Here's a close-up of the PO2 display, which is nothing but a cheap plastic box containing a 9v battery, a switch, and a DPM125 200mV LCD display. I filled the box with a re-enterable urethane potting compound, and used a waterproof switch cover from APM HexSeal, which is theoretically rated to 10,000PSI or something rediculous like that. The re-enterable urethane seemed like a good idea at the time, but when the battery eventually died, trying to dig it out of the potting compound proved impossible, and I ended up cracking open the cheap plastic box and making a new one.

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