# Proper burden resistor CT clamp

I'm trying to figure out what the proper burden resistor I should use, but the information I'm reading from OpenEnergyMonitor answer for the proper resistor values doesn't match what I was expecting.

So I'm using YHDC SCT013-000, which has a rating of:

• 100A Max current
• 50mA rated output
• 1:2000 turns ratio

I'm looking for a burden resistor that gives me a 3.3 output. So my thought process was to calculate the needed resistor with Ohm's Law.

• 50mA / 3.3V = 66 Ohms

Now on openEnergyMOnitor.org they multiple the output from the clamp by 1.414 (squareRoot(2)). To turn the output rating from RMS to peak to peak. Which if I do that it will reduce my burden resistor down to like 47 ohms.

My question is does that make sense. Are CT transformers usually in RMS vs peak to peak voltage.

current test I've tried the original burden resistor I suggested and it seemed to work at the lower ranges that I was testing. Just don't know if it will fail if the current goes higher I guess. Also curious to understand why there suggesting the conversion.

openEnergyMonitor.org example - https://docs.openenergymonitor.org/electricity-monitoring/ct-sensors/interface-with-arduino.html

• "... they multiple the output from the clamp by 1.414 (squareRoot(2)). To turn the output rating from RMS to peak to peak." Not quite. $V_{peak} = \sqrt 2 V_{rms}$. i.e. The voltage from 0 to peak - not peak to peak. $V_{p-p} = 2 \sqrt 2 V_{rms}$. Commented Dec 29, 2022 at 1:06