GordonThree wrote:
so it's sensing line voltage and current, using nothing but a current transformer? that's pretty cool. how does that work exactly? voltage is a potential, so what's the other reference?
No, has terminals for AC line AND the CT.
Uses the AC voltage to power the unit (IE "self power") then reads out the voltage plus reads the voltage across the CT.
I should note to folks who have never worked with CTs, they ARE transformers. The AC wire you put through the center of the core is effectively the Primary which is equivalent to one turn.
The fine gauge wire wrapped around the core creates the secondary and is the output.
Two types of CTs, one is swamped and one is not.
Swamped CTs have a RESISTOR in parallel with the secondary windings.
Non swamped DO NOT HAVE A RESISTOR BUILT IN.
The resistor is there to preload and pull down the voltage of the secondary to a safe voltage.
Non Swamped CTS CAN DEVELOP HIGH VOLTAGES across the secondary which can be lethal with no load attached!
Although these CTs most likely have a swamping resistor, one SHOULD TREAT THEM AS IF THEY DO NOT!
HANDLE WITH CARE!
Best practice is to always ensure the power source has been safely disconnected when working with CT secondary connections..
The back of these meters ARE fully open and you have live line voltage, it IS wise to mount these with some sort of electrical enclosure like you would with a AC outlet or light switch.
