one end. The tubing is marked with numbers that correspond to your depth. As you descend in the water, water enters the tube and compresses the air inside. You read your depth by looking at the air and water interface inside the tube. A capillary tube is very useful at shallow depths (above 12 meters or 40 feet), but is not recommended for deeper depths, as the scale size becomes too small for accurate readings. A Bourdon tube uses pressure to straighten a curved metal tube. Bourdon tubes can be open or closed, although open tubes are rarely seen today. The closed tube is filled with air and is encased in a housing filled with oil. The pressure from the surrounding water is Chapter 2- Diving Equipment transmitted through a flexible part of the housing to the oil and then to the tube. The tube is attached to a linkage and needle and as the pressure opens the tube, the needle moves to show your depth. Bourdon tubes measure depth reasonably accurately. A diaphragm mechanism uses a metal diaphragm, which is attached to a linkage. The linkage is attached to a needle. As the pressure increases on the diaphragm, the needle moves to show your depth. Diaphragm gauges can often be adjusted for their zero point. Electronic depth gauges are part of all dive computers and most electronic dive timers. An electronic depth gauge measures your depth using transducers, and then displays the depth digitally. Electronic depth gauges are extremely accurate and reliable. You must have a means of recording the deepest depth you reach on a dive. Capillary gauges do not have a means of recording your deepest depth so you must remember to record it on a slate during your dive. Bourdon tube and diaphragm gauges might have a second needle that is pushed around the gauge by the depth needle attached to the linkage. The second needle stays at your deepest depth while the depth needle keeps showing your current depth. Electronic depth gauges record your maximum depth in their memory and then display the maximum depth when you surface or on demand. Diving Equipment 29 FIGURE 2-27. MOST ELECTRONIC SUBMERSIBLE PRESSURE GAUGES ARE INTEGRATED WITH DIVE COMPUTERS. FIGURE 2-28. A DEPTH GAUGE MEASURES YOUR DEPTH WHEN YOU ARE UNDER WATER. FIGURE 2-26. THE SPG’S INTERNAL MECHANISM.
19116TC
To see the actual publication please follow the link above