#347 

Mr. Spiess: Beautiful but... your Power Factor formula at 17:57 is wrong. It is not P/Q but, instead, P/S. Power Factor is the cos(theta) and the closer to 1, the better.

The "One hand rule" was the first thing we learned at school. Seeing it in this video, also as first point, show how well educated and well versed Mr Spiess is in Electricity and Electronics.

An excellent review of the topic. I had forgotten allot of this. Power factors, RMS and needed a refresher. Very educational and you are a great teacher. Thank you.

best content to see before bed time in NA, thank you Andreas! Very informative, simple and Swiss accenty. Happy to be in the front row.

Thank you very much for making such videos, which helps not someone who learning electricty from 0, but jump-starters and diy-ers who started w/o advanced/deep-basic knowledge in electricity!

I'm gonna need to watch this video again and again to apprehend the concepts, but its clearly explained as always. Thanks Andreas!

Excellent, as always. Thank you for an instructive and entertaining video. Much appreciated.

As an electrician mainly working in commercial settings (3 phase here) I am extremely jealous of your 3 phase residential power! Sometimes the single phase (one 220v phase split to 2 110v legs) we have for residential power is very annoying! Very interesting video, btw. Thanks for all you do for us out here in RU-vid land!

Excellent job covering the top. I very much appreciate it!

I loved the video and how it is presented. Very practical and of great didactic contribution, a pity not to have seen it until this 2022! I just found your channel, you already have one more subscriber.😉

Good Job ! it's a real pleasure to watch you ! Please continue , .. Success !

Grest work, as always👍

Thank you for putting the links in the description.

Thanks sir, very informative and useful for my projects, and the information delivery is very good. Subbed!

Great video as always 👍 Thanks for sharing 👍😀

from what i remember from my tuitions, power factor can be corrected by using capacitors of the right size on the mains wires. However there's another neat trick : if the mains are 3-phased, and the power factor is similar between all 3 live wires, the power factor can be corrected using a synchronous AC motor (yes, synchronous, not asynchronous) that runs without load. It'll probably heat up, but the motor ends up consuming the bad power factor just as capacitors would.

When looking at RMS to DC converters, it good to look at how well they respond to the signal "Crest Factor" which is an indicator of how close the signal being measured is to a sine wave. e.g. Crest factor is a parameter of a waveform showing the ratio of peak values to the effective value.

If only I'd seen your video 18 months ago. Caught out by measuring voltage and current across different phases. Data looked correct but power consumption was too low compared to the bill. Turns out the electrician that did the install of 3P meter had an off by 1 error with the voltage feed on the 3P bus bar. Took me a while to figure that one out. This was using Schneider Electric measuring gear. Quite accurate but expensive. Great work as always.

Thank-you Herr Eng. Spiess for all of your great videos. Your information is always accurate and very professionally presented. In North America, houses do indeed have a 120/240 V split phase system that work well. Large apartment buildings often have three phase systems with 120/208 V, using the phase voltage to create 208V rather than 240V. This is annoying as kitchen ranges and clothes dryers meant to work on 240V are now operating at 208, which delivers only 75% of the expected power.

never heard that advice about the hand on the pocket. great way to not forget !

great teacher as always

This video was extremely useful!! I am in the process of making a datalogger with Arduino and also exploring different methods to connect to mains and DC powered devices. Thanks.

thanks for this video and also for your wonderful youtube channel ❤️🌹

This is a really great video, thank you

It's a pleasure to sit in the first row :)

Thanks for the explanation of the meter at the very end. I have one of these and wondered about the watts reading when the power factor was low. I have a solar system and inverter so the power coming out of my inverter is not accurate just from the watts reading unless power factor is 1. When you explained that it should be labeled VA that makes more sense to me.

Excellent explanations.

Very well explained!!!

the chips graphic was Hilarious! well done

Great videos! 🥨🥚🍟

Very useful, thank you!

Superb video!

Excellent video.

In addition to better measurement, another advantage of the Sonoff Pow R2 over the older version is improved fire safety of the design.

I built one of these home energy monitors for my split phase system using two CT clamps, an AC/AC transformer, an Arduino Uno, and Robert Wall's EmonlibCM. The latter is essential for this project because he takes all the complex calculations from an electrical engineering PHd background and does them for you, to the precise timing known on the Uno's chipset. It's also surprisingly dangerous - even though the CT clamps aren't actually touching the mains wire, if they do not have a load resistor or a TVS diode, they will explode in a big puff of smoke if you clamp them around a wire carrying 100 amps+ of current. Because with no load resistor, they will generate theoretically millions of volts. As i nearly discovered.

Hi Andreas. Excellent and accurate explanation. In Italy only those who request a three-phase contract receive all three phases: the energy meters are simpler and less expensive (from corridor whispers they should cost less than 40 euros each to the energy distributor, considering that in Italy only for E-distribution we talk about 33 million meters, three-phase and single-phase together ... with a hundredth of difference each we make a good figure. I have seen that in Germany, the only country where I have been able to see a home meter, instead they carry three-phase electricity also in homes, I don't know in the rest of Europe. Here in Italy, at least years ago, before the liberalization of the market, (Enel was a non-profit national body, but in fact it was a monopoly) the customer who wanted a three-phase contract in a civil home had to sign an indemnity on the dangerousness of the voltage at 400V. In all cases, the distribution lines are all three-phase at 400V, with the same cross-section of cables it transports twice the power compared to a single-phase system, but the derivations for the individual supplies (we could improperly call it the last mile) are all single-phase to exception of those who specifically request a three-phase supply

The Kill a Watt type meters are convenient and have become reasonably inexpensive.Two uses I find they're handy for are for checking the output of my old school generator, and for establishing an idea of how much power small appliances use.

In the US we do have 3 phases but that is typically industrial although a residence can have it if it is available at the local distribution point, is needed and requested. Residential customer might have to pay for that in fracture to be installed up to a point and the voltage on each phase is 208 with respect to earth/neutral/common. The two phases you talk about is simply single phase coming down the local transmission lines [2 wires/14KV] to a transformer that puts out 240V with a center tap that is used as neutral to reference 120V off of each line. This way it is single phase 240V and when referenced to neutral 120V using only half of the phase but still 60Hz.

Great content.

What a nice topic!

Nice video, and a complicated topic. One thing not covered here though, don't always expect the Current waveform to be sinusoidal. Switch mode power supplies, CFL bulbs, LED lamps are all non-sinusoidal and measuring power factor, and true power is very difficult. These modules make this possible because they have delta-sigma converters and an 'algorhythm' to determine the true power. You can use the LTC1966 AC to true RMS converter to do the RMS calculation for Voltage and Current. Then regardless of the wave shape the power factor can be calculated (V_avg * I_avg) / (V_rms * I_rms). Have a look at those modules, they work really well with Arduino.

Thanks for the info..👍

Ur vids are good

Excellent !

I have a SonOff V2 and it measured for over a year on the same walll plug the more reliable energymaster was used for. After 1 year and 500 kWh consumption the difference is below 0,4% or less than 2 kWh. Did not change anything. Since then I purchased a different model that is housed in a plug in plug design switch for 16 A max. Results are 0,5% different so not that bad to get behind consumption of a dryer over a year to see that seasonal curve if that exists or that of a washing machine or even a night light outside and its movement sensor. It is a 32 Watt fluter and used 1 kWh per month so just 12 kWh a year. Who knows what a light does during the deep night so we measured to be sure that this is not a silent or hidden energy burner. If you check each single pluged in device and also the directly grid connected pieces like window jalousies you get a good feeling about your home energy consumption and efficiency especially if you make an inventory list of all devices and its standby watt and usage and an estimated use time per day ... If you then enjoy your holiday you get behind if your standby estimation and device inventory is right or not. That makes things easier to change habits or devices ... for example a smaller oven to heat up for just a fresh bread or piece of pizza instead of the usual oven which takes kWh to heat it up before starting to cook. When do you turn of a water cooker ... if it is already cooking or earlier and what is the difference? So we measured the water cattle for a quarter and guess what: it is used far often or with more water than assumed. It uses 5% of household energy consumption ... for tea mostly.

Thank you very much for the very informative video. What is the Type of the Battery powered oscilloscope, and where can it be bought?

P = V*A ill have to digest that on a monday morning :) Awesome video.

*boom* - that was the sound of my brain after getting to the end of your video

Three phase power is used in the United States in places like almost all of New York City. The Two phase system allows for larger appliances to run on 240v compared to most other household appliances which run on 120v. This way most normal homes have 120v wiring with occasional outlets at 240v for high powered AC units, clothes dryers, and ovens. With a standard wall socket voltage of 120v, the three phase wiring would only provide 208v and not 240v. This is actually convenient in places like NY City where they don't want the consumer to be running high powered devices like electric ovens or electric clothes dryers which are, as far as the electrical grid is concerned, better powered by gas.

How could I measure real time power on a 3 phase system. I saw I could use a 6 channel ESP energy meter. Because I wanna do it with ESPHome and homeassistant. But I dont find that board here in germany (Shipping is very expensive ) What would you recommend me ? Thank you !

The yellow Metrrixx multimeter has the state of an old Nokia cellphone. Always reliable, tough and still working after dropping from the ladder. Only changing the mA fuse from time to time and a battery every year (if you did not forget to switch it off) 😉

Hello Andreas, thank you for another brilliant video and all the work you do on this channel - to start with. Concerning the measuring device shown at 23:22 - I absolutely do not understand the wiring diagram on the website. Could you please explain where to connect L, N and the leads to the load to these four connectors on the device? Must be a mental hickup... Thank you!

In the UK we normally ONLY are supplied with a SINGLE phase supply. The three phases of a local final transformer are shared as equally as possible between multiple houses. e.g. the first pair or first two pairs of houses will be fed from one phase, then the next group of houses, then the third group from the other two phases Some households MAY receive a three phase supply if it has been requested (and approved) from the distribution company. This may or may not be the same company who bills the premises (more commonly not). If a business is being run from home premises that requires three phase, quite often, depending on the area, the local council will be told and business rates applied to the premises! That is AFTER they may take you to court for unlawfully setting up a business without gaining planning approval first!! Smart meters in future will almost certainly start charging (and more costly charges!) for reactive power since it causes current loading problems for the localised grid area - the reactive (but REAL) current can exceed the local capacity of the grid cables, hence requiring more expensive infrastructure. This is "partly" due to the massive increase in non PFC compensated switch mode power supplies in homes driving SELV (low voltage) LEDS. It is also complicated by the increase in solar PV usage WITHOUT the relevant storage of the excess which instead goes straight back to the local grid.

There are 2 reasons to measure AC mains. 1) Because there is a need to know how much power is being used. 2) To know *IF* power is being used. This video had great information for case 1. But, what about case 2 ? True, if the answer is available for case 1, then case 2 is known. But, case 1 is often more complicated and more expensive. What about a simple cheap solution to case 2. But, you may ask, why be interested in only case 2? For example, a microcontroller can be used to mimic the IR input to a lot of IR controlled devices, like Air Conditioners, TVs, and a lot of others. Unfortunately such a device does not give good feedback to the microcontroller, so the microcontroller can't know if sending the "cycle power" command worked and actually turned the device ON or OFF. One way the microcontroller can know if the device is turned ON or OFF is *if* the device is using power. Exactly how much power is of much less concern, maybe only that the ON state is a lot more than the OFF (or standby) state. Here is a simple solution that i used which is protected from mains: In a video #321, "the guy with the Swiss accent" mentioned some current sensors usually built off of the Allegro ACS712 hall sensor (or something similar), which he rightly discouraged for use with mains - at least as-is. Only with luck will that chip work with mains. And relying on luck when working with mains is a quick way to posthumously earn a Darwin Award. Since that chip is only rated for a working voltage of 100v - sending 120v of mains AC through it might work, but it's not a good idea; And if your mains are 240V... that's almost 700v peak-to-peak and not to even be thought of. However, that little chip (or any similar chip) can be coerced into working with mains very safely - although it comes with a loss of accuracy. Again, if the real question is *IF* power is flowing, then accuracy is not very important. Here is what i did: I took a large eye-hook screw (4cm or 1.5inch diameter) that a magnet would stick to (stainless steel is not good) and sawed of the screw part, this left an iron loop with a small gap where the loop comes together. Then i wrapped some heavy gauge insulated power wire around the metal of this loop. Starting from near the gap i wrapped a spiral around the metal until it got to the other side of that small gap - i got 25 tight turns. Then i used hot glue to place one of those the hall-effect sensor chips into the center area of the gap... you want the gap just big enough to fit the chip without damaging it. Power from one line of the mains goes through the heavy duty wire in the loop. If the wire used is designed for use with mains power then this is as safe as any extension cord since the mains power is completely isolated (as long as the insulation does not melt). And now the microcontroller can read the hall sensor to see if there is current - and if is current flowing then power is being used. The reading is not exactly accurate - as particularly at very low current flow there is a fair amount of noise. But since the difference between stand-by and someone actually using the microwave oven is really huge, my microcontroller can easily tell if the microwave was turned on. On the software side, the program must be aware that this signal is AC and switches from positive to negative flow 50-60 times per second. I have mine probe as fast as possible for 200ms and average the absolute value of the results. But that is a whole other discussion.

Great video, thanks. I would like to ask about the model of battery powerrd oscilloscope and where Can I buy he same?

Nice video

Excellent ! Usefull, indeed. A nice wrap up and prep for evening classes starting in September. Well, that of course depends on the Corona issues, but let's think positive. Great entertainment too and as usual every time I see your oscilloscope up close, I start drooling...

Great videos! This one and 321... Working on a project that will turn on and off a load of less than 5amps at 110v... Want to include power monitoring and I am using acs 712 for now... For this application what would be the advantage of a more complex solution as the ones you presented here?

Great video as usuaI. I also share your concern about connecting to mains. It's great that we now have smart plugs with built in monitoring but I wonder about the accuracy. For constant loads directly connected to the panel, it might be easiest to read the nameplate or use a Current probe with your multimeter. Then monitor when the load is switched on. For variable loads (like my heat pump) I thought about the AD8210 Current sense amplifier and a current transformer and burden resistor. Current transformers are evidently an accepted practice. My solar panel installer put one in my panel.

How interesting to see the PF of that dimmer

Good stuff! Any recommendations on AC current meters which output a DC proportional voltage? This would allow the ucon to do other stuff and just read at any time.

Hi Mr.andreas you show device at 9:10 . I want to detect AC mains (healthy voltage) does it do the job? I am building a device which can see whether mains voltage is ok or not. It is ok if voltage above 200v ac if it is below 200v it is not healthy phase. What do you recommend to use in this scenario?

Do you, by chance, know if the Shelly EM can be "tasmotized"? Once again, thank you for sharing your knowledge

Sir for measure voltage and current on single phase transformers for test automation! Could you please provide me some hints thank you

Hello, thanku very much for the informations, very helpfull, i would like to ask how much is the phase angle error for current transformer?

I always look forward to your videos. so professional and informative! do you have a recommendation to measure mains power before the mains breaker? There are occasions when city power is down and i open the mains breaker to back-feed a generator power to the mains panel. i would like to monitor when city power is restored. My intention is to find a suitable sensor to monitor one or both 240 mains cable in the power panel. I understand the a cable clamp is used to measure current, however, since the mains breaker is open and voltage is present from city power, no (home) load is connected so i assume zero current. can a current clamp be used to sense when the city power is restored? I would like to measure any voltage activity on city power and have an Arduino trigger a relay to provide an audio indication, then silence the alert. what contactless/clamp sensor would you recommend? I release you of ALL liability when answering (thought i would add this for your protection). Keep up the OUTSTANDING work, Sir!

14:45 About CT by clamp to Neutral wire, but if your wire (line) of my house is Live (Hot) 1/Live (Hot) 2 wire from DU (220V 50/60Hz). How can i use this CT?

Could you please assist in testing current of PCB tracks. I have a problem where I have a short on a pcb and need to track it down. I have been told there is a probe that will show the magnetic fields on pcb.

The other thing to note for left-handers: It's very difficult, but try to keep your left hand in your pocket rather than your right. Current will always flow through the easiest path to ground and that means (unless your heart is on the right - a VERY small minority are) then slightly more current will flow THROUGH your heart to ground from your arm down your left side. Current will still flow down your right side too but your heart is not in the way. If you receive a shock through your right arm, current will still flow through your heart, but mainly NOT and in any case will be much smaller, hence marginally safer.I learnt this over 50 years ago from an OLD TV engineer who used to have to work with 10kV to 35kV or more in CRT TVs. The bigger the screen, the higher the voltage (usually) and colour screens more than mono.

5:00 was the scope saturating at the peaks or was there another component/source issue?

Thanks 2 U, guy with swiss accent!

Learnt two new tricks. thanks! How can I measure 20kHz 70% dutyCycle pulsed DC current?

Hi andreas any everybody, 12:37 can you suggest how can i measure current with bare zmct103c. Any article or links please..

I am a retired Electrical Engineer and I found this extremely interesting and there are a few places where I need to watch again because you said something which surprised me. Power Factor correction is extremely important in industry and the supplier will shout at you very loudly (as well as charging you) if it drops low. The domestic user pays for power factor indirectly because VAR does not do any work but you pay for it. During my Apprenticeship Elec Tech called this Wattless Power. I need to look at your Oscillospcope traces again mainly. At 75 yrs old I do not need to, just curious. Thank you.

13:16 - Also as I recall if the voltage across both wires is not 0, you have a leak somewhere if you haven't noticed yet (usually it's sparkly and hot)

@9:20 What should be the distance between AC and DC? Arent optocouplers made to withstand 2kV'ish+ volatages? Or the typical pcb not suitable for such clearance?

Can you also access the data from the power monitor with the display (called P06S apparently)? I didn't find any information about a serial interface like the PZEM-004T has. Would be nice to have a display and broadcast the data.

Any one any idea how to measure L1 AC mains current AND current DIRECTION with a split clamp current transfo and arduino ? Like to know if I'm injecting or using from the net and how much (not taking into account the PF)

Thank you. I get really crazy of al thos people saying volts, amperage or wattage..those people probably also say they ran 200distance..

@Andreas Spiess I want my esp8266 to log power consumption of my air conditioner. Which module to use ? I am clueless. Please Help.

Hi Andreas Is it possible to use PZEM044T for three phase(ac) power measuring hooked with an arduino? Am Working on a diy project for measuring 3phase current & voltage for a 240AC motor. Any other better ideas too is a welcome.

Both AC/DC voltages and Currents can be measured safely (isolated) using chips like ACPL7900 or equivalent. They produce a differential voltage in proportion to input voltage or current.

Would love to see some testing of how accurate (or not) the Sonoff devices actually are.

Hilarious - the arm thing. Good presentation. Especially for lay person...

I, for one, love the Swiss accent. But i must know: are you saying "pretty youtubers", "greeting youtubers", or something else at the beginning? 😂 Great comprehensive AC video. I loved it.

This is something i was looking for. But how can i send that 21:21 data to a server to monitor the readings online

I'd like to know if there is a device that will tell me if I am feeding power to the grid or drawing power from the grid. This is to use excess solar power in water heating and battery charging. Is there a device that will tell me this? (Or do I have to build something to detect phase of current/voltage and then work it out from that assuming I don't have a motor running that will skew those results)

Is there any dc voltage and current measurement video for 16cell 100amp lifep04 cells. Want to make bms with esp32 is it possible.

Andreas, when will the second row seats start to get occupied?

I want to put a power monitor for the apartment in my fuse box and publish via mqtt. The FI seems to be only 25A. What's the best choice for accuracy+speed (want to try to detect different devices by their power profile like sense.com)? I have a PZEM-004T with a 100A CT but haven't put it in yet. How much more accurate would a 30CT coil be? Are the CT versions just safer or also less precise? What about a Sonoff Pow R2? It seems to be only 20A, but I guess that'd be enough. What happens if it went over 20A? Many questions :)

Here's an interesting question... How would you go about monitoring actual high voltages? ...ie electric fence voltages (~10kV, ~150mA, 1Hz ...but with short duration soliton pulse) I made a few Lora fence monitors and am using basic voltage dividers. Looking for a more robust solution measuring voltage using opto isolators though.

Power factor is a big problem for those current transformer devices that are sold to be clamped around the main tails to/from your electric meter in order to report the consumption of the whole house, even when the installation only has one phase delivered to it, as is the case for almost all UK houses¹. The ones I've used don't measure the mains voltage - *at all*, let alone in tandem with the current - and yet they report power rather than current, so presumably they're just assuming a mains voltage of 240V RMS and an arbitrary power factor?! I've used three such devices - the Energenie Mi|Home MIHO006, the Loop electricity monitor, and the Owl CM160 - and they all reported power consumption figures that were *significantly* wrong: in the region of 30% out! They each reported different figures, too, so it seems they're using different assumed values. If the difference was only 5% or even 10% I wouldn't care nearly as much, but 30% is unacceptable, IMO. The mains voltage here (as measured by a couple of TP-Link HS110 devices and imported to InfluxDB+Grafana) has ranged from 230V to 245V over the past month, so even assuming that to be constant introduces some amount of error... These days I'm using an ESP32 and a phototransistor to measure the duration between the flashes of the red LED ("1000 imp/kWh") on my electricity meter, very similar to the system described here: esphome.io/cookbook/power_meter.html (though I'm using ESPHome's "pulse width" sensor, because ESPHome's specific pulse counter implementation means that the more frequently you want it to report a value, the less accurate its readings get, to the point that, with a report every ~10 seconds, I had a *resolution* of around 400W!) This method is very accurate - it matches what's displayed by my utility-provided smart meter's in-home display - and since it uses the meter's own measurement hardware, it doesn't have to worry about the power factor - it would even automatically switch to reporting VA if my supplier decided to start charging me for apparent power, as Big Clive suggests they will! ;) ¹ Which will itself become more of a problem in the coming years: 60-100A at 240V [14-24kW] has been plenty for most households so far, even with a 8-12kW electric shower, but having e.g. an electric shower *and* an EV charger can create problems - both practical and regulatory - and 3-phase makes faster EV charging more practical as well (not that it's needed for most people)... But I don't think even houses being built in 2020 have 3-phase supplies, sadly... ² Energenie: energenie4u.co.uk/catalogue/product/MIHO006 | Loop: www.amazon.co.uk/dp/B00YNCJB3S | Owl: www.amazon.co.uk/dp/B004BDNR84

**ElectroBoom walks in** Owwww!

any option for measuring up to 200a current? can i use different transformer on pzem004t?

I have 7 24v thermal actuator heads. If I had 24v transformer at 1amp, would that be sufficient to power 7 thermal actuators at once, or any combination of the 1-7 powered? Low energy input approx. 3W - 3.5W. • Breakaway current: 0.35A (24V) • 24V can be supplied from either an AC or DC source. • Coil resistance: 24V: 115 Ohms +/-29

Sir, am making homeautomation project based on ESP32 and relay module, project is properly worked. But i don't understand which protocol used. As per my knowledge HTTP protocol for WiFi networking. Am i right sir ? And second question is relay module connect to ESP32 through 10 wire so what is the protocol for this type communication ?

Ironically most modern power supplies are switch mode and have to convert the incoming AC to DC first , DC transmission is more efficient but the technology to convert between voltages at DC wasn't available back in the Edisson/Tesla years so AC was the better choice but now DC would be better.

sounds like a war or battlefield: to avoid any casualties

Please make a video with ATM90E26 and esp32

UK homes only have single phase as standard. Neighbours either side will have the other two phases.