VW Crackmeter
Typical applications include:
- Monitoring joints for unexpected movement to provide early warning of performance problems
- Monitoring joints and cracks in structures that may be affected by nearby excavation and construction activities.
- Monitoring cracks in structures that have experienced seismic activity.
Advantages of the VW Crackmeter:
- High Accuracy – The VW crackmeter provides a repeatability of 0.3 mm.
- Two Ranges – The VW crackmeter is available in 60 and 100-mm ranges (2.4 and 4 inches).
- Temperature Measurement – The VW crackmeter is equipped with a temperature sensor.
- Manual or Automatic Readings – The crackmeter connects easily to a data logger for unattended monitoring.
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VW Crackmeter Specifications
| VW CRACKMETER KITS | |
|---|---|
| 60mm, Waterproof | 52636388 |
| 100mm, Waterproof | 52636389 |
| The VW Crackmeter consists of two components: a vibrating wire displacement sensor and a set of anchors. Signal cable, ordered separately, is connected to the sensor at the factory. | |
| Sensor Type | Vibrating wire. A built-in thermistor provides temperature measurements. |
| Range | 60 mm or 100 mm |
| Resolution | 0.025% FS with VW Data Recorder |
| Calibration Accuracy | ±0.1% FS |
| Repeatability | ±0.5% FS |
| Waterproof Rating | Rated to 17 bar (250 psi) |
| Materials | Stainless steel body and shaft, Neoprene O-rings, plated-steel swivels, mild-steel anchors |
| Nominal Length | 60 mm crackmeter is 400 mm (15.7″) long; 100 mm crackmeter is 530 mm (21″) long |
| SIGNAL CABLE | ||
|---|---|---|
| Signal Cable | 50613824 | Shielded cable with four 22-gauge tinned copper conductors and polyvinyl chloride (PVC) jacket. Specify cable length for each sensor. |
| EXTRA ANCHORS | ||
|---|---|---|
| Anchor Set | 52636080 | Set of two groutable anchors. Needed if the crackmeter is moved to a new location |
| Ball Joint | 02700196 | One ball joint. Needed if either of the original ball joints supplied with the crackmeter are damaged or corroded. |
| TERMINAL BOXES | |
|---|---|
| Terminal Box for 6 sensors | 57711606 |
| Terminal Box for 12 Sensors | 57711600 |
| Terminal Box for 24 Sensors | 97711624 |
| Provides terminals for signal cable from 6, 12, or 24 sensors. Sensors are selected by rotary switch. Small 6-sensor box is 240 x 190 x 120 mm (9.5 x 7.5 x 4.75″). Larger 12 and 24-sensor box is 290 x 345 x 135 mm (11.5 x 13.5 x 5.25″). | |
| READOUTS |
|---|
| Compatible readouts include the VW Data Recorder and other pluck-type VW readouts. See separate data sheets for details. |
| DATA LOGGERS | |
|---|---|
| 1-Channel V-Logger | 52615110 |
| 4-Channel V-Logger | 52615140 |
| Campbell Scientific Data Loggers | VW displacement transducers connect directly to the V-Logger and Campbell Scientific CR6. Campbell Scientific CR1000XE requires an AVW200 vibrating wire adapter. See separate data sheets. |
VW Displacement Sensor Specifications
| VW DISPLACEMENT SENSORS | ||
|---|---|---|
| Range | Length | Part Number |
| 12.5mm | 195mm | 92636135 |
| 25mm | 243mm | 92636255 |
| 50mm | 275mm | 92636055 |
| 75mm | 369mm | 92636075 |
| 100mm | 400mm | 92636335 |
| 150mm | 530mm | 92636155 |
| 200mm | 660mm | 92636205 |
| 300mm | 917mm | 92636305 |
| 500mm | 1433mm | 92636505 |
| Sensor Type | Vibrating wire. A built-in thermistor provides temperature measurements | |
| Thermistor | 3k Ohms at 25 °C | |
| Over-Range | Range + 20% | |
| Resolution | 0.025% FS | |
| Calibration Accuracy | ±0.1% FS | |
| Non linearity | <0.5% FS | |
| Frequency Range | 1650 – 2700 Hz | |
| Nominal zero value | 1850 Hz | |
| Waterproof Rating | Waterproof crackmeter is rated to 16 bar (232 psi) | |
| Diameter | 12.5mm to 300mm range are 13mm in diameter. 500mm range is 16mm in diameter | |
The VW crackmeter consists of a VW displacement transducer and a mounting kit. Anchors are installed on opposite sides of the crack and the transducer is mounted across the anchors. A change in the distance across the crack causes a change in the frequency signal produced by the VW displacement transducer when excited by the readout or data logger.
The readout device processes the signal, applies calibration factors, and displays a reading in millimeters or inches. The initial reading is used as a datum. Subsequent readings are compared to the datum to calculate the magnitude, rate, and acceleration of movement across the crack.
