10-17-2024, 05:11 PM
Hello everyone,
I came across the Resonance Induction book that comes with the RICK kit from Rick Friedrich, at some point he shows a series-parallel circuit that contains resistors to measure power going through them. His style is such that he gives more questions than answers. I had some coils that I used for some previous experiment and some capacitors, so I gave it a try. At first I didn't measure anything unexpected and wanted to ask here if you guys knew how to do this measurement properly, but then I turned my probes from 10x to 1x and measured the following.
To describe the setup. I have a signal generator that has sine wave at output, 12 Vpkpk, tuned to about 801 kHz frequency to resonance (the resonance changes a bit when I move stuff around). The capacitors are 100 pF, 3 kV, china made, ESR unknown. The coils are 61 turns, .3 mm wire, 25 mm radius, should have about 150 uH. The resistors are 2 W 1 ohm ceramic resistors.
The setup looks like this:
In the book Rick says to measure the power on the resistor on input and the power on the resistor in the resonance circuit. I guess the best way would be to use a differential probe, but I don't have those. So I decided to use ungrounded probes on each side of the resistor, square the voltage and divide by resistance to get power.
And this is what I got on the scope.
The M1 trace should be the voltage over the input resistor, and the M3 trace should be voltage over the resistor in the resonant circuit. The trace shows that the voltage over the resistor in the resonant circuit is about twice the voltage over the input resistor.
What do you think? Is this the way to go about measuring the voltage over a resistor? If so, why is the power in the resonant circuit double of the power over the resistor on the input? If it is not, how to improve this measurement?
I came across the Resonance Induction book that comes with the RICK kit from Rick Friedrich, at some point he shows a series-parallel circuit that contains resistors to measure power going through them. His style is such that he gives more questions than answers. I had some coils that I used for some previous experiment and some capacitors, so I gave it a try. At first I didn't measure anything unexpected and wanted to ask here if you guys knew how to do this measurement properly, but then I turned my probes from 10x to 1x and measured the following.
To describe the setup. I have a signal generator that has sine wave at output, 12 Vpkpk, tuned to about 801 kHz frequency to resonance (the resonance changes a bit when I move stuff around). The capacitors are 100 pF, 3 kV, china made, ESR unknown. The coils are 61 turns, .3 mm wire, 25 mm radius, should have about 150 uH. The resistors are 2 W 1 ohm ceramic resistors.
The setup looks like this:
In the book Rick says to measure the power on the resistor on input and the power on the resistor in the resonance circuit. I guess the best way would be to use a differential probe, but I don't have those. So I decided to use ungrounded probes on each side of the resistor, square the voltage and divide by resistance to get power.
And this is what I got on the scope.
The M1 trace should be the voltage over the input resistor, and the M3 trace should be voltage over the resistor in the resonant circuit. The trace shows that the voltage over the resistor in the resonant circuit is about twice the voltage over the input resistor.
What do you think? Is this the way to go about measuring the voltage over a resistor? If so, why is the power in the resonant circuit double of the power over the resistor on the input? If it is not, how to improve this measurement?