I'm working on a project to quantify the power consumed by an AC device. For my example, let's just assume it's running on a 120V/15A circuit.
I'm currently working on the current stage of the measurement circuitry. I am using a current transformer with an appropriately sized shunt resistor to give me a 2.5V to -2.5V AC voltage (5V peak to peak). I am using a coupling cap to remove any DC component. My first go at this was to use a 2.5V DC reference to boost the AC signal to a 0V to 5V range so I can measure the waveform with an MCU (in 30mA increments, theoretically). This is where I am at right now. My question is this:
I am not interested in calculating actual power, apparent power, etc, etc. This is not a metering application, rather an application to give a rough magnitude of current (although I wouldn't mind a certain amount of granularity and the project may creep towards metering over time). I figure if I can feed this 2.5V to -2.5V AC signal into a peak detector, not only can I easily measure the peak level with an MCU (PIC/AVR/MSP), but I can also double the resolution by boosting the AC signal to 5V to -5V (10V peak to peak). Most peak detector circuits I have discovered involve a voltage drop of some sort due to the necessity of a diode or two in the circuit. Is there a way to develop a peak detector without the seemingly requisite diodes? An average drop of 0.5V of, say a 1n4001, is quite a large chunk out of my 0-5V range.
Oh, by peak detector, I mean positive peak detector.
I hope my question is clear. I would welcome any suggestions.
I'm currently working on the current stage of the measurement circuitry. I am using a current transformer with an appropriately sized shunt resistor to give me a 2.5V to -2.5V AC voltage (5V peak to peak). I am using a coupling cap to remove any DC component. My first go at this was to use a 2.5V DC reference to boost the AC signal to a 0V to 5V range so I can measure the waveform with an MCU (in 30mA increments, theoretically). This is where I am at right now. My question is this:
I am not interested in calculating actual power, apparent power, etc, etc. This is not a metering application, rather an application to give a rough magnitude of current (although I wouldn't mind a certain amount of granularity and the project may creep towards metering over time). I figure if I can feed this 2.5V to -2.5V AC signal into a peak detector, not only can I easily measure the peak level with an MCU (PIC/AVR/MSP), but I can also double the resolution by boosting the AC signal to 5V to -5V (10V peak to peak). Most peak detector circuits I have discovered involve a voltage drop of some sort due to the necessity of a diode or two in the circuit. Is there a way to develop a peak detector without the seemingly requisite diodes? An average drop of 0.5V of, say a 1n4001, is quite a large chunk out of my 0-5V range.
Oh, by peak detector, I mean positive peak detector.
I hope my question is clear. I would welcome any suggestions.