SICK GRTE18S-P234Z Photoelectric sensors. SICK GRTE18S-P234Z is a photoelectric sensors in the GR18 family. SICK identifies this exact configuration as manufacturer article 1059487. The official technical record specifies Functional principle: Photoelectric proximity sensor; Functional principle detail: Energetic; Dimensions (W x H x D): 18 mm x 18 mm x 38.1 mm; Housing design (light emission): Cylindrical; Thread diameter (housing): M18 x 1; Optical axis: Axial, fully flush. The linked SICK data sheet is specific to GRTE18S-P234Z.