Remember:
P1V1/T1 = P2V2/T2
Even though this uses absolute pressure and temperature, temperature is a factor, as is altitude with the capillary gauge. Somewhere I have an altitude correction table from a high altitude diving conference I attended in about 1975. Some people used to dive capillary gauges at altitude and in cold water because they read deeper than the actual depth, thereby becoming a safety factor. This was because the air at altitude is less dense, and compresses more as the diver descends; the air column when chilled also has a bit less volume, and therefore the gauge will read deeper than the actual depth. One of those divers who used these gauges for a safety factor was me.
Concerning the Sportsways SPG, I see no reason not to use it, but would check it against a digital computer to see if it is reading accurately. Even if it is not, it will be consistently off and if known, you can still use it.
SeaRat
PS--I found the Altitude Corrections Tables in my computer. Note that an oil-filled gauge will read shallow, whereas the capillary gauge will read deep. For instance, at 4000 feet (Clear Lake, in the Oregon Cascades), you need to add 4.7 feet to an oil-filled gauge, whereas the capillary gauge will read deeper and you need to multiply the depth reading by 0.887 to get the actual depth for the dive. If using tables, the difference in the oil-filled gauge's depth reading could cause a misreading of your decompression tables. Also, the "Theoretical Depth at Altitude," the Cross Tables, show that at an actual depth of 90 feet, the theoretical depth (because of pressure changes) that you should use when calculating decompression at 4000 feet is 104 feet. Add to this the oil-filled gauge reading shallow, and a diver could get into problems.
PS2--Here's an older photo from about 1973 of me in Clear Lake by Bruce Higgins, showing why we enjoy diving that lake.
P1V1/T1 = P2V2/T2
Even though this uses absolute pressure and temperature, temperature is a factor, as is altitude with the capillary gauge. Somewhere I have an altitude correction table from a high altitude diving conference I attended in about 1975. Some people used to dive capillary gauges at altitude and in cold water because they read deeper than the actual depth, thereby becoming a safety factor. This was because the air at altitude is less dense, and compresses more as the diver descends; the air column when chilled also has a bit less volume, and therefore the gauge will read deeper than the actual depth. One of those divers who used these gauges for a safety factor was me.
Concerning the Sportsways SPG, I see no reason not to use it, but would check it against a digital computer to see if it is reading accurately. Even if it is not, it will be consistently off and if known, you can still use it.
SeaRat
PS--I found the Altitude Corrections Tables in my computer. Note that an oil-filled gauge will read shallow, whereas the capillary gauge will read deep. For instance, at 4000 feet (Clear Lake, in the Oregon Cascades), you need to add 4.7 feet to an oil-filled gauge, whereas the capillary gauge will read deeper and you need to multiply the depth reading by 0.887 to get the actual depth for the dive. If using tables, the difference in the oil-filled gauge's depth reading could cause a misreading of your decompression tables. Also, the "Theoretical Depth at Altitude," the Cross Tables, show that at an actual depth of 90 feet, the theoretical depth (because of pressure changes) that you should use when calculating decompression at 4000 feet is 104 feet. Add to this the oil-filled gauge reading shallow, and a diver could get into problems.
PS2--Here's an older photo from about 1973 of me in Clear Lake by Bruce Higgins, showing why we enjoy diving that lake.
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