Hi,

I am designing a switched mode power supply for a travelling wave tube. In this research my ripple has to be approximately 10mV on a 6kV output. What is the best way to measure this voltage ripple at such low levels? My voltage divider is a 1/2000 ratio, meaning that a 10mV ripple on this will be translated to approx. 10mV/2000 value. The only ways I have came across so far is using a capacitvely coupled op-amp to remove the DC offset (high pass filter) and then amplify the output signal with the op-amp by say again the 2000 ratio so that it is replicated at the output of the op-amp. But is 10mV still too low to detect accurately? Are there any more efficient, accurate ways to perform this measurement?

 

First the 10mV specification is very small. I think 10V of ripple is fine, but I don't know much.
Use a capacitor + resistor to remove the DC from the reading and pass the AC to the meter/scope. Like you said "high pass filter". You should put some protection across the resistor. Maybe to back to back Zener diodes to keep high voltage off you meter/scope or amplifier. At power up and power down the voltage on the resistor can get very large.

I use a scope because I can see 10mV. You may have a problem measuring 10mV near a switching power supply because of noise.