§5 How the electric meter is arranged
Usually for tenants the counter is represented in the form of a "black box" through which the wiring goes to the apartment. This "box" somehow, he knows in a known way the amount of electricity passed through it, for which we sometimes still get paid. I think that if you are a metrologist (a person who professionally deals with various measuring instruments), then you do not need to waste time reading this article, you already know everything, but if you are an ordinary person, read it, you can learn something new .
How, or what, makes that aluminum disk spinning in the counter. Maybe there is a small motor that drives your spent kilowatts? Can he spin just like that, on his own? Well, dear reader, I inform you bitterly that we will have to sink briefly into the jungle of physics and electricity.
Let's take a look at the drawing. The movable part of the counter consists of an aluminum disk 1 placed on the axis 2. To calm the oscillations of the moving part, a permanent magnet 4 serves. The rotational moment of the disk is formed by the electromagnets 3 and 4. The electromagnet 3 has a current winding connected in series with the measured load, and along it there passes a current creating a magnetic flux (for simplicity, imagine that this is some field that appears when the current passes through the conductor). The magnetic flux passes through the disk twice, closing through the parts of the magnetic circuit 4 and forming two streams in the gap. There is such a rule, called the rule of the "left hand." If you place the palm so that the lines of force of the magnetic field enter into it, and the elongated fingers indicate the direction of the current, the retarded thumb will indicate the direction of the force acting on the conductor.
The horror, while reading this rule, almost got tired. If you do not understand anything, then in general this means the following: there is a current flowing through the coil of the counter, a magnetic flux appears and as a result we have the force that will turn the counter disk in a certain direction. This rule is used by some bad people trying to deceive the meter, changing the direction of the current flow. The rule of "left hand" is triggered and here, the direction of the force acting on the disc changes.
recently began to appear meters of electric energy of a new generation - microprocessor. Their main difference is not so much the principle of obtaining data (current and voltage transformers remain transformers), but the mechanism of processing, access to the data obtained. In these counters there is no disk that rotates, in them analog-to-digital converters (A / D) and microprocessor (MP) make a sample of current and voltage to obtain the final result displayed on the meter display.
Microprocessor electricity meters (Schlemburge companies on the left and ABB on the right).
- Accounting for multi-tariff regime (i.e., the counter counts for different prices during peak hours, night and semi-peak hours);
- Many options for accessing the counter (via modem, current loop, RS485 \ 232, etc.);
- A large number of additional parameters displayed by counters (within a hundred) - peaks, load schedules, calculations by tariffs, average values, etc .;
- The accuracy class of such counters is higher (i.e. better) by an order of magnitude compared to inductive 0.2, 0.5 versus 2.0 induction ones. True, for this in the accuracy class there must be transformers, to which such counters are connected.