Author Archives: mathscinotes

Air Conditioning Load of a Group of People

I was reading an article about HVAC (Heating, Ventilation, and Air Conditioning) calculations in the Journal of Light Construction that had a quote I found interesting. It said that

… 17 extra occupants added more than a half ton of cooling load. Continue reading

 
Posted in Construction, General Mathematics, General Science | Leave a comment

Accelerometer Power Calculation Example

I am working on a product that uses a Bosch BMA253 accelerometer as a motion sensor. This family of products has become a defacto standard for inexpensive motion detection. In this post, I will provide a simple power calculation example along with some empirical data that Bosch provided me. Normally, I would not consider a simple power calculation worth writing about, but the datasheet did not provide a worked example. I also provide an Excel workbook that parameterizes the critical variables. Continue reading

 
Posted in Electronics | Leave a comment

State Casualty Rates During the Vietnam War

My first engineering manager was named Marl Godfrey. He was an excellent manager who also had keen insights into the human condition. These insights made quite an impression on my 22-year old self – I actually kept a notebook of his comments. Some of his most insightful comments were about the US military and the Vietnam War. Marl has grown up in Oklahoma and he had served in Vietnam. He once commented that Oklahoma had very aggressive draft boards, which resulted in Oklahoma having a relatively high death rate during the conflict. I was reminded of this statement when I recently reviewed my quote database. I thought that I should be able to determine how death rates varied by state during the Vietnam War, which is the subject of this post. Continue reading

 
Posted in History Through Spreadsheets | Leave a comment

Liberty Ship Production Data

One WW2 battle that we hear little about was fought by logisticians. Their battle was between what could be produced versus what could be delivered in time to matter.  This point was driven home to me when I heard a WW2 historian say that the US had the manufacturing capacity to produce 150K tanks, but that level of tank production would consume all the US steel and leave nothing to build the ships needed to carry the tanks to the fight. Continue reading

 
Posted in Excel, History Through Spreadsheets, Naval History | 1 Comment

Shotgun Bore Diameter Math

I have been doing some metalwork lately that involves using units of "gauge". You will find the term gauge used in the measurement of wire, metal thickness, and pipe bore diameter. This quaint, but confusing, measurement system is slowly falling out of favor (example, sheet metal thickness gauge). Continue reading

 
Posted in Metrology | 3 Comments

Thanks Team

I have now started on my next employment adventure. I can only say thanks to the wonderful team of people that I leave behind. They created the products that allowed the Fiber-To-The-Home (FTTTH) market to flourish. Tens of millions of FTTH products are now manufactured every year by companies around the world. These products are amazing in that for very low-cost they can contain such diverse technology: high-speed digital electronics, FPGAs, RF video,  telephony, battery backup, and wireless. The team can be proud of what they have done. You succeeded where many others failed. Continue reading

 
Posted in Personal | Leave a comment

Short-Term Solution for Furnace Condensate Freezing Problem

Minnesotan's have endured a cold winter with relatively little snow, a situation that causes the ground to freeze deeper than expected. In northern Minnesota, we plan for 60 inches of frost depth, but this year the frost has gone much deeper. For those cabins with condensing furnaces, this extra frost depth has resulted in many frozen septic lines. This winter, I have frozen both my cabin and garage septic lines. Continue reading

 
Posted in Construction | Leave a comment

Number of Space Travelers

I was watching physicist Michio Kaku on CSPAN last Sunday night talking about his new book The Future of Humanity. I like watching authors speak on CSPAN because they provide an extended interview format for authors. In this interview, the interviewer Brian Lamb mentioned a factoid as part of a question that I thought was worth investigating. Continue reading

 
Posted in Space | Leave a comment

Colonoscopy Notes

I had a colonoscopy yesterday and it was a great learning experience. I am fortunate that the anesthetic they gave me had little effect, and the doctor was open to answering questions from an inquisitive patient. It probably helped that the doctor was a mechanical engineer that decided to go into medicine – we had lots to talk about. I found it funny when he mentioned that he did not like engineering work on optics – of course, much of my life has been spent designing optics. In the course of this doctors daily work, he uses optics all day long. His gear was from Olympus, some of which is manufactured in Brooklyn Park, Minnesota, which near my home. Minnesota is known for its medical technology. Continue reading

 
Posted in General Science | 3 Comments

Estimating Component Junction Temperature Using Psi-JT

An engineer stopped by my cube today and asked a question about how to estimate the junction temperature of a part on a circuit card that may have an over-temperature problem. Using the common thermal resistances (θJA and θJC), he was obtaining nonsensical results. This problem was a good illustration of the difficulties present in estimating Integrated Circuit (IC) junction temperatures using the commonly supplied thermal resistances. Continue reading

 
Posted in Electronics | Leave a comment