G1 Gauge

126,50 w/o VAT per box 10 units

  • For parallel lip cracks inside and outside
  • Reading the crack with a resolution of 0,1 mm
    Easier to read: the G1+ gauge or E1 crack meter with digital reading
  • Automatic reading and monitoring of measurements with Saugnac.app
  • Simple fixing with self-adhesives supplied or mechanical fixing with pre-drilled holes
  • Can be fixed at an angle with the folding bar supplied
  • Supplied in boxes of 10 gauges with 1 pen and instructions for use

Made in France

Technical specifications

  • Resolution
    0,1 mm
  • Type of monitoring
    One-axis crack evolution monitoring
  • Type of crack
    Vertical, horizontal and corner cracks
  • Use
    Indoor / Outdoor: weatherproof and UV resistant
  • Mounting
    Gluing with the self-adhesives supplied or mechanical fixing with screws (sold separately)
  • Installation conditions with self-adhesive
    Installation temperature: 0°C to 35°C (-10°C acceptable*) . Effective bonding from -40°C to +90°C
    *warm up the stickers for a few seconds in your hands before use
  • Dimensions
    154 mm with folding bar x 40 mm x 3 mm
  • Maximum amplitude
    approx. 20 mm (possible variation between maximum and minimum measurement)
  • Weight
    5.5 g
  • Material
    Impact calendered PVC with UV stabiliser
  • Coefficient of linear expansion
    7.10-5 m/m/°C

How to install the G1 crack monitor?

Two mounting methods are available:

  • Adhesive mounting: Quick and easy installation using the supplied double-sided adhesives. The surface must be smooth, dry and clean to ensure full adhesive contact.
    If necessary, particularly on rough surfaces (e.g., plaster), bonding can be reinforced using a fast-curing epoxy glue (dual-syringe).
  • Mechanical fixing: G1 gauges come pre-drilled with two Ø 4 mm holes, allowing easy screw fixation. The 4 mm diameter is suitable for most common substrates.
    For difficult surfaces (crumbly, dusty, rough, damp), we recommend mechanical fixation to avoid detachment. Sets of 50 screws and wall plugs are available, or a complete mechanical mounting kit including a 4 mm drill bit, screwdriver, and 40 plugs and screws.

Mechanical fastening gauge G1 Mechanical fastening gauge G1

Installation advice

To measure crack progression most effectively, the gauge should be installed where the crack is widest (typically in the middle). The G1 gauge can be mounted on vertical, horizontal or diagonal cracks. It is placed straddling the crack to measure changes in the opening width.

The G1 gauge is made of a flexible material that conforms to irregular, convex or concave surfaces.

G1 crack monitor tip

Mounting tip – vernier positioning: Ideally position the vernier triangle between 10 and 11, with the two speckled bands visible on either side. This centers the sliding arm. Do not try to align the vernier triangle on zero, as this is unnecessary and very difficult. The principle is to measure the difference between two readings: the first reading is taken as the zero reference, regardless of its value.

If the initial crack is narrow and you want to maximise opening detection, you can move the vernier closer to zero.

 

Note: The G1 gauge does not measure movement along the Y-axis. For bi-axial monitoring, use the G6 gauge.

How to measure crack in angle?

New G1 models (from mid-2025 onwards) feature a grooved bending line on the slider, allowing corner mounting without additional accessories.

Corner crack

For earlier models, G1 gauges are supplied with a foldable bracket designed for corner installation. This part has a thin section that guides the fold.

Alternatively, an aluminium angle bracket (sold separately) can be used for corner installation.

Various configurations include:

G1 crackmonitor in angle G1 crackmonitor in angle Mounting the G1 by folding the slider at the grooved fold line (90° corner)
There are some irregularities in the plucking. Installation of a G1 crack monitor with an intermediate plate (sold separately)
Crack monitor G1 fixed in angle A G1 crack monitor is used in an internal vertical corner with an aluminium angle bar fixed with a plug and screw
G1 crack monitor fixed in angle A G1 gauge is used on a crack on the edge of an external corner with an aluminium angle bar

How to protect the G1 crack monitor?

G1 crack monitor protection

G1 gauges installed in public or high-traffic areas (schools, shops, streets…) may be subject to damage (tearing, graffiti, etc.).

To protect the gauge, a UV-resistant protective cover is available. It is installed using the provided drive anchors or self-tapping screws.

In high-risk areas, the removable E1 crackmeter with transparent mounting plates is recommended. After measurement, only the plates remain fixed to the wall, preventing damage to the gauge body.

How to read the G1 crack monitor?

The top scale is graduated in millimetres from 0 to 30 – this is the main measurement scale.

The lower scale is a vernier, allowing readings to the nearest tenth of a millimetre (10 vernier divisions = 9 mm on the main scale).

Reading a measurement
a) Millimeters:
The pointer of the vernier lies between two graduations on the main scale. Example: between 13 and 14. The number of mm corresponds to the graduation to the left of the pointer of the vernier: in this case that is 13 mm.
b) Reading the decimal:
Find the line on the vernier which is exactly aligned to a line on the measurement scale. In this example, graduation 8 on the vernier is in line with graduation 21 on the measurement scale. The decimal reading is thus 8/10th of a mm.
The total reading is therefore 13,8 mm.

✅ You can also use the free Saugnac app to automatically read the gauge.

🔍 For even easier and more precise readings, consider the G1+ gauge (direct reading) or the E1 gauge (digital reading).

Download the Saugnac.app application to monitor your measurements

The free web application Saugnac.app, available on PC and smartphones (https://saugnac.app), offers:

Saugnac application for monitoring crack measurements

– Identification of each gauge and measurement using its unique QR code
Automatic reading of G1, G1.1 and G1.2 gauges
– Storage of measurements in your online space
– Retrieval of temperature and humidity via geolocation
– Measurement adjustment for thermal expansion
Collaborative use with multiple users per gauge
– Alert threshold management
– Gauge classification by site and map geolocation
Excel data export
Automatic graph generation
– Data sharing with others (no account required)
– Offline mode for data input without connection

Find all the explanations on how the application works

Download monitoring Excel file

Saugnac Excel file for monitoring crack measurements In order to facilitate the monitoring of the evolution of the cracks, you can download the Excel file for monitoring the G1 measurements

This user-friendly file allows tracking of up to 10 gauges per site or project by duplicating a sheet for each location.

The file accounts for the thermal expansion coefficient of the gauge body and the sliding arm, automatically adjusting each reading based on the temperature difference from the initial measurement.
If no temperature is recorded, just leave the field blank to disable compensation.

Note that the impact of the expansion coefficient on the G1 gauge measurement is very small (about 9 micrometers every 1°C).

 

 

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