Editors note: we are republishing comments made by Bob Klauber PhD in the comments section on a previous blog post: https://fairfieldsafemeters.com/2012/06/13/radio-read-water-meters-pose-dangers/
As a physicist and former dynamic systems failure analyst, I offer a cautionary note, which doesn’t seem to have been considered, that goes beyond analysis of electronics alone.
Every object in creation has a natural resonant frequency at which it can be easily excited by very little input (force, pressure, voltage, etc.) A drinking glass, for example, is simply unaffected by sound except when that sound is a perfect pitch (frequency) match of the glass resonant frequency. In that case, the glass is destroyed. Small input under the right conditions can wreak major damage.
The point is that the magnitude of the input (RF wave in our case) is only one factor. A second factor is the biologic resonant frequencies in the molecules, cells, neurons, and systems of our bodies. There are a great many different such frequencies and small electromagnetic input at any one of them could cause significant disruptions.
Perhaps they do not, but without extensive biomedical testing, no one can really know. Companies selling new technologies have a notorious history of avoiding testing whose results they fear may impact product sales, so caution may be in order.
PhD in Engineering Physics
Retired dynamic systems failure expert
Other than signal strength, there are two key factors any safety/failure analyst considers. One is resonant frequency, as noted in my prior message. The second is pulsing.
The argument that the signal pulses are innocuous because they are only on less than 1% of the time is faulty. It is the number of pulses, not their duration, that leads to failure.
Failure from repeated application of force/stress, rather than a steady force, is known as “fatigue”. A good example is a paper clip. Bend it all the way back on itself and it doesn’t break. But bend it back and forth, and after a few cycles, it breaks.
Consider bending the clip for one second every hour. After a half day or so, it breaks. The total time of force application (the “duty cycle”) is way less than 1%. It is the number of pulses, not their duration, that is the killer.
Even more relevant, a steady force of given magnitude will not cause failure, when a far lesser force that pulses will. This is very well known in failure analysis circles. Consider bending the paper clip ½ way repeatedly. It breaks. Bend it all the way and hold it there, and it doesn’t.
BOTTOM LINE: As a general rule, pulsing, regardless of duration and at markedly lower levels, is significantly more damaging than steady input.
EXPOSURE OF USERS: The Neptune meters pulse 180,000 times per month. This would be alarming to any safety/failure expert.
PhD in Engineering Physics
Retired dynamics & fatigue failure expert