On 23/01/2022 08:30, time-nuts-requ...@lists.febo.com wrote:
Stick with the transformer. The use of a capacitive divider is predicated on the line waveform always being a sine wave. Dream on! All it takes is one good spike down the line, maybe only 20-30V amplitude, and your capacitive divider passes it right on to that ADC that has a much lower (3.3V?) limit. Guess what goes poof? ------------------------------------------------------------------------
Transformers distort the waveform, unless specifically designed for that need.
Many of the commercial monitors, use a fully floating ADC system to sample and digitise the incoming AC (via a purely resistive divider and protection devices.) Then pass that digital data over a HV isolated channel (opto-coupler, or pulse/signal transformer) to other systems for parameter measurement recording and display.
The front end samplers and ADC are powered by an internal AC source (at 10's of kHz) coupled in via a small HV isolated transformer, rectified/filtered/regulated etc to power the incoming sampler. Such things are rated for use on industrial 3-phase systems, not just low voltage (115/230V) systems with full safety approvals.
(For experimental purposes, a battery would probably do. But you'd still need an isolated data transfer channel.)
If you want to "wing it" there are some USB isolator devices, that even pass 5V power (via a built in isolated DC-DC converter.) Conceptually, they could be used to run a small USB 'scope front end input device, if you trust the far east to build the things with enough creapage/clearance distances to maintain isolation in safety...
Or float an entire "sacrificial" laptop, and remote control it via WiFi with VNC for example.
I know a US company on the West coast, that used to (maybe still does) float entire Tek' scopes at many 100's of KV, to monitor the control element waveforms etc in industrial Klystron and TWT test fixtures..
Such 'scopes were "controlled" by extended non conducting control shafts and rod's. 115V/60Hz power supplied by an isolating transformer, where the secondary had a few inches of air space between it and the primary+core assembly.
They were inside the HV PSU rack, behind a non conducting transparent panel. Simple, but worked well.
Regards. Dave G8KBV -- Created on and sent from a Unix like PC running and using free and open source software: _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
