Measured a 230vac to 15V/0.1A transformer with A oscilloscope, but it is showing 50Vpp

Thread Starter


Joined Jan 20, 2017
Hi every one.
I have a step down transformer on that it is written as follow
primary : 230v ac
Secondary: 15V ac 0.1A
I connected a oscilloscope across secondary, it is showing 50V peak to peak. How this 50v peak to peak is related to 15v which is indicated on transformer


Joined Jan 8, 2017
The peak value of a sine wave is root 2 (1.414) times the RMS value. So 15 volts RMS has a peak value of 21.21 so the peak to peak value would be 42.42. As your transformer probably had no load on the secondary its output would have been a bit higher than when it was supplying it's rated current. It is also possible that your mains input voltage was higher than 230 volts which could account for the higher value than expected.