Safely monitor 300v 10A current

[jrichemont]

I have added a mains conditioner to the ring that powers my PC and AMP. I'd like to log (since the fuse has cut out a few times prior (hence this project). Measuring L-N safely is easy; juse use a little torroidial transformer to drp 250vRMS to 6v at 10ma and fiddle with resistors to get the voltagew right. Fully isolated.
Measuring the current being taken by the load safely is not so easy. I can put a low reistance hight current shunt from Lout to the load and this will give me a few mv/ma but still at 250vRMS which is a bit too close to turning my Arduino to a film of solicon oxide. Does anyone have any idea how I can measure current (16A circuit) at 250vRMS withoutuning resistor bridges (right voltage if all works but not isolated ftom HT. I don't think a transformer will cut it because either the tiny voltages/currents across the shunt or I could use one ratedat 16A 250v but that will drop the output to the load significantly; it's supposed to be the load after all, not part of it.

Any bright ideas welcome. Or I just stick to measuring the voltage - but I'd awfully like to know current use too. The idea is to use an Arduino or similar to log these 10x/s even if the power cuts out (microelectronics on battery) so when I restore things I can look back at just what went wrong. Spike on the input? Running the load too close to limits? Who knows but with 24 hours of good data I should be able to find the issue; I do need as much data as I can collect though. Without a visit from the electric utility, preferably.

Many thanks;
Jeremy

 

[ZipZapOuch]

Or a clamp meter if you separate the L and N in your AC cord.

https://www.amazon.com/Klein-Tools-CL220-Auto-Ranging-Temperature/dp/B08CFWMYYY/ref=asc_df_B08CFWMYYY?mcid=a98050b59d9031a78c26eb6fff4ccede&tag=hyprod-20&linkCode=df0&hvadid=693406198453&hvpos=&hvnetw=g&hvrand=17229014308753937118&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9006283&hvtargid=pla-978182831030&th=1

 

[Diver300]

I'm not sure about the battery charger idea; isn't it their job to produce constant current / voltage regardless of input? (to a limit of course but I suspect measuring the output of that would be highly non-linear.

danadak's link was just to illustrate how opto couplers work.

 

[Nigel Goodwin]

I would NOT advise on replacing the 16 amp MCB with a higher rating one. The ring may not be wired with wire of a high enough current rating. A ring main in the UK is normally wired with 2.5mm cable. (The 2.5mm is the cross sectional area of the conductors. )
Les.

My concern isn't the 2.5mm wiring, it's almost certainly wired using that - it's that it's a spur and not a ring, hence the 16A MCB.