Strain Gage Encapsulation?
A quick look in the M-M strain gage catalog shows several EA, N2A and N2K series gage “options” that include a cover (encapsulation) of the strain gage grid. These options include E, LE, SE, W, E2, and E3. Encapsulation is also standard on CEA, L2A, C2A, WA, SA, WK, SK, SD and WD gage series.
Just what are the advantages/disadvantages of grid encapsulation? The biggest advantage of grid encapsulation is protection of the thin sensing foil used in the grid. During gage installation encapsulation protects against fingerprints, tool scratches and perhaps even solder splash. After gage installation the encapsulation provides a degree of environmental protection which will improve gage resistance stability over time. As a result, grid encapsulation is the most popular gage “option."
Disadvantages of grid encapsulation include doubling of the initial resistance tolerance compared to open face gages of the same type and a minor price adder. On thin or low modulus specimens encapsulated gages will add more reinforcement than open face types.