Author Archives: mathscinotes

Parabolas and Avalanche Photodiodes

Posted on 6-January-2013 by mathscinotes

During a meeting recently, a vendor was discussing the need for performing production calibration testing that required fitting a parabola to the data from an optical sensor called an Avalanche PhotoDiode (APD) (Figure 1). I recalled this comment while reviewing a test report this morning where I saw a parabola appear in an APD test report from an optical physicist in my group. I realized that our physicist and this vendor were working in related areas. It was an excellent test report that covered both the theoretical and experimental aspects of the subject. It also seemed like a good topic for this blog. Continue reading →

Posted in Electronics | Comments Off on Parabolas and Avalanche Photodiodes

Battery Failure Rates and Continuously-Compounded Interest

Posted on 2-January-2013 by mathscinotes

While performing some routine reliability analysis, I noticed that there is a similarity between battery aging and continuously-compounded interest calculations. I had not noticed this similarity before, and I thought I would document it here.

Figure 1 shows a common lead-acid battery. This chemistry is my focus in this post. Other chemistries will behave similarly, but the constants involved will differ. I will be assuming that the failure rate of the battery is described by the Arrhenius equation. Continue reading →

Posted in Batteries, Electronics | 1 Comment

Lead Acid Battery Life Math

Posted on 24-December-2012 by mathscinotes

Quote of the Day The key to effective goal-setting is being realistic about what you can accomplish. — Andrea Woroch Introduction It is difficult to dig trenches for fiber optic cable in many parts of the US and Canada during … Continue reading →

Posted in Batteries, Electronics | 2 Comments

Battery Charge Capacity and Energy Math

Posted on 16-December-2012 by mathscinotes

Introduction I am doing some requirements analysis work on backup power systems for GPON ONTs. As part of this work, I need to perform an evaluation of a number of batteries for charge capacity and energy. As part of this … Continue reading →

Posted in Batteries, Electronics | 4 Comments

Outdoor Enclosure Temperature Profile Math

Posted on 9-December-2012 by mathscinotes

Introduction We build products that mount on the outside of homes -- homes that can be anywhere in the world. This means that the temperatures can be brutally cold (e.g. -46 °C in Bemidji, MN) or brutally hot (e.g. 49 … Continue reading →

Posted in General Science | 6 Comments

Torpedo Data Computer Video

Posted on 9-December-2012 by mathscinotes

I am a fan of both naval history and the history of computing machines. I just saw a great video on the Torpedo Data Computer (TDC) that have I include here. The TDC was one of the last examples of … Continue reading →

Posted in Electronics, History of Science and Technology | 1 Comment

Network Cable Math

Posted on 6-December-2012 by mathscinotes

Introduction Today I'm going to be discussing ethernet cables and if you've been reading this blog for a while, you know I'm no stranger to ethernet problems. I work with it quite a lot at work so I'm familiar with … Continue reading →

Posted in Electronics | 7 Comments

Crest Factors for QAM Signals

Posted on 26-November-2012 by mathscinotes

Quote of the Day If you want to succeed you should strike out on new paths, rather than travel the worn paths of accepted success. — John D. Rockefeller Introduction I need to do a quick calculation of the Crest … Continue reading →

Posted in Electronics | 22 Comments

Trapezoids Better Than Sinusoids?

Posted on 22-November-2012 by mathscinotes

Sinusoids hold a revered place in electrical engineering -- they should. However, I do encounter quite a few trapezoids in telecom power systems. During a meeting the other day, I was asked "Why do we use trapezoidal waveforms for Alternating Current (AC) signals like ringer voltages and remote power systems." It was a good question. I have written about the trapezoidal waveform before, but I have never explained why the trapezoid is used so frequently. Continue reading →

Posted in Electronics | 7 Comments

Design Review of Four Transistor Current Source

Posted on 20-November-2012 by mathscinotes

One of the engineer's in my group asked if I had any information on how a four transistor current source works. I decided that to pull together a quick Mathcad worksheet. The Wikipedia refers to this current source configuration as … Continue reading →

Posted in Electronics | 3 Comments