I keep thinking about your question based on that very busy meter picture you provided; and also what I keep hearing from the Sense folks about the data the system requires.
It seems to me tht the way the Sense unit is designed it has way too much data rather then not enough. It is possible to flood an AI system with data to the point that it just has way more than it needs.
Perhaps what the system needs is a “tuner” that controls how much data the system actually looks at. FOr example. I see lots of 3, 4, 5 and 10 Wats things going on and off in my system. Almost all of those are LED lights. The system already knows what those are because it can access my Hue lighting data. SO suppose I could adjust the system to ignore fluctuations below a certain value so it could concentrate on just the larger power items.
Moreover, there is really no need for such a high sample rate for the data. We are dealing with a nominal 120/240 volt 60 Hz system. A sample rate of 120hz would be adequate to gather all the data required, but to be certain perhaps over sampling at something like 1Khz would give lots more data than you need. In a 60hz system there is not much going on between cycles.
If you reduce the “noise” data collected that the Sense unit must look through you will have reduced what it has to look at to only the more significant changes. In fact it is pretty clear the the Sense unit is looking at wattage changes at the sub watt level as some of my devices at idle only use about .5 watts and the system can report that. For detection of installed devices that level of data is not really required.
In any case I do not expect this thing to b perfect; I only expect it to do what I was told it would do by the marketing. I am happy to help develop the AI for the system; but in the meantime those who are trying to use this need some relief.
Thanks for considering the screenshot of my home’s electronic pulse …
I think you are right - there probably is more smart “tuning” Sense could do to squeeze out only the most important “transitions of interest”.
As for sampling, at a top level you are right - a 120Hz sample could be used to measure the power if three things were true:
Sense could align the sampling directly at the peak of the 120Hz power waveform (see below). But line frequency drifts so sampling requires continuous readjustment (see @dave’s cool posting that shows line frequency drift here)
Current was always in-phase with voltage - but it’s not. Motor and transformer displace current in one direction and capacitive loads pull the current waveform in the other, meaning real power (current x voltage) changes with different phase.
And Sense only needed power / current / voltage to do identification. But it needs information like phase angles and probably things like estimated relaxation constants for transitions. Those require detailed sampling. You’re just not seeing this data on the transitions because it’s hidden behind a slick UI.
The picture below show the simple case of AC power, when both current and voltage are in-phase. Things get much more complicated when:
Current and voltage are not in phase
Current is not a nice sine wave - all the time in real life.
I’m an electrical engineer, and I think Sense has done a good job hiding all the ugliness behind complex AC measurements that I once had to do in lab. They may have made it so simple that users don’t even realize how hard AC measurements of power really are.
I understand what you are saying but I really think that you are adding layers of unnecessary complication with this approach. We face a lot of the same issues with facial recognition. This was especially true in picking out faces in large moving crowds. What we discovered was that we were giving the system too much data. TO see a face the system does not need a lot of specifics that might individualize a face to pick it out of a crowd for identification. It only needs that level of data once is can see a face and is asked to identify a particular person or count how many individuals it can see.
You have the same problem. Sense needs to see and identify that there is a device before it can possibly individualize that device. Only then would it need all this individualizing information and data that you are describing. But in your approach you are asking it to do both step all at once. So naturally it spends weeks/months/ maybe even years gather this data. Because the graininess is so fine; it may never see enough correlations to decide on what it has found. You are asking it to do too much.
If you simplify this to a multi step process it would work much better. First identify the bounds of a paired on/off event. You might even wait to see that same sort of event more than once. But the point is first to identify that there is some kind of device. Then you can step it up a bit and either tell the user that you found something a let them identify it; or go to the next level and start examining the details of that particular device signature.
I actually think Sense did things the way they did to grossly reduce the amount of data used to do identification and classification, in order to keep the data upload volume within bounds. The monitor filters for just the transitions of interest, then sends just the “features of interest” for each transition, plus a 2Hz stream of power readings to the Sense mothership. But extracting some of those features of interest takes a MHz level of current/power sampling.
ps: I’m not a Sense employee so some of this is speculation based on a few clues Sense has given over the years.
Sens should own up that it CAN NOT identify individual devices in all user environments. That said, I am really happy with the Sense instrument. It is a good value for the buck considering how sensitive and accurate it is. Before I bought the Sense device, I was sceptical of this “Device ID feature” and didn’t hold out any high expectations. My main concern is with my newly installed HVAC heat pump system and propane usage. I am lucky to have selected a HVAC system that tracks its own energy usage. I am able to sum out the HVAC with the rest of the home devices. Summer should be interesting when the new DC ceiling fans kick in.
