R20 gauge – Wireless extensometer

Technical specifications

Overview of the R20 wireless extensometer

The R20 gauge is a wireless electronic extensometer specifically designed for remote measurement of the spacing or convergence between two points several metres apart, with a resolution of 0.01 mm.

What is a wireless extensometer used for?

The wireless extensometer builds on the physical principles of the mechanical extensometer, also known as a convergence meter, while adding the benefits of a wireless sensor: all readings are taken automatically.

In addition to the linear displacement sensor, an ambient temperature sensor and a relative humidity sensor enable a complete diagnostic and help identify any potential correlation with climatic conditions.

R20 wireless extensometer: operating principle and advantages

Based on the R1 wireless crackmeter, this wireless extensometer shares its main technical and functional features:

• Three integrated sensors: linear displacement, ambient temperature and relative humidity.
• Intuitive configuration in a few clicks, with no IT expertise required.
• Extensive connectivity covering all European countries.
• Long battery life: up to 7 years (depending on data transmission settings).
• Flexible configuration, adjustable remotely.
• Dedicated app accessible from a smartphone or web browser.

A one-year subscription is included with the R20 gauge, starting from first initialization. It can be renewed directly via the app or by purchase order. For further information on how the R1 gauge works, please refer to the R1 gauge product page.

The Invar cable, with its very low thermal expansion coefficient, is cut to length according to the installation context and can be adjusted by ±15 cm on site.

Thanks to data transmission via the app, the R20 gauge can be installed at height, out of reach, or at a more accessible level to facilitate maintenance if required.

Examples of R20 gauge installation on pillars in a church by the company EGSOL

Remote monitoring of the displacement between 2 face-to-face points

The R20 wireless extensometer uses the same operating principles as the G20 gauge to measure the change in distance between two points, A and B, separated by a distance D (in metres).

Point (A) is a ring with a fixing bracket.

Point (B) is a ball-bearing pulley fixed to a bracket, which redirects the Invar wire vertically down to the monitoring station.

An Invar cable (1) is fixed on one side to point (A) and on the other to the counterweight of the station (2). Between its two ends, the Invar wire runs over the ball-bearing pulley (B), fixed to the wall vertically above the station. The counterweight system maintains constant tension throughout the assembly, which ensures that the gauge measures only the change in distance between points (A) and (B).

The choice of Invar cable is crucial to guarantee optimal measurement accuracy. Thanks to its very low thermal expansion coefficient, this material minimizes the effects of temperature variation, which could otherwise affect the reliability of the data. That makes it a key component for stable, accurate measurements, even in environments subject to climatic fluctuations.

The gauge can be fixed at head height. An optional enclosure (3) can be used to secure the gauge where necessary.

Remote monitoring of the displacement between 2 points in the same plane

The R20 wireless extensometer can also be used to measure the distance between two points located in the same plane.

For example, it can monitor the spacing between two points on the same wall, even when they are several metres apart.

In this configuration, a specific optional fixing kit is supplied to ensure a suitable installation on a single plane.

Protective enclosure

An enclosure to protect the R20 wireless extensometer can be ordered as an option.

A key is supplied to lock the enclosure.

Measurement monitoring with the Saugnac app

All the data collected by the 3 sensors is accessible in the Saugnac app from a PC or smartphone. The app is supplied with the R20 gauge and remains accessible even after the subscription for transmitting the gauge’s data has expired.

This very simple app allows you in particular:

• to generate and download graphs
• to download the data in Excel or CSV format
• to set alert thresholds with email notifications
• to change the settings remotely
• to share the data in a single click

The operating principle is the same as for the R1 gauge.