Getting 2 % is pretty easy, many commercial CT's at 0.3% at the transformer, resistance of the wire from the CT to the load (burden in the electrical world), and all the things that effect voltage measurements come into play. A well designed setup can get to 0.5%.
Thanks to surplus a classic 5A CT can be found for a few $'s. More modern instrument grade CTs are expensive unless you can grab one off the usual auction places. A "classic" 100A or 200A:5A is a good 4-5" square and can be as much as 2-3" thick. Today you don't need the 5 Amps, heck 10-50 mA is good enough, so the size can be smaller. I've been trying to shoot for say 0.1% to 0.2%. Again for 'fun'. Where some more fun comes in is when you get below 10%, that would be 10Amps using a 100A CT. The industry specs stop at 10%. A 0.3% transformer is only 0.3% at full rating (and above). Was just looking to see if anyone has come up with something new / low cost / etc. On Tue, Apr 29, 2014 at 12:06 PM, Brent Gordon <volt-n...@adobe-labs.com>wrote: > Years ago I installed a TED-1000 (now obsolete) system from <http://www. > theenergydetective.com/>. Their software is terrible but the system > works. This system uses two current transformers and a single voltage > measurement system that all go inside your circuit breaker box. I don't > recall the sampling rate (1 KHz maybe). The instantaneous voltage and > current measurements are multiplied, summed, and transmitted once per > second. The data is transmitted to a receiver using the house wiring > (similar to X-10). People have hacked the system to use their own receiver. > > I haven't directly measured accuracy; monthly totals are usually about 5% > low when compared to my electric bill. The software compensates for > missing readings. Resolution seems to be around 10 watts. > > Brent > > > On 4/29/2014 11:25 AM, Pete Lancashire wrote: > >> Next spring I'm going be rewiring my house. And for 'fun' I want to drop a >> couple current sensors on the input side of the main panel. >> >> Being a beginner 'nut', I'm looking for more accuracy then needed. >> >> Voltage, Frequency, waveform will be taken care of later, but accurate >> current has be a bit flustered. >> >> I've been reading up on CT's Iron core and Ferrite, and on Rogowski coils. >> And the many new IC's on the market that take care of a lot of things. >> >> Has someone done this before ? And if so any experiences to share ? >> >> -pete >> >> _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.