Tri-Tronics Company: Tri-Tronics Company: Low-cost gap probes
Gap Probe(TM) optical blocks from Tri-Tronics Co. (Tampa, FL) are designed to convert any of the company's photoelectric sensors into low-cost slot sensors.
Probes are easily attached onto the sensors using two screws. Applications include label detection liquid level detection edge guiding splice detection and envelope contents verification. Models are available to sense gap depths of 1.5" to 3.5" in widths of 0.21" or 0.31".