MTS Axial Extensometers - Manual (Page 58)

Installation 58
Flat specimens
An extensometer can be mounted to a flat specimen with extension
springs using a disk or wireform attachment. When using a wireform
attachment, it is necessary to replace the attachment adapters with knife
edge hold-downs.
Extension Spring Table
Use the following table to determine which extension spring to use for a
specific specimen diameter. Depending on the specimen diameter, you
can select between different spring lengths and specimen contact forces.
The table shows the recommended spring lengths for a specific
specimen diameter and the contact force on the specimen for each
spring length.
Note The recommended contact force is approximately 600 grams.
Two springs can be used for
larger diameter specimens. One spring can be used on
smaller diameter specimens.
The disk attachment is for
narrow, flat specimens.
The wireform attachment is
for wide, flat specimens.