Digital Tape Extensometer


The digital tape extensometer is used to detect and monitor changes in the distance between two reference points. Typical applications include:

  • Monitoring convergence of tunnel walls.
  • Monitoring deformations in underground openings.
  • Monitoring displacement of retaining structures, bridge supports, and other structures.
Digital Tape Extensometer


Stainless steel reference points are permanently installed at measurement stations along the tunnel or structure. To obtain a measurement, the operator stretches the tape between two reference points, hooking the free end of the tape to one point and the instrument body to the other. The operator tensions the tape by turning a knurled collar until two index marks are aligned and then notes the reading from the tape and the digital display. The sum of these readings is the distance between the two reference points. By comparing the current reading to the initial reading, the operator can calculate the change in distance between the two reference points.


Repeatable Measurements: The digital tape extensometer provides extremely repeatable measurements over spans up to 30 meters or 100 feet. The new digital display makes measurements easy.

Economical Reference Points: Stainless steel eyebolt reference points are economical and easy to keep clean. The eyebolts can be bolted or welded to the structure or threaded into groutable or expansion-type anchors.

Rugged: Precision parts are protected by a strong aluminum body and a plastic lens.

Easy to Use: The digital tape extensometer’s hook and eyebolt system is easy to use and offers unrestricted angular movement of the tape. Tape tension is easy to adjust, even when the operator wears gloves.

digital tape extensometer screen

For more information

Please download the datasheet and the manual for the Digital Tape Extensometer. These documents can be viewed and printed with Adobe Acrobat Reader.

Digital Tape Extensometer Specifications

Unit with 20 m tape51811510
Unit with 30 m tape51811530
Measurement Repeatability± 0.10 mm.
Steel Tape13 mm x 20 m or 13 mm x 30 m, perforated at 50 mm intervals, graduated in mm. Thermal coefficient of expansion is 11.6 ppm per degree.
Dimensions70 mm OD, 610 mm overall length.
WeightApproximately 2 kg
BatteriesSR44 silver oxide cell. Battery life is approximately 3 years.
Operation Temperature0 to 40 °C.
English Tape Extensometer
Unit with 66' tape51811500
Unit with 100' tapeSpecial Order
Display Resolution0.0005 inch
Measurement Repeatability± 0.005"
Steel Tape0.5" x 60 or 0.5" x 100', perforated at 2-inch intervals with 1/8"graduations. Thermal coefficient of expansion is 6.45 ppm per degree F
Dimensions2.75" OD, 24" overall length
WeightApproximately 4.5 lb
BatteriesSR44 silver oxide cell. Battery life is approximately 3 years
Operation Temperature0 to 40 °C
Reference Point51812000Stainless steel eyebolt with lock nut. Threads into groutable or expansion anchor
Groutable Anchor51804304Steel rebar tapped to accept reference point. #5 rebar x 4" long (16 x 101 mm ).
Expansion Anchor51812050Tapped for reference point. Requires 35 mm (1.375") drill hole.
Carrying Case51812100Sturdy vacuumed formed ABS plastic carrying case with foam lining for shock protection.
Metric Replacement Tape, 20 m11801370
English Replacement Tape, 66'11801380