NAUI Master Scuba Diver 18 Diving Equipment indicator needle. Some diaphragm gauges are adjustable for use at altitude. An electronic depth gauge is frequently called a digital depth gauge. This gauge operates in the same way as an electronic cylinder pressure gauge, but at lower pressures. Digital depth gauges can be sensitive to temperature variations and require batteries for operation. A digital depth gauge can also be difficult to read in low light levels unless the instrument has a backlit screen feature. These gauges are extremely accurate and easy to read without error. Other features, such as a maximum depth indicator or an ascent rate indicator, may be easily incorporated. Depth gauges measure pressure, and are usually marked in feet or meters of sea water, so an adjustment must be made for fresh water and altitude diving. Gauges may be subject to damage if exposed to reduced pressures when flying and should be transported inside pressure-tight containers or inside a pressurized cabin in an aircraft. Commercial airline cabin “altitude” can be as high as 2000-2500 m (6500-8000 ft), which can damage some gauges. A desirable feature of a depth gauge is a maximum depth indicator, which retains the maximum depth reached during a dive. The indicator can be mechanical on analog gauges or electronic on digital gauges. The maximum depth indicator resets automatically on digital gauges, but you must remember to manually reset the indicator on mechanical gauges. Accuracy for mechanical gauges is typically ±1% for the first half of the depth scale and ±2% for the second half of the scale. This accuracy is further affected by age, abuse, and reduced ambient pressure exposures. The accuracy of electronic depth gauges is ±30 cm (1ft.). All depth gauges must be calibrated annual ly, either by means of a marked rope for comparison or with the use of a “pressure pot” (a small pressure chamber) at your local NAUI Dive Center. Interim checks can be performed by comparing your depth gauge to a capillary gauge at shallow depths. Depth gauges should be treated with care. Prevent shock and low pressure damage. Avoid leaving gauges, especially oil-filled gauges, in the sun because heat will Rubber Diaphragm Sealed Bourdon Tube Gauge Rigid Case Water Pressure Capillary Gauge Water Pressure Inlet and Filter Water Pressure Open Bourdon Tube Gauge Oil-filled Tube Bourdon Tube 10 Air Bubbles FIGURE 1-14. TYPES OF DEPTH GAUGES
20047TC
To see the actual publication please follow the link above