The conditions present in resistance welding applications are extremely harsh. In particular, weld slag and weld flash lead to high rates of sensor failure.

Weld slag melts the surface of sensor caps coated with thermoplastic materials. Eventually, enough slag embeds itself in the cap, causing the sensor to lock-on.

The high velocity of weld flash can cause thermoset materials to chip, causing surface pitting and eventual slag buildup that results in sensor failure.