HMP115 probe 1 If using a probe holder, align it to this groove. 2 Plastic sleeve that locks the probe in place when connected to a mechanically compatible host device (for example, RFL100 data logger). Diameter 14 mm (0.55 in) at this point. 3 Attach from this area if using a cable tie. Diameter 12 mm (0.47 in) at this point. 4 Sensor protection filter. Do not attach from this area.