Recently I was told why for accurate power measurements of appliances operating from the network, you need a special device — a power meter (wattmeter), and any measurement using conventional multimeters may not be accurate.
My first power meter BEBUY I bought five years ago in one of the Chinese online stores. He, like many other similar measures, is quite accurate in the measurement of capacity from tens of watts, but low power measurement accuracy is reduced.
In one of the reviews led bulbs on the website led-obzor.ru I saw a picture of the power meter that showed power values to hundredths. I asked the author of the website that it's for the meter. It Turned Out, Robiton. At this manufacturer there are two models of power meters: Robiton PM-1 and PM Robiton-2. I asked the representatives of the brand to provide me with both a model for close study.
Devices is not much different in price (PM-1 is 780 rubles, PM-2 white — 900 roubles, black — 1000 rubles), but very different in capabilities and accuracy.Possibilities of
Both instruments are included in the earthing-pin, and the load, the capacity of which is to be measured, are connected to the socket on the unit. Both devices have three buttons. Both devices are capable of measuring power up to 3600w.
The instrument measures power, the amount of energy consumed by the load (kilowatt-hours) and cost of consumed energy. The price of a kilowatt is configured.
Measurement resolution power is not very high, therefore, when the load 6 watt readings all the time "jumping" between 5.5 and 6.4 watts.
The power meter Robiton PM-1 is ideal for measuring power and energy consumption value of the electrical medium and high power machines, heaters, kettles, refrigerators, washing machines.
Robiton PM-2 has much more features and higher accuracy.
Three batteries are used for the built-in clock and save the readings after disconnecting from the network.
Device displays time, voltage, frequency, current, load power, power factor (Power Factor), time of measurement, the amount of energy consumed by the load (kilowatt-hours) and cost of consumed energy. The price of a kilowatt-hour is adjusted to account for day and night consumption with two-tariff accounting. There is a possibility to reset the measurement time, power consumption and cost.
The accuracy of measurements
in order to understand how accurate the wattmeter, I have used the whole Arsenal of instrumentation.
As a source of reference voltage 230 V, I used an uninterruptable power supply with pure sine wave APC Smart UPS 700INET mode battery life.
The most accurate of my multimeters — Mastech MY65 (accuracy ±(0.1%+3), i.e., ±0.53 At 230 V) showed 231.2-232.0 V. Presumably, the source gives 231.5 V. Robiton PM2 honestly showed 232 V. Multimeter UT61E unit inflated statement, but its accuracy (±0.8%+10) is only ±2.84 In 230 V.
As low-power measuring load I used a resistor 27 ohms 2 watts. MY65 (accuracy ±(0.3%+1)) showed that its resistance is 26950 Ohms. Power should be 231.5/26950*231.5=1,9886 watts. Robiton PM-2 showed 1.99 watts. Perfect exactly!
Robiton PM-1 show alternately 1.8 and 2.0 watts.
In addition, I measured the power of incandescent lamps of 25 and 75 watts. PM-1 showed 25.7, and 75.4 W, PM-2 — 25,95 and 75.58 W.
I have had the opportunity to compare the results of power measurement wattmeter Robiton PM-2 with the results obtained on expensive laboratory equipment to measure the power, and even at load with low power factor and "ragged" consumption — led bulbs. Ten different samples of lamps with capacity from 3.4 to 13.8 W of the deviations ranged from 0.2% to 2.1%. Great result!
Despite the wide range of measurements, Robiton PM-2 gives very accurate results even at low power.But what's inside?
In order to open the power meter, you will need a cunning triangular screwdriver. The design of the PM-1 consists of two circuit boards.
On-Board indicator has the calibration button. I decided not to risk and not to press it.
The measuring shunt.
The reverse side of the main Board.
Design Robiton PM-2.
The main Board and the shunt.
Charge on the reverse side.
Power meter — an inexpensive and useful device that allows you to know how much different appliances consume. With the help of it you can know how much a refrigerator consumes per day that is consumed by a washing machine per wash cycle or to find out how much it costs one boiling kettle. With this tool you can determine which appliances in the house consume the most energy (believe me, this is not the most powerful devices) and learn how to save energy.
Of the two wattmeters Robiton I certainly recommend Robiton PM-2 — it is more accurate and has much greater opportunities.
P. S. And remember, only by changing their consumption — together we change the world! ©
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