Tricking A Smart Meter Into Working On The Bench

When the widget you’re working on is powered by a battery or a USB charger, running it on the bench is probably pretty safe. But when the object of your reverse-engineering desire is a residential electrical meter, things can get a little dicey.

Not that this elevated danger level has kept [Hash] from exploring the mysteries presented by smart meters. Still, with a desire to make things a little safer, he came up with a neat trick for safely powering electrical meters on the bench. [Hash] found that the internal switch-mode power supply on the meter backplane was easy enough to back-feed with a 12-volt bench supply, rather than supplying the meter with the full 240-volt AC supply it normally gets when plugged into a meter base (these are meters for the North American market, where split-phase 240-volt is the norm for residential connections.) But that wasn’t enough for the meter — it powered up, but stayed in a reset state without fully booting. Something more was needed to bring the meter fully to life.

That something proved to be a small AC signal. Normally, a resistor network divides the 240-volt supply down to about 3 volts, which is used by the sensing circuit in the meter. [Hash] found that injecting a 60-Hz, 600-mV sine wave signal with about a 3-volt DC bias into the sensing circuit was enough to spoof the meter into thinking it’s plugged into the meter base. The video below has a walkthrough of the hack, and some nice shots of the insides of the meters he’s been working with.

[Hash] has been working with these meters for a while now, and some of the stuff he’s learned is pure gold. Be sure to check out his 2021 Remoticon talk on meter hacking for all the fascinating details.

23 thoughts on “Tricking A Smart Meter Into Working On The Bench

    1. Get ready for higher bills. The local city utilities company replaced my old style meter with an RF smart meter ~4 months ago. The new one reports energy usage in 15 minute granularity. My electrical bills immediately went up relative to prior years of the same month. It’s about 15% increase for me.

      1. Mechanical meters slow down over time. The “smart” meter holds calibration much better and will not slow down. You actually have to pay for what you use. Don’t like it you can disconnect, or just don’t pay your bill and they will disconnect for you.

  1. Here in the UK just yesterday I was told by a meter reader that, even if I had a smart meter, he is required to come round and read/inspect the meter every 6 months “for safety” (but I suspect really to ensure it has not been tampered with).

    1. Yeah, right. I don’t recall seeing an elec/gas meter reading person in the last 9 years, since we moved in. Certainly not in the last 6 years. I’ve seen the water meter guy a couple of times, but that’s understandable.

      1. He said it was an Ofgem (energy regulator) requirement, and he does indeed come round every 6 months – same man. I have an indoor meter, not in an externally accessible door, maybe that’s why? Or maybe it varies by region?

  2. The problem with smart meters (well, one problem) is that they can’t be easily verified.

    The mechanical meters can be calibrated once at manufacture, and then you’re pretty certain that they work reliably if they’re not tampered with.

    For the smart meter, how accurate are they? Does the program have subtle bugs? And if there are bugs, are they infavor of the customer or the electric company?

    I understand the convenience of remote access and being able to read the meter from the road and such, but the actual measurement should have been kept mechanical and the smartness part would only read the mechanical numbers. That way the customer can be assured that the amount of the bill matches the amount of energy actually used.

    So far as I know, no one’s measured their actual usage using other means in order to compare the numbers. I’m certain there’s a huge scandal there waiting to be uncovered.

    1. These meters are calibrated in manufacture like mechanical meters were. Mechanical meters can last a long time, but can also be subject to substantial drift under certain conditions. Smart meters can be recalibrated and tested with similar equipment. Moving parts don’t generally make anything more accurate, especially over temperature…

      One issue is how they respond to harmonic content (which can goof with mechanical meters as well) but using electronic meters for revenue metering in an industrial context is 30 year old tech at this point.

      The power metering itself is usually done with an ASIC designed for the purpose — the code is interfacing with the chip, but generally the programming in these meters aren’t doing the power calculation math, as it’s a bit intensive to do that way. Used one of these chips for a project once…putting high end components to support it, I could get staggering accuracy for the cost of the part, competitive with bench test equipment. (I am referencing AD’s ADE line.)

    2. Our initial smart meter deployment had significant bugs. If the current was sufficiently distorted (eg, many smps) the reading was incorrect. After investigation it turned out this issue was in favor of the customer, narrow current peaks were not counted and not charged.

      Wouldn’t surprise me if there are many such problems. With a bit of luck they average out with some benefiting the consumer and some the grid operator…

    3. I work in the meter shop at a utility with 50,000 plus meters. I was part of the change out from electromechanical to digital metering. Out of the 6000 plus mechanical meter installs we spot checked we found about 100 that were incorrect, some due to human error some due to broken meters, but we didn’t find a single meter that was in error in the favor of the utility. It is true that electromechanical meters work for a long long time, some of the meters we removed were installed in the 50s, and 99.9% of the meters audited were within our utility spec of 99.98% to 100.02 percent registration)
      With the new AMI (automatic meter interrogation) system with the ‘smart’ meters our system flags meters if there is anything wrong with them and our shop goes out and replaces them in a few days or faster. This stops our billing department from having to estimate the bill based on usage from last year for the same time frame. The meters also are constantly checking their adc’s and all other internal components for mis operation and alert alert the utility if there is a problem so we can change the meter. Out of 60-70k meters installed and retired and changed out we had our first adc failure about 2 weeks ago, the meter was registering at full speed backwards, like the customer was generating power.
      To the person above that was talking about meters catching fire, I don’t know how that would work, I have seen 100s of melted meters from a hot socket connection, a hot socket is a meter base that has ‘jaws’ that have worn out and lost their temper and don’t have enough spring tention to safely pass the required amperage through the meter stabs. I have seen plenty of meters that have been through fires, house fires, farmers burning fields, wild fires that burned poles, but in every one of those cases the meter has melted but not actually burned. We actually had on in our shop for a time that liked like a Dali clock, totally melted but not burned.
      I personally check any functional meter that comes back to our shop and out of the 500-1000 or so I teated in the last 2 years I have yet to find one in error in the favor of the utility, I think I have had 3 in the last 2 years that got retired due to 98% registration, that’s 2 percent off in favor of the customer, and those were 3 phase meters, and the 2% was on one of 3 phases, so I guess technically the meters were 99.906% accurate but got retired anyway.

      I see a lot of scared people and a lot of disinformation about ‘smart’ meters. Something to consider is our utility has been using solid state meters for 20-30 years without any problems, and literally the only difference from a solid state meter and a smart meter is a wifi card in the smart meter. ( our AMI system used 900 mhz Insted of 2.4 or 5.8, so as not to mess up customers wifi, that’s the band that the 90s cordless land line phones worked on.)
      Now with our AMI system we no longer have 20 meter readers driving around reading meters 40 hours a week. Something you may find interesting is that we had an AMR meter system before AMI, and the majority of those were read by a meter reader in an airplane. We used those meters for remote farm pumps, or cell towers in difficult areas to access due to mud or snow or customers that were unfriendly with tall fences and ill tempered dogs.

  3. We had a dumb meter get stuck one time. Had to call them to come replace it.

    I see smart gas meters with little expanded metal shielding in yards where dogs chew on them. Because of course plastic with nice easy to chew edges

    And I’m told my father in law once had to explain he threw something and broke his old dumb gas meter 🤣

  4. In the fine print of the Smart Meter notification of installation letter they had an opt out option. This option I took cost $10 bucks a month for manual reading. Some guy keeps calling to change my mind and install this electronic Big Brother, I have ignored every call he had made. The locked gates and unfriendly meat eating wolf in the backyard and deterred any unauthorized property entry.

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