IEEE Consultants' Network of Long Island

A Torn Retina - John Dunn, Consultant, Ambertec, P.E., P.C.

I developed a torn retina in my right eye in February 2001. I first noticed the visual abnormalities of that damage while coming into the house after a five-hour nighttime drive from Massachusetts through lots of adverse winter weather.

I seemed to see horizontal lightning strikes way up high and way down low in my field of vision and there was a very substantial increase in the number of "floaters" right in the middle.

Some years later, those floaters were imaged by my ophthalmologist:  

Capacitively Loaded Op-Amps - John Dunn, Consultant, Ambertec, P.E., P.C.

Op-amp stability or instability when driving capacitive loads is sometimes an area of difficulty.

The test fixture sketched below was used to examine the transient responses of several common op-amps when feeding a moderate (380 pF) load capacitance.  

 

The test results for a small variety of devices constitute a cautionary tale:

The Neon Lamps - John Dunn, Consultant, Ambertec, P.E., P.C.

The story you are about to read is true. Only the names have been omitted to spare somebody the embarrassment. 

A whole array of neon lamps were provided at the bottoms of panels in a rack of military electronic equipment. Each lamp was supposed to turn on and off at the action of an SPST switch.

The circuit and the physical arrangement that were used are sketched here.

Diode Dynamic Impedance - John Dunn, Consultant, Ambertec, P.E., P.C.

A diode can be used as a variable attenuator element based on variability of the diode's dynamic impedance versus its bias. An estimate of that dynamic impedance can be found from the basic diode equation as follows: 

 
 

Old Dog Learns New Tricks - Dick LaRosa

Better late than never, I learned to enlarge plots of sea surface height (SSH) in the Gulf of Mexico (GoM) on the monitor screen by hitting Ctrl and + multiple times. Now I can actually see two clockwise eddies trapped in the Loop Current (LC) running into each other and piling up water. This destroys some of their individual vorticities, creates SSH as high as 150 cm where their respective peripheral velocities collide. This creates a steep ramp of SSH whose downhill direction is pointed in the downstream direction toward Florida. The ramp is always located on the north coast of Cuba near Los Orroyos at the west end close to where the two capes are  joined to the wider part of the island.

I also learned to hit Prt Scr to copy the expanded screen into the Clipboard so that I can paste it into Word. I don't do this too often because it generates too many printouts when I watch the annihilation events at one-day intervals. Sometimes the SSH labels obscure the SSH contours and I have to go back-and-forth between annotated and un-annotated SSH contours, as well as view successive days to follow the progress of a particular feature. The selection page of the website has a strange appearance when it is expanded, but I have become quite familiar with it and can navigate easily.

CLATHRATE/HYDRATE/CH4/CO2/FRACKING??--Carl Schwab

Recent interest in fracking (fracturing) shale layers to release methane (CH4) and oil is stirring quite a controversy. I want to make some comments that may shed some light and reduce the smoke a little<G>. There are a number of anecdotal stories about burning ice, water wells that gush bubbling water and well water that fizzes.

Methane gas, CH4, (or carbon dioxide, CO2) rather easily bound to clusters of water molecules in a few different ways. In the middle US states, frequently by sufficient relatively low pressure, gaseous CH4 or CO2 are readily absorbed in to cool water such as one could pump from say a 120 foot deep well for drinking water. When this water is brought to the surface the CH4 or CO2 will bubble off and go into the atmosphere and is perfectly drinkable. As a fact well pumps have been designed to separate the CH4 or CO2 at the well bottom and let the CH4 rise (lighter than air) and vent harmlessly. They are careful NOT to make the well top airtight. The CO2 being heavier than air will sink to the bottom of the well shaft. This is NOT from hydration.

Flashlight Batteries and Bulbs - John Dunn, Consultant, Ambertec, P.E., P.C.

It's a small thing perhaps that so many flashlights become unreliable with use, but it's been a pet peeve of mine for quite some time.

Many flashlights depend on the tip of the bulb to make contact with the positive end of the upper flashlight cell as sketched below on the left. This works okay for a while, but eventually, the metal of the bulb's tip deforms by flattening out while the positive tip of the flashlight cell also deforms by becoming concave as sketched below on the right.

Then the flashlight doesn't stay lit as I hold it. I have to shake a little it to get light or I have to twist the light bezel back and forth a little bit.

Root Mean Square versus Root Sum Square - John Dunn, Consultant, Ambertec, P.E., P.C.

Consider some repetitive voltage waveform applied across a resistance of R:

At time T1, we have voltage E1 across resistance R which yields a power of E1² / R.

At time T2, we have voltage E2 across resistance R which yields a power of E2² / R.

At time T3, we have voltage E3 across resistance R which yields a power of E3² / R.

.... and so forth and so forth and .....

At time Tn, we have voltage En across resistance R which yields a power of En² / R.

First consider the root-mean-square (RMS) of thee voltages as follows:

Train Whistles - John Dunn, Consultant, Ambertec, P.E., P.C.

I was listening to an interview on Public Radio earlier today where the topic was acoustic environments,

In the course of that dialog, a comment about train whistles was offered which I have not been able to independently confirm, but which very much caught my attention.

The interviewee stated that Canadian train whistles are required by law to be triple-toned as an E-flat minor triad. American train whistles can be single-toned, but Canadian whistles must meet the more demanding requirement.  

I just had to check this out.  

Some Number Stuff - John Dunn, Consultant, Ambertec, P.E., P.C.

Divisibility:

If any number ends in zero or five, then that number itself is evenly divisible by five with no remainder which is pretty much obvious.

What is somewhat less obvious however is that If the sum of the digits of any number is evenly divisible by three with no remainder, then the number itself is evenly divisible by three with no remainder.

For example, in the number 9638184, the sum of the digits is 39 which is evenly divisible by three with no remainder which means that the number 9638184 is itself is evenly divisible by three with no remainder.

Thus, 9638184 / 3 = 3212728 exactly with no remainder.