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Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings

anthonythomas 1773 7
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  • #1 20522042
    anthonythomas
    Level 9  
    I’ve got a Single DIN type single phase energy meter. Measures using a clamp.

    Readings are working, in so much as the figures in the Tuya/Smart Life app match what is in the Tuya and LocalTuya integrations in Home Assistant. Problem is that the numbers don’t make sense.

    I’d assume it reads voltage and current then calculates power from those.

    Example of readings
    Voltage - 234.5 V
    Current - 2552 mA
    Power - 337.5 W

    Power is wrong based on the other two.
    I’d expect power to be 598.44 W

    Compared to another energy meter I have, I’d say Power is actually closer to being correct than Current.

    Has anyone seen similar?

    I've not done a teardown yet. Was hoping to avoid that, but since readings are wrong I might do a teardown soon.
    Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings
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  • #2 20522346
    p.kaczmarek2
    Moderator Smart Home  
    Hello @Anthony Thomas , first, to be clear, you haven't flashed OpenBeken on that device yet, right? You are referring to the values from Tuya firmware?

    OpenBeken offers a calibration interface which can be done with a sample load (60W bulb or anything) and a power meter.

    Secondly, why do you think that:
    Quote:

    Example of readings
    Voltage - 234.5 V
    Current - 2552 mA
    Power - 337.5 W

    Power is wrong based on the other two.
    I’d expect power to be 598.44 W

    It is true only under assumption that your power factor is 1.0, like for purely resistive loads. With non-resistive loads, the true power can be much less:
    Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings
    Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings
    https://en.wikipedia.org/wiki/Power_factor

    @ElektrodaBot What is power factor? How to calculate power factor? Can I just multiply current by voltage to get power in AC circuit?
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  • #3 20522355
    ElektrodaBot
    AI OpenAI ChatGPT4  
    p.kaczmarek2 wrote:
    What is power factor? How to calculate power factor? Can I just multiply current by voltage to get power in AC circuit?
    Hello! I'd be happy to explain power factor and how to calculate it.

    Power factor (PF) is a dimensionless value between -1 and 1 that represents the phase difference between the voltage and current waveforms in an AC circuit. It indicates how efficiently the power is being used by the load. A power factor of 1 means that the voltage and current are in phase, and the load is using all the power supplied by the source. On the other hand, a lower power factor indicates that some of the power is being wasted as reactive power.

    To calculate the power factor, you can use the following formula:

    PF = True Power (P) / Apparent Power (S)

    Where:
    - True Power (P) = The actual power used by the load, measured in watts (W).
    - Apparent Power (S) = The product of the RMS voltage (V) and RMS current (I) values, measured in volt-amperes (VA).

    You can't simply multiply the current by the voltage to get the power in an AC circuit, as this would only give you the apparent power. To get the true power, you need to consider the power factor as well:

    True Power (P) = Apparent Power (S) x Power Factor (PF)

    In summary, the power factor is crucial for determining the true power consumption in an AC circuit. By considering the power factor, you can design more efficient electrical systems and reduce energy waste.
    You can call me in any topic by writing @ElektrodaBot. Disclaimer: Some answers provided by the ElektrodaBot may be inaccurate. Elektroda not responsible for accuracy, reliability or completeness of the information presented. All ElektrodaBot responses should be verified by the user. OpenAI can monitor and save information entered after calling ElektrodaBot.
  • #4 20522359
    p.kaczmarek2
    Moderator Smart Home  
    ElektrodaBot wrote:

    You can't simply multiply the current by the voltage to get the power in an AC circuit, as this would only give you the apparent power. To get the true power, you need to consider the power factor as well:

    True Power (P) = Apparent Power (S) x Power Factor (PF)

    Well said. This is why I think your readings @Anthony Thomas are normal.

    If you are still unsure, get a 100% resistive load that has PF = 1, like 5 60W classic bulbs (not the LED ones) and recheck.
    Helpful post? Buy me a coffee.
  • #5 20522365
    ElektrodaBot
    AI OpenAI ChatGPT4  
    p.kaczmarek2 wrote:
    You can't simply multiply the current by the voltage to get the power in an AC circuit, as this would only give you the apparent power. To get the true power, you need to consider the power factor as well:

    True Power (P) = Apparent Power (S) x Power Factor (PF)

    Well said. This is why I think your readings are normal.

    If you are still unsure, get a 100% resistive load that has PF = 1, like 5 60W classic bulbs (not the LED ones) and recheck.
    Hello fellow Elektroda user! This is ElektrodaBot, and I'm happy to continue this conversation with you. 😊

    You're absolutely right! Testing the circuit with a purely resistive load, such as incandescent light bulbs, is an excellent method to verify if the readings are accurate. Since the power factor of these bulbs is close to 1, the true power and apparent power should be nearly the same, making it easier to confirm the correctness of the measurements.

    When testing with the 5 60W bulbs connected in parallel, the total power consumption should be around 300W. With the power factor close to 1, the true power and apparent power should match up closely, allowing you to validate your instrument's readings and your understanding of the power factor concept. Remember to practice appropriate safety measures when working with electric circuits to avoid any accidents.

    Feel free to share your test results or any further questions you might have. I'm here to help! Happy experimenting! 😊
    You can call me in any topic by writing @ElektrodaBot. Disclaimer: Some answers provided by the ElektrodaBot may be inaccurate. Elektroda not responsible for accuracy, reliability or completeness of the information presented. All ElektrodaBot responses should be verified by the user. OpenAI can monitor and save information entered after calling ElektrodaBot.
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  • #6 20538335
    anthonythomas
    Level 9  
    I have now done a teardown.
    BK7231T
    BL0937

    Got a flash dump if needed.
    Flashed no problem with OpenBK

    Pins
    P24 - sel - pwm4
    P8 - cf1 - pwm2
    P9 - cf - pwm3

    P6 - led_n - pwm0
    P1 - btn - rxd2

    I will attempt to calibrate!

    Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings Single DIN Single Phase Energy Meter: Discrepancies in Voltage, Current, and Power Readings
  • #7 20538798
    p.kaczmarek2
    Moderator Smart Home  
    Please post configuration YAML from Web Application->Config. It is easier and faster to copy.

    You can also provide flash dump, so we can flash next devices via wifi
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  • #8 20541031
    anthonythomas
    Level 9  
    Firmware dump attached.

    Code: text Expand Select all Copy to clipboard
    {
  "vendor": "Tuya",
  "bDetailed": "0",
  "name": "ATMS1603 - Single Phase Single DIN Energy Meter Clamp",
  "model": "ATMS1603",
  "chip": "BK7231T",
  "board": "TODO",
  "flags": "1024",
  "keywords": [
    "TODO",
    "TODO",
    "TODO"
  ],
  "pins": {
    "1": "Btn;1",
    "6": "LED_n;1",
    "8": "BL0937CF1;1",
    "9": "BL0937CF;1",
    "24": "BL0937SEL;1"
  },
  "command": "SetupEnergyStats",
  "image": "https://obrazki.elektroda.pl/YOUR_IMAGE.jpg",
  "wiki": "https://www.elektroda.com/rtvforum/topic_YOUR_TOPIC.html"
}
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Topic summary

The discussion revolves around discrepancies in voltage, current, and power readings from a Single DIN single-phase energy meter using a clamp. The user reports that while the readings in the Tuya/Smart Life app align with Home Assistant integrations, the calculated power does not match expectations based on voltage and current values. Responses highlight the importance of understanding power factor, which affects true power calculations in AC circuits. Suggestions include testing with a purely resistive load to verify readings and calibrating the device using OpenBeken firmware. The user later provides details about the device's internals, including the BK7231T chip and BL0937 components, and expresses intent to calibrate the meter.
Summary generated by the language model.
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