Vintage Uwatec 80m Depth gauge

[hongrace]

I have acquired this depth gauge recently. The dial has to rotate more than a turn to register depth over 30m. At the back of the gauge there are two adjustment screw. One is called "Calibration Screw" and the other "Compression Altitude". What do they do? How do I calibrate this gauge?

Thank you.

 

[duckbill]

Sounds like a Princeton Tectonics Compact, Swiss made. They are one of the most solid gauges to be had. Very nice.

IIRC, you unscrew the Altitude screw and allow the air to equalize within the gauge. Then you reset the needle to zero by turning the Calibration screw. I'm not sure if you close the Altitude screw before or after Calibrating the needle. It probably doesn't matter, just as long as you remember to close it! If you only dive sea level, then set it once and don't worry about it.