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On Mon, 3 Aug 1998 RLatulip@ao*.co* wrote: > In a message dated 8/3/98, 1:48:19 AM, heseltine@ea*.ne* writes: > > <<advantage as breathing a fixed pO2 mixed on the fly>> > > Tell me you really don't expect your electronics to monitor and maintain a > constant PO2 at all times??? > Of course we do. That's what the electronics are there for. > I stopped using an Air Integrated computer when it failed in the middle of a > cave dive, I am just glad I wasn't depending on it to monitor my PO2 level. > And the unit in question failed on several different occassions for different > reasons. That's why the concept of redundancy is used in electronic rebreathers. And again, even if all the electronics fail, you can then fly it in a very efficient semi-closed mode. > Tell me what does a 20 degree instant temperature change do to the sensor > BIAS??? Absolutely nothing. I just did a couple of dives where the temp was about 68-70 on the surface, and 42-ish on the bottom. The key is that the o2 sensors are positioned at the exit port of the scrubber, which keeps them warm, and the scrubber itself is insulated from abient temp with a gas plenum. Plus, don't forget, the sensors themselves have a thermistor that compensates for temperature variances from below 0C to +70C. They have to have that, because loop temperature frequently varies by +20-40 deg.F over ambient, and usually operates around 100 deg F. Alot of genuine engineers have worked on this stuff for many years - trying to use sensor temp variance as a jousting point is laughably ignorant. -Will > >>Mir 23 Status Report > >>Mission Control Center -- Korolev > >>Friday, April 11, 1997 > > >>http://shuttle-mir.nasa.gov/shuttle-mir/mir23/status/week6/missrpt.html > > >>While this work was going on, Lazutkin started work on repairing the > Elektron >>oxygen-generating system in Kvant-2. Although this unit was > activated briefly >>several times, it shut off automatically. Ground personnel > believe this is due to a >>faulty sensor in the control unit, which will be > replaced by cannibalizing the same >>unit from the inoperative Elektron > located in the Kvant-1. A new Elektron unit will >>be installed in Kvant-1 > after it is brought to the Mir by the Atlantis astronauts in >>mid-May. . > > What part do you plan on cannibalizing during your ascent/deco??? > > >>Events from 2.5 minutes before the accident to about 5 minutes after. Times > given >>are in Ground Elapsed Time (G.E.T.), that is, the time elapsed since > liftoff of Apollo >>13 on April 11, 1970, at 2:13 PM Eastern Standard Time > (EST). 55:52:00 G.E.T. is >>equal to 10:05 PM EST on April 13, 1970. > > >> http://www.hq.nasa.gov/office/pao/History/Timeline/apollo13chron.html > > >>55:54:43 - Flow rate of oxygen to all three fuel cells begins to decrease. > > >>55:54:45 - Oxygen tank No. 2 pressure reaches maximum value of 1008.3 psia. > > >>55:54:51 - Oxygen tank No. 2 quantity jumps to off-scale high and then > begins to >>drop until the time of telemetry loss, indicating failed sensor. > > >>55:54:52 - Oxygen tank No. 2 temperature sensor reads -151.3 F. > > >>55:54:52.703 - Oxygen tank No. 2 temperature suddenly goes off-scale low, > >>indicating failed sensor. > > >>55:54:52.763 - Last telemetered pressure from oxygen tank No. 2 before > telemetry >>loss is 995.7 psia. > >>................. > > >>55:55:20 - Swigert: "Okay, Houston, we've had a problem here." > > >>55:55:28 - Duke: "This is Houston. Say again please." > > >>55:55:35 - Lovell: "Houston, we've had a problem. We've had a main B bus > >>undervolt." > > >>55:55:42 - Duke: "Roger. Main B undervolt." > > >>55:55:49 - Oxygen tank No. 2 temperature begins steady drop lasting 59 > seconds >>indicating a failed sensor. > > >>55:56:10 - Haise: "Okay. Right now, Houston, the voltage is--is looking > good. And >>we had a pretty large bang associated with the caution and warning > there. And as I >>recall, main B was the one that had an amp spike on it once > before. > > >>55:56:30 - Duke: "Roger, Fred." > > >>55:56:38 - Oxygen tank No. 2 quantity becomes erratic for 69 seconds before > >>assuming an off-scale low state, indicating a failed sensor. > > Who you gonna call when things go bang and your sensor fails! > > Ray LaTulippe > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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