Backup Power Capacitor


#1

When the AC power stops for a brief power outage the sense monitor loses power too and when the power returns the monitor has to reboot. Sometimes the power will drop again in a few seconds and on my little computers (raspberry pi) the flash memory cards often get corrupted. I don’t know if the sense is subject to power failures but having a super capacitor to keep the sense running for several seconds and provide a safe shutdown when the power fail exceeds the energy available in the super cap.


#2

The question in my mind is: does the Sense device use its ‘power circuit’ connection for ‘sensing’ or does it solely use the input from the “clamps” (and solar, if one has it)?

If that ‘circuit’ is just 240 power, could it be on a UPS device? (such as one might have for networking devices.)


#3

This is a great suggestion, @keithmclaurin. I believe this would be what our hardware team refers to as a “giant honking” capacitor, which may be challenging to fit inside the current small form factor of Sense, but they’re always up for a challenge, so I’ll make sure they hear about it!

And you’re right, @Dan.C.

Sense does monitor voltage on both legs through the 240v service, and I believe a UPS could inadvertently smooth and shift some of the small variations in magnitude, phase, and frequency that Sense depends on for device detection, but I’ll ask the engineering team to be sure!


#4

The sense uses the AC voltage of each mains circuit and the current from the clamp sensors to determine the power. If you connect the sense to a voltage source that is different from the actual voltage on the main lines then an error in the power calculation will result. The sense I have reports Mains power levels and the corresponding voltage. When I have a 1500 watt load on one main circuit the sense sees the voltage drop from 120.1 Volts to 118.8 Volts. On a recent power outage I had to connect a backup generator to the house and the sense could see the frequency was 61.2 Hz and when the load increased to about 80% the generator frequency dropped to 59 Hz and the line voltage drop from 122V to 115V. This is a very capable sensor system.