Rebreather World - View Single Post

silent running · 13th November 2007, 18:57

Quote: (Originally Posted by deepreef)

Now, diver begins descent. As ambient pressure increases, the system continues to validate the primary sensor with air and oxygen until reaching a depth of 6m. Each test compares three values:

1) FO2 (fraction of oxygen)
2) Pamb (ambient pressure)
3) PO2 (calibrated mV reading from the primary O2 sensor)

If ANY ONE of these values is not right, the answer is wrong, and the system is not confident it knows the PO2 anymore. So...as long as it's air (FO2=.21) or Oxygen (FO2=1.0), and as as long as the depth sensor is reading the correct Pamb, and as long as the O2 sensor is putting out the correct mV for the PO2, the system allows the diver to continue the dive. But if any of these values are not right (i.e., Dil is not really air, depth sensor is not working properly, or O2 sensor is not working properly), then the test fails, and the diver is sent to the surface on OC.

The key here is that the test is performed over the course of the first 6m (20ft) of descent. Rich

Hi Rich, (or Nigel), it occured to me that in order for the unit to do it's inwater checks to 6M, the diver would probably have to do a very slow descent and stop at 6M for a period. Is this right, and if so, what happens if the diver has to do a fast decsent, say in a current where getting down quickly can mean the difference bewtween finding the wreck/reef and being blown out into the blue? Would the unit force you to bail to OC if the descent was too fast for the auto val system to do it's checks? Thanks, -Andy

13th November 2007, 18:57	#186 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,873	Re: Cis Lunar Mk 6 Quote: (Originally Posted by deepreef) Now, diver begins descent. As ambient pressure increases, the system continues to validate the primary sensor with air and oxygen until reaching a depth of 6m. Each test compares three values: 1) FO2 (fraction of oxygen) 2) Pamb (ambient pressure) 3) PO2 (calibrated mV reading from the primary O2 sensor) If ANY ONE of these values is not right, the answer is wrong, and the system is not confident it knows the PO2 anymore. So...as long as it's air (FO2=.21) or Oxygen (FO2=1.0), and as as long as the depth sensor is reading the correct Pamb, and as long as the O2 sensor is putting out the correct mV for the PO2, the system allows the diver to continue the dive. But if any of these values are not right (i.e., Dil is not really air, depth sensor is not working properly, or O2 sensor is not working properly), then the test fails, and the diver is sent to the surface on OC. The key here is that the test is performed over the course of the first 6m (20ft) of descent. Rich Hi Rich, (or Nigel), it occured to me that in order for the unit to do it's inwater checks to 6M, the diver would probably have to do a very slow descent and stop at 6M for a period. Is this right, and if so, what happens if the diver has to do a fast decsent, say in a current where getting down quickly can mean the difference bewtween finding the wreck/reef and being blown out into the blue? Would the unit force you to bail to OC if the descent was too fast for the auto val system to do it's checks? Thanks, -Andy
(Offline)