Description
Plus Tell-Tale
The Avongard Plus Tell-Tale is a precision gauge, consisting of two plates which overlap for a part of their length.
The bottom plate is calibrated in millimetres and the top plate is transparent and marked with a hairline cursor in the form of a cross.
Avongard Plus Tell-Tales can be used to monitor 2D (horizontal or vertical) movement across a crack on a flat surface.
The Plus offers two upgrades to the Standard design:
- Rather than presetting the two measuring plates together at zero with tape, the plus uses four small pegs, which ensure alignment during installation and then removed during monitoring.
- The plus also provides measuring flats (spigots), which allow accurate readings to be taken with calipers during monitoring.
Features:
- Tell-Tales are manufactured in the UK, in compliance with ISO 9001, from tough and durable vandal resistant polycarbonate.
- Application: Monitoring of crack displacement on concrete or walled structures.
- Range: ± 25 mm horizontal and ± 10 mm vertical.
- Accuracy: ±1.0 mm on scale.
- Temperature: -40 to +80 degrees C.
- Coefficient of thermal expansion is 6.8 x 10-5 cm/cm per degree C
- Weather resistant.
Each Plus Tell-Tale is supplied with:
- 1x AF11 – set of Fixing Screws (4 screws + 4 plugs)
- Installation instructions.
- Crack Monitoring Record Sheet. Aditional sheets available for free. Download here.
1. Initial Measurement
Use the AW11 Crack Width Gauge to measure and record crack width before monitoring. The AW11 is sold separately.
2. Fixing the Tell-Tale
Clean the surface and fix the Tell-Tale across the crack using the supplied screws and plugs and/or AE14 Araldite adhesive (not included but available as accessory).
3. Commissioning the Tell-Tale
After fixing the unit on both sides with the screws and/or adhesive, the four pegs need to be removed.
4. Monitoring Cracks to +/- 1.0 mm accuracy
As the crack opens, or closes, the cursor moves relative to the calibrated scale. The opening or closing of the crack is then recorded on the crack record sheet supplied.
5. Monitoring Cracks to +/- 0.1 mm accuracy (with a caliper)
For more accurate monitoring, calipers can be used to measure the distances between the spigots. The distance between the spigots is then recorded on the crack record sheet supplied.
The calipers are available for sell as a separated accesory.
It is also recommended to record the ambient temperature as seasonal changes may affect the evaluated structure.
For a better understanding on cracking causes and structural behaviour, we highly recommend the book “Guide to subsidence”, also available in our store.
