Were you taught this math in your entry level CCR class?

[joshk]

How do you know it is correct at 1.0?

Multiply the mV reading at 0.21 by 4.76 to get an expected 1.0 reading. Flush cells with O2 and compare to expected.

 

[KenGordon]

Multiply the mV reading at 0.21 by 4.76 to get an expected 1.0 reading. Flush cells with O2 and compare to expected.

Why is that true?

 

[joshk]

Why is that true?

1/0.21 = 4.76, linearly extrapolate to get an expected reading. What does this have to do with starting an illustrative graph at a different point?

 

[KenGordon]

1/0.21 = 4.76, linearly extrapolate to get an expected reading. What does this have to do with starting an illustrative graph at a different point?

All that assumes that the lines passes through (0, 0). If you don't show that then what are you extrapolating?

 

[joshk]

All that assumes that the lines passes through (0, 0). If you don't show that then what are you extrapolating?

I understand the assumption being made, I'm disagreeing that the assumption needs to be illustrated.

 

[tbone1004]

@KenGordon single cell calibration points do not allow the line to pass through anything but the origin.
Single point calibration is y=mx
Dual point calibration is y=mx+b

 

[Capt Jim Wyatt]

I worked up this spreadsheet a few years ago for my rEvo instructor training class.

I've been offshore driving a dive boat and/or dealing with hurricane damage for several days and have just today been able to "think" about this thread....

Upon opening the spreadsheet you see the table on the left predicts mV readings at 1 bar O2 when the cell read 9.5 mV in air at 1 bar, if the cell is healthy/linear at 1 bar. (I chose 9.5 randomly.)

Cells H3 and H5 are user input data while cells H4, H6 are not user input and H7 is the result. These data will help us predict when cells are not linear if the actual output in mV does not closely match the predicted mV value.

I hope this helps clarify what *I* was trying to demonstrate when I began this thread.

 

[JohnnyC]

I forgot about this thread, but it's a good read and worth reading again. I put together a little spreadsheet when I did my MOD1 and had it in my checklist when building. It's not predictive like Jim's, but it's a decent quick reference and allows for a little extrapolation.

 

[hammet]

I have no idea about rebreathers, but I did major in math and science...
hello? significant digits? anyone?

 

[JohnnyC]

I have no idea about rebreathers, but I did major in math and science...
hello? significant digits? anyone?

Is this a question about everyone limiting their math to 2 decimal places? In the excel sheet I just posted, you can change that in the formatting. Although greater than 2 digits behind the decimal is really more accurate than we require for our purposes.