This document was last updated on January 22nd, 2021
The FATHOM CCR’s head is where everything comes together and was designed to minimize head space for the lowest possible static loop volume and overall unit footprint. The head is CNC machined from one piece of solid Delrin. Only the threaded cell holders and hose connectors are separate pieces, which allows for easy replacement if the threads get damaged during transport. A 1 lb/0.5 kg stainless steel handle and strike plate are attached to the back of the head to assist with trim and take the brunt of any accidental ceiling contact. It’s also quite useful for lifting the unit and removing the head.
The oxygen sensors are located at nine, eleven, and one o’clock positions when the diver is prone in the water. These positions keep the sensors high and facing downward to avoid water collecting on the cell faces when the diver is in any position other than lying on their back. The unit uses JJ-CCR style sensors with an SMB connector on a hardwired lead. This eliminates unnecessary connections within the head and ensures a new female SMB connector every time a sensor is replaced. There are no batteries or electronics inside the head, only a fully potted splitter/isolation board that allows for two separate cell monitoring devices, such as a handset and a HUD. Only the gold-plated male SMB connectors protrude from the potting, so, once the sensors are removed, the head can be fully submerged in your rinse tank for cleaning.