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Sensor check and diluent warning

Posted: Wednesday 8. February 2023, 11:42
by mobu
Hi.
I've done one simulation in my OSTC plus in CCR mode. Data:
Dil NX32
B/O NX30
SP 1.3

I realize a couple of details:

1- At 30m. I have a diluent warning ppO2 1.25. This warning tells me that if I would flush with my diluent now or breathe it OC, the ppO2 value would be too high or too low. Questions:
- How much does this measure have to deviate, from the current established SP 1.3, to get a diluent warning? In this case it deviates 0.05
- How is this value of 1.25 ppO2 Dil calculated? In my calculations it would be ppO2= 0.32*4= 1.28
- In case of B/O ppO2 values also don't match the formula ppO2= FO2 * PT (ATA)

2- In the sensor check selectable information I have a ppO2 Dil 1.25 and a ppO2 O2 3.91. These ishows the possible ppO2 values in case I would flush with the diluent or with O2 at that moment. Question:
- As in the previous case, I don't understand the resulting values. In my calculations it would be ppO2 dil= 0.32*4= 1.28 and ppO2 O2= 1*4= 4

I hope you can solve these doubts.

BR

Re: Sensor check and diluent warning

Posted: Wednesday 8. February 2023, 20:32
by Ralph
Hi,

the DIL warning is given as soon as the gap between the setpoint and the ppO2 of the current pure diluent becomes 0,2 bar or less. At this point, a dil flush will not noticable bring down the measured ppO2 in the loop and thus may confuse the diver, so the alarm is to make the diver aware of this situation. This 0,2 gap is not adjustable but hard-coded in the firmware.

When converting depth in meters to pressure in bar, a conversion factor of 0.09807 is applied (1 m water column = 0.09807 bar) and the current surface pressure is used (instead of the 1 bar you put into your factor of 4). So the values shown in simulation mode are sensitive to your location (altitude) and current weather (high / low pressure). This also applied to the calculated ppO2 when in bail-out, as well as for the what-if ppO2s when flushing with the currrent dil or with pure O2 - it's all based on the above two: conversion factor & surface pressure.

Doubts solved?

BR
Ralph

Re: Sensor check and diluent warning

Posted: Wednesday 8. February 2023, 20:50
by mobu
Hi Ralph,

Thank you very much for the quick answer.
Doubts have been completely resolved.

BR