Mathematical Analysis of an Ideal ZED

[mondrasek]

The graphical presentation of data is easy with spreadsheets.

And the graphical functions to visualize data are one that I use the most.  Also, exporting Servo Motor traces from an O-scope via a .cvs file allows for quickly solving for Duty Cycle, which is something else I do frequently.  But I am not the "Jack of all trades" that some of you are.  Call me lazy, but I have to know how to operate so many software programs and hardware platforms that I try to limit my knowledge of each to what I need to do so I can move on to the next task.  It is a rare occasion that I delve deeper than that and only because one of those tools has piqued my interest.  Learning more about Excel just for this simple Analysis was something I did not consider of value.

I have utilized the services of Analysts and Software Engineers where I work when a specific spreadsheet or VBA app appears to be a useful tool to eliminate redundant accounting or calculation activities that I and coworkers are found to be performing.  But I do utilize the talents of those other team members rather than learn the skill myself based on a time and value proposition case by case.

[MarkE]

To be honest, it is because spreadsheet programs were not introduced (to me at least) before I finished my University studies and I have never been formally trained or taken the time to learn more than the basic capabilities of Excel.  I can write basic math functions in Excel, but I do not know how to label cells, reference anything on different tab, or anything involving scripting!  So math functions that I would write all reference cell locations which makes it very difficult to follow and debug.

Google "named ranges, Excel".  Unless you want to write a computer program, there is no need to do so in Excel.  Excel is at its heart a place that one can stuff equations.  Named ranges (cells are ranges of one cell) allow you to get past 1989 and use names to refer to values in a spreadsheet instead of $a$12 etc.

When I started the Analysis it was with the 2-layer system.  I can run those numbers on a calculator much quicker than building a spreadsheet.  However, when I started thee 3-layer I did consider attempting to calculate in the spreadsheet.  But since the 3-layer used the same inner 2-layer, those values mostly remained the same.  So I continued with the manual method that I had employed earlier, even though State 3 does become a mind numbing PITA at this point (for me at least).

Whatever process you followed you have not documented it well enough to audit.  I am not a mind reader.  You learned in university that if you don't show your work, your work is rightly rejected.  The very first calculated value I encountered in your spreadsheet is inconsistent with your verbal descriptions and drawings.  That's a full stop for me.  Take care of your responsibility to assemble and show your work and we can figure out where you went wrong.  It is inescapable that you have done something that violates First Principles either in your model, your interpretation of your model, your calculations or your transcription.

I think I have an answer for this, and I apologize for not noticing that I did this or I would have pointed it out.  The Volume calculations for the air neglect the volume directly above the pod and riser top surfaces since those never change.  So the Volume of the air is only calculated as the "U" shape section, very similar to the "U" shape of the water volumes sections.

In the example you show, please subtract the pi * r²*ht Volume of air above the pod which is pi*1cm²*.1cm = .3141592654cm³.  Our numbers are then the same.

I am not going to try and second guess work that you do not present.  If you want me to audit your work, then you need to show your work.  You can write out the equations you used, or you can enter them into something like Excel, or do whatever else you need to actually show the process you relied upon to get your errant results.  I have attached a copy of your spreadsheet with a work sheet added that separated the numerical values from the text, and named all the identifiable numerical cells.  If you like you can use that as a starting point.

[MarkE]

Really, the spreadsheet is what "computers are for." 

You can do so much with spreadsheets. Properly set up spreadsheets can handle all your household, tax, budget, automobile records,  financial planning, numbers racket, scientific data analysis, anything involving data sets and interrelationships between data. A little time spent fooling around with and learning spreadsheet functionality and use is well worth the effort if you do any number crunching in your life at all.

I consider my own spreadsheet skills to be very basic, but I couldn't do without them. The graphical presentation of data is easy with spreadsheets.  The existence of spreadsheet programs like LibreOffice Calc or MS Excel entirely justifies the existence of the personal computer. If a computer could do nothing but spreadsheets it would still be necessary to own one for that reason alone.

VisiCalc is what got interest in personal computers beyond geeks.

[mondrasek]

Google "named ranges, Excel".  Unless you want to write a computer program, there is no need to do so in Excel.  Excel is at its heart a place that one can stuff equations.  Named ranges (cells are ranges of one cell) allow you to get past 1989 and use names to refer to values in a spreadsheet instead of $a$12 etc. Whatever process you followed you have not documented it well enough to audit.  I am not a mind reader.  You learned in university that if you don't show your work, your work is rightly rejected.  The very first calculated value I encountered in your spreadsheet is inconsistent with your verbal descriptions and drawings.  That's a full stop for me.  Take care of your responsibility to assemble and show your work and we can figure out where you went wrong.  It is inescapable that you have done something that violates First Principles either in your model, your interpretation of your model, your calculations or your transcription.I am not going to try and second guess work that you do not present.  If you want me to audit your work, then you need to show your work.  You can write out the equations you used, or you can enter them into something like Excel, or do whatever else you need to actually show the process you relied upon to get your errant results.  I have attached a copy of your spreadsheet with a work sheet added that separated the numerical values from the text, and named all the identifiable numerical cells.  If you like you can use that as a starting point.

MarkE, I am sorry you feel that way.  I have said that my calculations and methods lead to an Analysis that equaled the results of your own up through State 2.  I have then outlined, with all equations, the process that I used to Analyze the change from State 2 to State 3 and the final State 3.  I see no point in stepping backwards or in presenting anything in a different format.

I would be happy to explain any single step along the way if you have specific questions.

[MarkE]

MarkE, I am sorry you feel that way.  I have said that my calculations and methods lead to an Analysis that equaled the results of your own up through State 2.  I have then outlined, with all equations, the process that I used to Analyze the change from State 2 to State 3 and the final State 3.  I see no point in stepping backwards or in presenting anything in a different format.

I would be happy to explain any single step along the way if you have specific questions.

I beg to differ.  You have about 75 cells in your spreadsheet that just have values in them.  Where are the 75 corresponding equations?  We already know that the very first non-zero value in your spreadsheet was not the result of the model you represented.  Obviously, you have some issues auditing your own work to insure that it represents what you intended.  If you think others should try and read your mind, well then good luck to you.  If you won't be bothered to show your work then you have no business asking anyone to audit what you refuse to show.