G6 Gauge

Technical specifications

Presentation of the G6 gauge for 2-axis crack monitoring

The G6 gauge is designed to measure changes in the opening (gap) and shear displacement of crack edges, or any type of joint, within a single plane.
The combination of 2 verniers — for translation and rotation — allows the device to track deformation changes under different stress conditions.

A: Axis of rotation, B: Crack

This device is recommended for studying cracks with uneven edges — wider at one end — typically caused by differential settlement or subsidence.

More generally, the G6 gauge is used to monitor any movement along 2 axes: an opening and a shear displacement between 2 structures. When used with an aluminium angle bar, it is also possible to monitor settlement and opening between two structures meeting at an angle (see installation examples below).

Each gauge has a unique QR code and identifier, enabling direct monitoring within the Saugnac application supplied with the product.

Illustrative example: subsidence of the subfloor.

How to install the G6 gauge

Two fixing methods are available for the G6 gauge:

• By adhesive bonding: fixing is quick and easy using the supplied double-sided self-adhesive tabs. On smooth surfaces — partitions, interior walls, wallpaper or thin plaster — the self-adhesive tabs alone will be sufficient.
  If necessary, particularly if the surface is not completely flat or has irregularities, bonding can be reinforced with a fast-curing twin-syringe epoxy adhesive.
• By mechanical fixing: for rough, damp or difficult surfaces, fix using large-head screws. The G6 gauge is pre-drilled with 3 holes of ø 4 mm, making mechanical fixing straightforward on any surface type.
  For difficult surfaces (crumbling, dusty, uneven or damp), mechanical fixing is recommended to prevent any risk of detachment. Bags of 50 screws and wall plugs are available, as well as a ready-to-use mechanical fixing kit including a 4 mm drill bit, a screwdriver and 40 plugs and screws.

Installation examples:

Mechanical fixing of the G6 gauge on a breeze-block wall

G6 gauge fixed with supplied self-adhesive tabs on a crack with uneven width

G6 gauge installed with an extension (using an intermediate plate)

Two G6 gauges positioned at right angles for monitoring vertical cracks

G6 gauge installed for monitoring oblique cracks

G6 gauge combined with a G3 gauge in a church to monitor both 2-axis deformation and misalignment

G6 gauge installed at an angle using an aluminium angle bar

G6 gauges installed on a crack in the wall of the Ishtar Gate

Installation tips

Ideally, the gauge should be fixed so that the arm is perpendicular to and straddles the crack.
To make movement interpretation easier, it is recommended to position:

• The T vernier triangle between 10 and 11
• The R vernier triangle between 50 and 51

This ensures that the sliding tongue arm is parallel to the long side of the gauge body.

Example of correct positioning with T vernier between 10 and 11, and R vernier between 50 and 51

Protection

The G6 gauge can be protected by a transparent PPMA sheet measuring 150 × 300 × 1.1 mm.
This protection is recommended when the gauge is installed in busy areas, schools or public places.

Fixing the G6 gauge and its protective cover with impact anchors

In locations with heavy footfall and a significant risk of damage, the removable E1 gauge with P2E1 plates for 2-axis monitoring may be used instead. After each reading, only the transparent plates remain on the surface, eliminating any risk of damage.

How to read the G6 gauge on 2 axes

For the T vernier (translation):

• The upper scale is graduated in mm from 0 to 30: this is the main measurement scale.
• The lower section with the T marker is mobile: this is the vernier scale to 1/10th of a mm (10 vernier divisions correspond to 9 mm on the main scale).

For the R vernier (rotation):

• The lower scale is graduated in mm from 40 to 70: this is the main measurement scale.
• The upper section with the R marker is mobile: this is the vernier scale to 1/10th of a mm (10 vernier divisions correspond to 9 mm on the main scale).

a) Reading the mm value:
For vernier T, the T marker sits between graduations 10 and 11 on the main scale: the reading is therefore 10 mm.
For vernier R, the R marker sits between graduations 49 and 50 on the main scale: the reading is therefore 49 mm.

b) Reading the decimal value:
Find the vernier line that aligns with a line on the main scale.
For vernier T, graduation 7 aligns with a line on the main scale: the decimal value is therefore 7/10th of a mm.
The T reading is therefore 10.7 mm.

For vernier R, graduation 9 aligns with a line on the main scale: the decimal value is therefore 9/10th of a mm.
The R reading is therefore 49.9 mm.

How to obtain X and Y axis values

To make rotation interpretation easier, X and Y values can be calculated using the following reference frame:

• The origin corresponds to the centre of the disc
• The X axis corresponds to the main axis of the sliding tongue in its initial position
• The Y axis corresponds to the axis perpendicular to X passing through the centre of the disc

The diagram below shows an example where the gauge body is intentionally not aligned with the sliding arm, in order to clearly illustrate the reference frame principle.

The initial position at installation defines the reference frame. For ease of interpretation, it is recommended to fix the gauge body parallel to the sliding tongue arm axis where possible (see installation tips above). This way, the X axis is parallel to the gauge body.

Example of the initial reference frame after a rotation movement:

Illustrative diagram – movement amplified for clarity

Calculating movement on the Y axis

The movement value along the Y axis corresponds approximately to the difference between two R vernier readings, multiplied by 3.3.

Example:

– Reading 1 of R = 49.9 mm

– Reading 2 of R = 49.4 mm

– Difference R2 − R1 = 49.4 − 49.9 = −0.5 mm

– Movement along Y axis = −0.5 × 3.3 = −1.65 mm

Calculating movement on the X axis

Movement along the X axis simply corresponds to the difference in the T vernier readings. Rotation causes a negligible variation in X: a change of 1/10th of a mm on the Y axis corresponds to a difference of 0.5 micrometres on the X axis (i.e. 0.0005 mm).

Download the Saugnac.app to track your measurements

The Saugnac web application is completely free with no limitations and is available on PC and smartphone at https://saugnac.app. It allows you to:

– identify each gauge and its readings using its unique QR code

– record readings and automatically calculate the X and Y axis variation for the G6 gauge based on T and R values

– retrieve temperature and humidity data via geolocation

– calculate readings with thermal expansion correction based on temperature

– collaborate with multiple users on the same gauge

– manage alert thresholds

– organise gauges by location and view them on a map

– export data in Excel format

– display automatic graphs

– share data with other users without an account

– access the application from your PC or smartphone

– add readings offline without an internet connection

Find out more about the Saugnac application.