I went through a long thought process over the same thing. I use a Shearwater on it's own with 3-cell monitoring on my CK but it has taken a lot of debating, is a single, reliable unit better than a triple independant system? On the Shearwater it takes one failure to wipe out the system, on the triple system you have to have two failures to get to a point where you
may have to do some sort of counter-measure. Also remember the Shearwater uses a common ground wire which I think is a BIG weakness.
My ideal system would be Shearwater cal'd to one cell and two independant displays on the other two cells. Unfortunately, my Shearwater will not calibrate on one cell, even Bruce couldn't figure it out. My Plan B was to fit the Shearwater on 3 cells with a jetsam display piggybacked on to the cells. I had a kidney modified to let me do it, cable gland on one port for the Shearwater with two blank ports which could have glands fitted.
It's for sale as it's surplus to requirements as I've bought something with a proper secondary
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Can you imagine drifting along in the sea with your mouth open and a load of f***ing plankton going in? You'd like it, would you?
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Azerbaijani Association of Technical Divers Publicity Officer and Goat Wrangler