I wanted to come up with a way to datalog current measurements of up to 50A RMS, using a current transformer to do most of the conversion and 5VDC-based electronics for the rest. Accuracy doesn't have to super-tight, but if I can get within a few percent and be capable of reading amperages down to maybe 1 amp or less, that would be great.
What I've come up with is below. I scaled the resistor to keep the peak voltage on the secondary side below 5V for a 50A RMS primary current, and also chose the nearest resistor size I could to get an output with simple math. After averaging through the RC filter, the DC voltage at the output is almost 1/20th of the AC RMS amperage (factor is actually 20.19.)
I was wondering if anyone has any thoughts on this approach. Am I re-inventing the wheel? Is there a simpler or better way to get the same thing done? Are there hidden problems here that I'm not seeing in simulation?
One specific question I had is about the rectifier. My understanding is that the current transformer secondary will try to produce a specific amount of current (not specific voltage) and so the rectifier has no effect on the voltage dropped across the burden resistor. The simulation seems to confirm what basic math in a spreadsheet told me, but I'm still not 100% confident that I've got this right.
I also tend to get turned around when converting between RMS, Peak, and Average voltage levels. I'm pretty sure I've got this all right, but I'd love for someone to check my work.
What I've come up with is below. I scaled the resistor to keep the peak voltage on the secondary side below 5V for a 50A RMS primary current, and also chose the nearest resistor size I could to get an output with simple math. After averaging through the RC filter, the DC voltage at the output is almost 1/20th of the AC RMS amperage (factor is actually 20.19.)
I was wondering if anyone has any thoughts on this approach. Am I re-inventing the wheel? Is there a simpler or better way to get the same thing done? Are there hidden problems here that I'm not seeing in simulation?
One specific question I had is about the rectifier. My understanding is that the current transformer secondary will try to produce a specific amount of current (not specific voltage) and so the rectifier has no effect on the voltage dropped across the burden resistor. The simulation seems to confirm what basic math in a spreadsheet told me, but I'm still not 100% confident that I've got this right.
I also tend to get turned around when converting between RMS, Peak, and Average voltage levels. I'm pretty sure I've got this all right, but I'd love for someone to check my work.