§ 4 A bit of theory, a bit of history ...
From the point of view of the "application of the rule of the gimlet", the whole variety of counters can be divided into two classes: induction and electronic counters. Single and three-phase, maximum power, the presence of a "stopper" that does not allow you to "unwind" the meter, all the "gadgets" for multi-tariff accounting and remote data transmission, so to speak, "upstream" (yes, now, there are) signs for our "kulibinyh from the big road" much less important than the "class essence" of the deceived device. Why? And because each principle of information collection about the power consumption has its own "birthmarks", which gentlemen electrowealers use. Consider these two classes of instruments in more detail.
Class one. Electromechanical counters of induction type. Such "reptiles" of the world of counters: everything is changing, and they originated in their Mesozoic, they still live and at the same time feel very well and do not plan extinction. Invented by Galileo Ferraris at the end of the XIX century at the dawn of the spread of commercial power grids. Despite the venerable age, and until now are the main (and in rural areas - and generally the only) type of subscriber means of accounting for the power consumed. Complex electronic filling is absent in principle, hence the dignity (low sensitivity to all kinds of electrical impulses, the possibility of assembling and repairing almost "on the knee" with minimal requirements for the qualification of personnel and, consequently, low price), and shortcomings (impossibility of multi-tariff accounting, sensitivity to any influences that disrupt the work of mechanics, inertia that facilitates their "deception").
The principle of operation is the same as for an asynchronous electric motor (well, you understand me): the winding system creates a rotating magnetic field, which unwinds the conductive disk placed in it, usually aluminum. Next - all the gears, arrows, mechanical decimal counters ... Because of its simplicity, which you could not help but appreciate from the description, this type of counters provides inexhaustible possibilities for all sorts of "bullying" over yourself to any intruder who mastered the school course of physics, at least for "four".
The second class . Electronic counters. If the electromechanical counters are "reptiles", then this is already a kind of "mammal", although not yet upright, and a few cloven-hoofed animals, sorry for zoology. They are much smarter, smaller, quicker, occupy all the technological niches that they can reach, and "evolve" at a fantastic speed.
The first commercial models (still hybrid, that is, borrowed a number of nodes from electromechanical forefathers) appeared about twenty years ago, and since then at least five generations of their electronic "stuffing" have been replaced. Now such meters do not have moving parts, they are able to account for electricity by any number of phases and tariffs, "communicate with higher authorities" (work in the automated systems of commercial electricity metering - ASKUE), practically do not require verification, they rarely fail on their own initiative , which is more stable to the ill-fated "rule of the borer," and more precisely at least an order of magnitude. In short, there are a lot of advantages ... But there are two drawbacks that restrain their "triumphal procession": firstly, the price (yes, of course, it falls fast, but electromechanics is still cheaper for today) and, secondly, non-repairability: the qualification of the personnel necessary for their repair should be such that often repairs can be carried out only at the manufacturer, and in general, it is often cheaper to replace the counter entirely.
How are they arranged and why are they more accurate and reliable than their electromechanical counterparts? As you know, power is the product of the current and voltage. Excellent! We measure the current, measure the voltage, multiply, add to the previously calculated ... And so hundreds or even thousands of times per second. From the point of view of the current microprocessors, the task is, as they say, "do not beat the recumbent", and the time left from its solution even to the most "stupid" of their representatives with a guarantee is enough for "communication with higher" systems, and for displaying information on the indicator, and for other necessary occupations. "Deceive" them is much more difficult than the predecessors, but, again, as the classics said, "there are no such fortresses ...".