Description
Avongard Standard Tell-Tale
The Avongard Standard 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 Standard Tell-Tales can monitor 2D (horizontal or vertical) movement across a crack (or joint) on a flat surface.
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: ± 20 mm horizontal and ± 10 mm vertical.
- Accuracy: ±1.0 mm on scale.
- Temperature: -40 to +80 degrees C.
- The coefficient of thermal expansion is 6.8 x 10-5 cm/cm per degree C
Each Standard Tell-Tale is supplied with:
- 1x AF11 – set of Fixing Screws (4 screws + 4 plugs)
- Installation instructions.
- Crack Monitoring Record Sheet. Additional sheets are 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 accessories).
3. Commissioning the Tell-Tale
After fixing the unit on both sides with the screws and/or adhesive, remove the two pegs to allow free movement between the plates.
4. Monitoring Crack Movement in 2D
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. It is also recommended to record the ambient temperature as seasonal changes may affect the evaluated structure.
For a better understanding of cracking causes and structural behaviour, we recommend the book “Guide to Subsidence”, also available in our store.
