Hello all, I'm starting to think ahead about connecting measurement equipment to my SGTC. I have experience with measurement of sub-kilovolt equipment, but not with the higher voltages a tesla coil produces. I would be interested in hearing about the measurement equipment and connections that other coilers have used. Here are options I have thought of or considered. Primary circuit voltage measurement: A potential transformer in series with the circuit is likely to be the most accurate, but it is expensive; and I expect the inductance of the transformer will change the coil resonance frequency. A high-resistance voltage divider (more than 10 Gigaohm?) would be simple to implement, should not change the resonance frequency by any significant amount, and would draw very little current. However I am unsure about what to use as the ground voltage reference of the divider. I use a counterpoise system and I would expect it to have transient voltages which might be large enough to damage voltmeters or scopes connected to it. My other thought is to put in two dividers, one an each output rail, and measure the differential voltage between them, Primary circuit current measurement: The NST current is in the millamp range. The problem isn't the current, it's still the voltage. I could put a microamp meter on the voltage divider try to scale it appropriately. The impediance of the meter might change the divider, but probally not if the divider impediance is very large. The other option that comes to mind is a current-sensing transformer, where one of the primary rails runs through a toroidal transformer which scales the output to the input. I haven't used these before and I'm not sure on the appropriate use. Secondary circuit voltage and current measurement: The topload has something like 300kV or more, and there's not really anywhere to tap into that doesn't effect the circuit directly. My only guess here is remote electrostatic sensing. I have absolutely no idea how to implement or calibrate this. Definately interested in experiences from coilers. Thanks in advance, Joshua -- Joshua Thomas My new email address is: joshuafthomas@xxxxxxxxx Please update your information if you have not already done so.