I am looking for a meter to measure true power. Many meters claim to measure active power, is this the same value?
there are 3 different types of power. Real, reactive and aparent power. Real power is known as Watts, reactive as VAR, and aparent as VA. True power is Watts. True power is the electricty that does the work. I've not heard of active power. you might be thinking of RE-active power. When you use your multimeter to measure ANY type of power it is always aparent power, known as VA. (volt amps) All multimeters measure Aparent power. They cannot measure just Real or just reactive. You would need a Watt meter to measure that. You can calculate one uknown if you know the other 2, its known as the power triangle. So if you know Watts and you measure your VA with a multimeter you can figure out reactive power, VAR. I know its confusing. In short. When a meter says it measure true power or RMS power its really measuring apartent power, period. In order to measure just Real/true power you need a Wattmeter.
Yes its the same, but you got some very in depth answers for your question
A meter to do this would need to measure voltage and current simultaneously, and not just the magnitudes, but the angle between the two. The relationship between true power and apparent power is called the power factor. Reactive power is the power used to energize the system's capacitance or magnetize a system's inductance. Capacitance or inductance displaces the voltage vector with respect to the current vector. Do you know ELI the ICE man? As far as meters, a Dranetz 4300 or similar, not new but used with the amp clamps, voltage leads and software, would be a couple of thousand dollars. I don't know of cheaper devices to give both quantities simultaneously.
Yes, it is. All circuits contain some degree of inductance and capacitance in addition to resistance. In a normal circuit, on alternate half cycles, the inductance and capacitance take and return power to the source. They are called reactive loads. (Of course, if you are charging a capacitor bank, they only take power until you are ready to use it.) Resistance only takes power and can usually be thought of as the actual work being done. That power is called various names but the consistent denominator in them is a reference to actuality or activeness. It is measured in watts while reactive power is measured in volt-amps (and, as that implies, includes the true power as well as the moving back and forth power). However, reactive power (and current) is physically real even if not thought of that way and circuits have to be designed to carry it back and forth, not just with the true power in mind.
