§ 19 The principle of electronic meters.

Microprocessor power meters.

Hello, dear reader. On this page we briefly that much does not bother you, consider a microprocessor-based metering of electricity meters. The main difference between these counters from ordinary induction that they are a little "on-board computer." In these counters is almost no moving parts that perform the measurement of electric current consumed. The counter usually consists of measuring current and voltage sensors (transformers with improved performance), measuring circuits (ADC - analog to digital converters), the microcontroller processing digital signals, data storage counter. The information counter is displayed on the LCD display. They feed on the counters are usually connected to them voltage circuits. In addition, good practice is to install backup power to the meter (in the form of different batteries). They are designed to maintain the integrity of critical information, when the counter is disconnected from the circuit. The values ​​of current consumption is determined by the current transformers. In the future, is the multiplication of current and voltage signals through the ADC high-performance microprocessor with a RISC-instruction set. All information is stored in memory and parallel to the counter displayed on the LCD. The simplest scheme of the counter is shown in Figure 1.

In addition, in various models of the counter can be administered more information outputs (current loop, chisloimpulsnoe relay, in which the pulse frequency is proportional to the electricity consumed, the output of the RS-485, etc.). Almost all counters have the memory for storing program counter of the measured variables (ie, active and reactive energy) as well as a list of various important events (number of inputs to the meter, power supply failure, transition to daylight saving time, etc. .)

A distinctive feature of these counters - is the possibility of accounting for electricity tariffs. This means that you can pay for the electricity consumed in different ways. For example, there are three tariff calculation for electricity - peak (usually morning and evening), semipeak (it's practically the whole day except morning and evening) and a night. Price for electricity varies depending on tariff. For single price is 0.1271 1kVtch hryvnia, but if you decide to pay for fares that you will need to multiply the price n the following factors:

Obviously, it is most advantageous to operate at night tariff (price per 1kVtch less than 4 times). In the old induction meters you could not take into account the transitions to different time rates (for this it was necessary to put the person at the counter, which is followed when it's such a peak rate and recorded the readings.) As a way could be to use a computer system to gather information in real time and then manually partition into intervals according to the tariffs. However, much easier to put a microprocessor counter, an internal program that she would be watching the transition from one zone to another tariff and the consumption recorded separately for each interval.

In addition, these counters can be a good diagnostic tool. For example the counter "Alpha +" ABB VEI Metronica (Moscow, Russia) can act as VAF (volt-ampere-phase meter), show rms current and voltage, harmonics, etc. (See Figure 2).

Counter ABB VEI Metronica

Example graphs of electricity consumption.

Figure 2. Screen of the program counter "Alpha +".

In addition, given the high accuracy class of schtechika (0.2 - 0.5) and the lack of self-propelled (ie samoprozvolnogo drive traffic, as in the induction meter) can be said that to date these counts the most convenient option for electricity metering .

To counter can count and display the data it is necessary to make a program that will "indicate a" counter what to do: how to measure, what to measure, where and in what form the record. You must have a personal computer with special software that comes with counters, the counter itself, a special probrazovatel to transfer data from computer to the meter. And, by and large, all counters are programmed by the same rules: the user does not have to write programs in some programming language - all that was required of him - this is just to answer the questions of the program and mark the appropriate arm of the options schechika. Sample window for the counter "Quantum D300" firm Schlemburzhe (riunok 3).

Another of the useful properties of the counter data - the ability to create on their basis of the information system for collecting and processing data on electricity consumption. That is, You can on the basis of these counters to create an automated system for collecting information. Suppose you have a few sites (substations or small factory for the production of products) and you want to control the flow of electricity on the objects. Nothing could be easier - you bet microprocessor counters on the point of recording, connect the modem to them (pulse relay output RS485) and collect all the information on one PC, which stands in your office. Even if you need to reprogram the computer - you can do it remotely via modem. And then immediately the question arises: What if I have "bad man" and want to get into and change the data in the counter? At this point in the counter has a "response to Chamberlain." Normally counters are several levels of access to their information (for reading, modifying, reprogramming). In addition, the memory counter contains information about all the reading and trying to call it. So you can determine when the data is changed in the counter.

Here, dear reader, I will finish my story, so you can rest a bit. The next time we'll talk with you and various automated systems that can be constructed on the basis of microprocessor-based counters. Sergei Kibtkin.