They are similar to wire type strain gauges. Only difference is that, meta foils are used in place of strain gauge wires to form grid pattern. Foil type resistance gauge has a thickness of 0.005 mm. These gauges are manufactured by printing them on a thin sheet of metal alloy with an acid resistant ink and unprinted portion is etched away. Foils provide more surface area, which increases the heat dissipation capacity, so that, they can be used in high temperature area.
Material Used
The metals and alloys used for the foil are,
(a) Constantan (Copper-Nickel al oy),
(b) Nichrome V (Nickel-chrome alloy),
(c) Isoelastic (Ni + Cr + Ma) and
(d) Platinum.
Advantages of Foil Type Bonded Strain Gauge
- It has better thermal stability, even at high temperatures.
- No stress concentration at terminals.
- Can be fabricated in any size.
- Low hysteresis.