millimeters of mercury (mm Hg), inches of water (inches H₂O), or cubic centimeters per minute (CCM). Their functions are self-explanatory. 1. The SUPPLY PRESSURE gauge (9) is a 0 to 3,000 psig gauge and indicates supply cylinder pressure. 2. The REGULATED HIGH PRESSURE gauge (10) is a 0 to 3,000 psig gauge and indicates regulated high pressure. 3. The REGULATED LOW PRESSURE gauge (11) is a 0 to 200 psig gauge and indicates regulated low pressure. 4. The INPUT PRESSURE gauge (27) is a 0 to 160 psig gauge and indicates regulated low pressure. 5. The LOW RANGE ALTM (13) measures chamber altitude pressure and, under some circumstances, suit simulator tank pressure. It measures pressures equivalent to altitudes between 10,000 and 40,000 feet. 6. The HIGH RANGE ALTM (12) measures chamber altitude pressure to indicate the altitude range equivalent to between 30,000 and 150,000 feet. NOTE: Each altimeter incorporates an inner scale, which indicates altitude in mm Hg instead of in feet. 7. The PRESSURE/SUCTION manometer (4) has a range of –12.0 to +26.0 inches H₂0, and measures the amount of differential pressure between piezometer (26) and the altitude chamber, or between the piezometer and the suit simulator tank. It is used during component testing to measure safety pressure and pressure breathing pressures being delivered by the component and to measure suction flows being drawn through the component. 8. The Hg manometer (5) has a range of 0 to 12.0 inches Hg and measures, in inches Hg, the amount of differential pressure between piezometer (26) and the altitude chamber, or between the piezometer and the suit simulator tank. It is used to measure resistance in an item under test. NOTE: The rotameters used on the test stand are of the variable area type, which means they get progressively larger toward the top, allowing more nitrogen to pass around the ball. The point at which the ball stabilizes is known as the point of dynamic balance. Readings are made across the center of the ball. 9. The OVERBOARD LEAKAGE rotame- ter (6) has a range of 20 to 200 CCM (1,000 CCM = 1 lpm) and is vented to ambient. It measures leakage, or bleed, from an item under test. This rotameter is calibrated at 14.7 psig at 70°F (ambient air). 10. The LOW RANGE LEAKAGE rotameter (7) has a range of 20 to 200 CCM, and is enclosed in the low-pressure system. It measures leakage, or bleed, from a component under test through LEAKAGE CONTROL valve (E), or LEAKAGE ON/OFF valve (G). This rotameter is calibrated with nitrogen at 70 psig at 70°F. 11. The HIGH RANGE LEAKAGE ro- tameter (8) has a range of 200 to 2000 CCM. Its function is the same as LOW RANGE LEAK- AGE rotameter (7). This rotameter is calibrated at 70 psig at 70°F. 12. The OUTPUT FLOW manometer (1) has a range of 0 to 12.0 inches H₂0. It indicates the amount of output flow from the item under test. 13. The INPUT FLOW manometer (2) has a range of 0 to 12.0 inches H₂0. It indicates the amount of ambient air flowing into the altitude chamber. 14. The VENT FLOW manometer (L3) has a range of 0 to 12.0 inches H₂0. It indicates the amount of supply pressure or ambient air to the suit simulator tank. TEST STAND CONNECTIONS Several connections are incorporated in the test stand (fig. 11- 1) for supplying and bleeding pressure to and from the system. These connec- tions are: 1. The N₂ INPUT connector (15) is the N₂ supply cylinder connection. NOTE: The SYSTEM BLEED port (16) has been deleted on later configurations of Model 1172AS100 test stands. 2. The SYSTEM BLEED port (16) bleeds pressure from the various systems. 3. The N₂ INPUT connection (18) is provided for components that require inlet pressures. Either regulated high or regulated low pressures can be provided to the connection. The N₂ INPUT tee connection (28), N₂ INPUT PRESSURE gauge (27) and the gauge guard that protects the input pressure gauge are connected to N₂ INPUT connection (18). 11-8