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With the rapid development of electronic computers, electronic (digital) replaced electronic meters. The principle of operation of any electric meter is based on combining the instantaneous values of current and voltage consumed from the network for a certain unit of time for subsequent display on a counting device in the form of ready kilowatt-hours.The electronic counter consists of the main components:
- current and voltage sensors;
- a power converter to the pulse frequency (KR1095PP1);
- central microcontroller (control device-MS68N05KJ1);
- permanent-memory device (ROM);
- controller of the liquid crystal display (LCD-К182СВГ2);
Electrical signals from the current and voltage sensors are fed to the power-frequency converter, which performs the multiplication operation, receiving the power consumed. The received value of the power converter is transmitted as a pulse to the input of the central microcontroller, which, in turn, sums the pulses in a certain time, getting kWh. The central microprocessor transmits data to the LCD microprocessor, which, in the end, will be displayed on the display.
To save the meter readings in case of power loss, the EEPROM memory is used. If the meter suddenly becomes de-energized, after it is turned on, the microcontroller first extracts the last stored value from the ROM and displays it on the display. Then it continues to count the pulses from the converter, exchanging data with the EEPROM, and increases the meter reading.
By making changes to the program of the LCD microcontroller, you can set different modes of displaying information on the display such as date, time, load consumed by tariffs, and more.
The presence of an external interface channel for the electronic counter, using the RS-485 example, allows the counters to be grouped together and transferred to the power supply company, which allows the consumers to turn off the electricity in case of non-payment.
As a current sensor serves measuring transformer (current transformer) or shunting plate; voltage sensor - voltage.
Three-phase electronic counter has the same design and has the functions of displaying on the display active, reactive and full consumed electricity, etc.
Energy meter of Energomera, appearance
In this article I will tell and show in the photo how arranged electric meter. For an example, let's examine (open) the counter Energy meter CE 6807 P production of the Stavropol Concern "Energomera". Look at the counter on the left.
Counter Energomera CE6807P - one of the simplest in design, the easier it will be to consider its device.
By the way, on electric meters on the blog SamElektri.ru published several articles:
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How the energy meter measures energy
As always, first - a little theory, so to speak, opening remarks.
First of all, the meter differs from all other home electrical devices in that it is switched on sequentially with all devices. That is, the electric meter circuit is arranged so that through it passes all the current that it takes into account. Well, if the current does not pass all, then it is very disliked by the regulatory bodies of energy surveillance.
As it happens - in the Theft of Electricity, or the discussion of it.
The current passes through the counter through a special calibrated shunt with a certain resistance (hundredths of Ohm). According to Ohm's law, a conductor, through which current flows, creates a voltage directly proportional to the current and resistance:
U = I · R
This voltage uniquely determines the current. Voltage is measured, and so the current also becomes known, indirectly.
The power consumed by the appliances in the apartment is equal to the current multiplied by the voltage:
P = I · U
But how do you know how much power "eaten" electrical appliances? For this, the power is multiplied by the time, the electric energy is obtained:
E = I · U · t
Per unit of measurement electric power, which shows how many kilowatts passed through the meter within an hour took kilowatt per hour, abbreviated - kWh
Strictly speaking, the energy is more accurately measured in Joules, as we were taught in school, but the unit of measurement kWh. Write exactly to the point, as for example the total electrical power is measured in В · А.
Often incorrectly written - kilowatt / hour, kilowatt-hour, or even simply kw. Such confusion might not have happened if one unit had been invented for a unit of electrical energy. For example, Electrojoule. Or they would be called by the name of some other scientist.
And the registration and indication of these "Electrojoules" is implemented by simple electrical transformations and devices. Let us consider them below.
How the meter is arranged
Single-phase electric meter device direct inclusion The energy meter will now be clearly visible in the photographs. I recall his appearance - on the first photo of the article.
I got a good counter, they gave it to me, because the owner of the room was replaced where he stood, and the new owner was obliged to change the counter.
The meter usually has 2 seals, one protects against unauthorized access of the counter terminal, the second - electronic circuitry counter. There are no more seals on my meter.
Let us consider the terminals in more detail.
The terminals are clamping, keep the stripped wire well throughout its entire length.
Now the most interesting is to open the meter body:
The counter of Energomera ts6807p. Removed front panel
Energy meter. Cap removed, photo 2
We take the gut of the interior, and see that the circuit of the electric meter consists of three main parts:
This is 1) a stepping motor, on the axis of which the digits are fixed, 2) a board with a controller and 3) input terminals. Apparently, all Chinese (I hope, except for the terminals), so the price of such a counter is 650-750 rubles.
By the way, did not see, but in Mercury the production of components is Russian. Who will confirm?
Terminals and board with controller. All is inverted, so the phase terminals of the counter are on the right, the zero terminals are on the left, not as we are used to seeing.
White and green wires are the output of the measuring shunt. The same shunt, which "settles" the voltage proportional to the current through the phase terminals. This voltage is applied to the inputs of the KT1 and KT2 boards and fed to the controller for processing.
Also from the phase terminal, power is taken to the controller, this is a yellow wire. Power - transformerless, through a capacitor, rectifier and stabilizer 5VDC.
A null terminal is used to take the second pole to power the meter. And also in order to provide a connection, and to limit malicious circuits to turn on the counter.
From the output of the controller card, points M1.1 and M1.2 receive pulses to the stepper motor. The one that is braked with a magnet. The pulse frequency is proportional to the current, and is additionally indicated by the LED.
About the stepper motor is told in my blog in the article about.
This LED is used to check and verify the meter. Count the number of pulses after (for example) 5 minutes, and look at the correctness of the readings on the front panel.
In the controller, a program is programmed, which generates pulses for the operation of the stepper motor.
By the way, the program can be changed, craftsmen do it. This can reduce the meter reading by 30 to 50%.
Here is a photo of the PCB of the counter is slightly larger:
What are the details of the counter circuit
As you can see in the photo, the scheme of the electric meter of Energomera is very simple, the basis of the scheme is a microcontroller that manages everything.
In the photo, the details are not clearly visible, so I rewrote some of the denominations.
Stepper motor (recorder):
Step counter logger. Buy this can be through the Chinese site meter-counters.com. This registrar is magnetized and the counter is stopped.
- Stabilizer for 5 volts 7805,
- PIC controller MPC 3905A,
- Opto-coupling for telemetry (remote reading) PC817C,
- Quartz at 3.579545 MHz.
Instruction for the Energomere meter
Below is the instruction on the counter Energomera CE6807, which is considered in the article. There are all the parameters, the wiring diagram, as well as the device and the principle of the counter according to the manufacturer's version.
There was still such a piece of paper to correctly write the testimony:
According to the rules, the figure denoting the fractions of a kilowatt hour, must necessarily be highlighted graphically. Which is the case, see the counter photo in the case.
