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Forum Index : Electronics : Looking for an oscilloscope

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Godoh
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Joined: 26/09/2020
Location: Australia
Posts: 378

Posted: 06:54am 19 Jan 2021

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Silicon Chip magazine had an article about a 1000/1 probe for testing auto ignition voltages. Maybe worth a look for those folk wanting to play safely with High Voltages.
Using an isolation transformer is a good way to use a scope, at least it is possible to then test across components.
The comment about not having the mains earth connected could be worth looking at more. The problem is that the Neutral is connected to an MEN system. The neutral is not just earthed at the switchboard, it is earthed at many points along the transmission system.
So disconnecting the earth on the CRO may not be enough to make it safe. Using a proper isolation transformer to remove the neutral/earth bonding helps.

I think that there were other High Voltage probes in kit forms, maybe from Electronics Austalia if anyone remembers that mag.
Most TV techs have high voltage CRO probes. Maybe not so much in use these days with LCD screens so there may be some cheap ones around too.

I have seen properly isolated CROs used to measure voltage drop across resistors but if they are not isolated from the MEN system you just blow up the equipment you are working on. Earthing a component in an inverter or amplifier does not go down too well. Unfortunately the technique we learnt from Lost in Space of just hitting the whole switchboard with a fire extinguisher and having it come back to life doesn't seem to work.
Cheers
Pete

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