The finimeter (or pressure gauge) is a manometer. When diving, it measures the pressure of your compressed air cylinder. This is particularly important, so that you can always keep an eye on your air supply and ascend before you run out of air. Besides measuring pressure, more recent models of the pressure gauges combine the functions of the diving computer as well.
Important tip regarding the finimeter
When you acquire such a device, you should absolutely pay attention to what pressure it is approved for. Thereby there are models for 200 and 300 bar pressure. In any case you should choose the one which is appropriate for your compressed air cylinder!
And one more tip: When putting on the equipment always do a test on the diving tank first, by shortly opening the valve. Thereby, the glass on the finimetershould never be placed in the direction of people. The reason is that it can explode, e.g. when it is faulty.
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