How to find a suitable 'constant'

To arrive at a 'constant' which will make the measured numbers come
closer to the calculated **(hm^2/R) **numbers, try the following:

In this example the ** hm^2/R ** values for the four zones were calculated to be as follows:

zone 1 | zone 2 | zone 3 | zone 4 |

0.0025 | 0.0229 | 0.0590 | 0.1109 |

The numbers taken from the 4 zones of the mask used **during testing** gave the following result

zone 1 | zone 2 | zone 3 | zone 4 |

0.152 | 0.172 | 0.209 | 0.260 |

Take the reading from the 3rd 'window' in the mask (zone 3 ) )which is usually the most accurate of the readings you will make. (If you have say 5 zones then take the 4th zone as being the most accurately read measurement.)

So you take the third reading number and subtract the hm^2 number calculated for
the third window which let us say is **0.059 **then subtract it from the reading number three**(0.209)** this gives you a 'constant' of **0.150**
If you now subtract this same number **0.150** from all the readings you will get the following:

zone 1 | zone 2 | zone 3 | zone 4 |

0.0020 | 0.0220 | 0.0590 | 0.1100 |

As long as you subtract the same 'constant' number from each of the readings - you will still maintain the difference of relative spacing between them, but they become easier to compare with the calculated numbers taken from the hm^2/R value for each window.

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