The acoustic signal is transmitted over an air gap to a non-contact receiver at the other end of the spindle. The spiral cable type works on the same non-contact principle but the telescopic slide tube is replaced with a spiral cable.
The in-spindle sensor is useful for OEMs manufacturing internal/ external grinding spindles or rotary diamond dressers. Schmitt are also able to provide mounting kits for end-user applications where a spindle bore is available. Mounting an AE sensor in this way gives a more direct signal and increased sensitivity.