Measuring principle
The rigid rods of the multi-point extensometer are anchored at one end in specific locations in the soil or rock and slide in protective guide tubes , being free to move in one direction only.
The free ends of the rods are correlated to the instrument head (reference head) fixed at the
surface and form the different measuring points. Distances between the free end of the rods and the reference head ,measured over time, provide the movements of the various anchoring points relative to the head.
Movements are measured manually using a caliper or a dial gauge, or automatically through displacement transducers.
The displacement transducers, fixed on the instrument reference head, can be LVDT, potentiometer or vibrating wire. Depending on the ground movements expected , sensors with different ranges can be chosen.
Reading of the potentiometric transducers can be performed manually with our hand-held read-out units or our portable datalogger DEC 3000; or with our automated datalogger CUM3000
Rod extensometers can be integrated into automatic monitoring systems with real-time monitoring of phenomena and managed with local and remote real-time alarms
In addition, versions with displacement transducers retain the facility to perform manual readings without the need to remove the sensors.
Stainless steel and Invar rods are supplied in lengths of 2 or 3 meters, linkable with threaded pins.
Guide tubes may be made of flexible, single piece nylon or of rigid linkable piping (length 2-3m or on request).
Fiberglass rods are supplied ready assembled in the workshop, to the desired length and complete with anchors and nylon guide tubing.
Stainless steel or Invar steel rods, complete with flexible or rigid protective pipes can be supplied on request.
Rigid pipes can be supplied with ball bushings or Teflon sleeves.
Standard anchors are suitable for cementing into rock or soil
For particular soil conditions or specific installation requirements, special anchors can be made on request.
The reference head is made of stainless steel complete with protective cap. this facility allows control and reliability of electrical measurement and continued readings in the case of maintenance to or replacement of the sensor.
Fiberglass rods are supplied ready assembled from the workshop, of the desired length and complete with anchors and protective sheath with nylon guide tube.
Technical Specifications
| Version |
Glass Fiber |
Stainless Steel |
Invar |
Wire in stainless steel |
| Diameter |
7mm |
8mm |
8mm |
3mm |
| Weight/meter |
0,09 Kg/m |
0,4 Kg/m |
0,41 Kg/m |
– |
| Young’s Modulus |
20 GPa |
200 GPa |
140 GPa |
200 GPa |
| Coefficient of thermal expansion |
3 ppm/°C |
17 ppm/°C |
1 ppm/°C |
17 ppm/°C |
| Junction |
Continuous |
Continous
Threaded Bars M/F |
Continous
Threaded Bars M/F |
Continuous |
| Protective Sheath |
nylon Ø 12 mm
tubo PVC da 1/2” |
In rods 3M long |
In rods 3M long |
Nylon or PVC tube |
| Anchorages |
Galvanized steel L=500 mm |
Galvanized steel L=500 mm |
Galvanized steel L=500 mm |
Galvanized steel L=500 mm |
| Reference head |
Stainless steel |
Stainless steel |
Stainless steel |
Stainless steel |
Vibrating Wire Transducer
| Technology |
Vibrating Wire |
| Temperature Sensor |
On board |
| Range |
5 ÷ 50 mm |
| Accuracy |
± 0,2% f.s. (Including linearity, hysteresis and repeatability) |
| Linearity |
<±0,02%f.s. |
| Resolution |
<0,02% f.s. |
| Frequency Range |
500 Hz ÷ 1000 Hz |
| Operating temperature |
-20°C÷ |
| Power Supply |
From Datalogger |
| Material |
Stainless Steel |
| Inner Rod |
Stainless Steel |
| Anchor Types |
Dowels, threaded bars, fixtures |
| Protection |
IP67 or IP68 up to 10 atm |
| Signal Cable |
2 x 0,5 – 3x 0,5 with thermistor on board |
| Max Distance to Datalogger |
1000 mt |
Potentiometer Transducer
| Technology |
Linear Potentiometer |
| Temperature Sensor |
On board |
| Range |
5 ÷ 50 mm |
| Repeatability |
0,01mm |
| Linearity |
±0,1 % f.s. |
| Resolution |
Dependent on datalogger |
| Power Supply |
9÷36 V |
| Material |
Stainless Steel |
| Inner Rod |
Stainless Steel |
| Anchor Types |
Dowels, threaded bars, fixtures |
| Protection |
IP67 (IP68 up to 10 atm on request) |
| Signal Cable |
2 x 0,5 – 3x 0,5 with thermistor on board |
| Max Distance to Datalogger |
1000 mt |
DEVICES FOR MANUAL READINGS
| MODEL |
Caliper |
Dial Gauge |
| Range |
200mm |
50mm |
| Resolution |
± 0,1 mm |
± 0,01mm |
| Accuracy |
± 0,2 mm |
± 0,02mm |
ACCESSORIES AND RELATED PRODUCTS
| Caliper |
Device for the manual reading of rod extensometer |
| Dial Gauge |
Device for the manual reading of rod extensometer |
| Junction Boxes |
Available in different models for the connection to different instruments |
| Multiwire Cable |
Available with different conductors for the connection of different sensors to one cable |
| DEC 5 |
Portable Readout Unit |
| DEC 3000 |
Portable Datalogger |
| CUM 3000 |
Multichannel Datalogger |
| MUX |
Multiplexer for the connection of different sensors to Datalogger |
Technical Assistance
If you have any requests or questions about our instruments or if you have special needs that require different solutions from the standard, please contact us. Our team will provide all the necessary information and will be very happy to work with you to study, develop and customize instruments and solutions suitable for your specific needs.
All information in our datasheet is subject to change without prior notice.
Please check the datasheet/details carefully and contact Pizzi Instruments for further information.
