Add support for optional second clamps

So, some devices have dedicated circuits in most electrical panels. It would seem very useful to have the option of connecting a second pair of clamps to the Sense monitor. An alternative to a second set of clamps going on the load side of a breaker in the panel could be an external accessory that plugs inline to 15amp receptacles (connected via wifi).

Once the secondary clamps are installed on a device, Sense would benefit from having that truth value (whether or not your furnace circuit is drawing power) to learn what your furnace looks like on the main clamps.

After installing the secondary clamps, the user would be prompted to identify the single appliance on the circuit using the community labels. Once Sense has gathered enough information about that device, the user can be notified that they can now move the secondary clamps to another device specific circuit and start over again.

Obviously, there are flaws in this approach:

  • someone may not know there are other devices on a circuit that aren’t supposed to be there
  • some appliances have secondary loads, for example condensate pump on a furnace with an cooling coil
  • some devices typically only found on circuits with multiple other loads, so the inline “clamps” plugged in between the device and 15 amp receptacle would be required

I asked for something similar, but not quite the same.
I wanted a third set of sensor clamps for batteries. I realise that there may not be a large enough market for this, however, if they could be used for this or your requirement, then it may be doable.

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How about if you could plug specific devices into a smartplug that reads power to that device, and Sense could make sense of the additional data ?

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Smart plugs aren’t going to work for hard wired or non-NEMA 5-15R styles like a tesla, dryer, stove, etc, so that’s where i thought adding a second set of clamps ( a sensor their system is already setup to use) would seem like a low cost option, assuming it’s easy to add another connector to the PCB).

I guess there’s the question of how much effort does it take to integrate into someone else’s smart plug vs offer their own, but yes, a smart plug integration would be ideal for small appliances.

I’ve been meaning to ask for this as well. So I second your suggestion! I have a couple 5hp irrigation pumps that I would like to track their usage as a farm tax deduction. However sense has yet to ID them. So if I could have a clamp on that dedicated circuit I could track it that way.


Expanding on this idea, I would like to suggest a expansion module. It could support a number (8x) of additional CT clamps which would then be identified and labeled. These clamps would be used for both additional panels (parallel 400A service) as well as specific dedicated breaker devices. Examples include : water heater, range, furnace, ac, pumps, etc.

This would generally negate the need for multiple Sense units within the same building and for aggregating data between multiple units.

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The real question is what do you want the auxiliary CT’s and expansion unit to be able to to do:

  1. Identify multiple devices on the second service or on circuit branches (1MHz/channel)?
  2. Monitor power / energy usage on circuit branches (2Hz/channel)?
  3. Monitor power / energy usage on 240V devices ? (2Hz/channel)

If #1, then the expansion module would likely need to have the same sampling (ADC) capabilities that the current Sense monitor has on a per CT basis. 8x the CTs would require a device with 16M sample rate, plus probably an 8x scaling of of the rest of the hardware as well, plus perhaps a bump in the Wi-Fi bandwidth capacity. The Sense probe is much more complex than just a simple meter. It samples at 1MHz / channel, does a fair amount of arithmetic on the results, does data reduction and communication with the mothership, plus plays a role in triggering identifications. Bottom line, there is no cheap “expansion module” if you want identification on the additional CTs.

If #2, then the question would be what value would those additional channels provide ? Option #2 might help with manual identification of devices by isolating device waveforms on a specific circuit branch. But that setup wouldn’t really help with learning device.

#3 would be useful for learning individual 240V and wired 120V devices. A good accompaniment to smartplugs for 120V devices with plugs.

Added to product with launch of Flex Sensors and DCM in October of 2020.

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