored. The anchors incorporate ball joints where they are fixed to the gauge which accommodate any differential cross-axis movement and prevent the inner rod from binding within the outer casing.
Manual 3D Crack Meter
The Geosense® manual 3D crack meters are designed to monitor three way displacement (X, Y and Z) across joints or cracks between adjoining concrete and rock structures.
It comprises of two steel blocks A & B. One (A) having flat machined discs mounted on the X,Y, Z axes and the other (B) having matching machined discs through which the stem of a manual dial gauge can be placed to measure any movement in any axis.
The re-bar anchors on the bottom of each block are grouted adjacent to each other into the structure that is being measured.
VW Joint Meter
The Geosense® Vibrating Wire Joint meter is developed to monitor joints of mass concrete structures.
The instrument consists of two parts, a socket and the main body with a waterproof vibrating wire sensing gauge. During construction of the structure, the socket is secured to the form and embedded into a lift of the block to be constructed. After removal of the form, and prior to concreting of adjacent block, the gauge is screwed into the socket, set at the desired range and then embedded into concrete.
Opening and closing of joint is then measured by the gauge, which is firmly anchored in both blocks. The instrument body includes universal joints, on which sensing element is mounted, accommodating a small degree of shear movement that might occur.
The vibrating wire joint meter is a robust and accurate instrument with excellent long-term stability. It can be measured by vibrating wire portable readout units or a data logger if remote continuous monitoring of the joints is required. All measurements are compared to an initial datum reading, providing a history of magnitude and rate of movement at the joint.