Electronics > Beginners
Maximum Scope Voltage
DigitalAura:
I have recently changed my scope from a Rigol DS1070z to a fully unlocked Keysight DSOX1102G and I've noticed the maximum input voltage is 150v, whereas on the Rigol it was 300v.
Sorry if this is a really dumb question but am I correct in assuming that only applies when using a probe attentuation of 1x? I only ask as I have a 220v inverter I wish to test and figured it best I ask on here first before turning my expensive new toy into garbage. Would it be okay just switching the probe into 10x or would I need to use a high voltage probe for this?
Thanks
Ian.M:
I wouldn't trust a switchable probe for that - one moment's inattention or a buildup of conductive dust in the switch and its bye-bye expensive new toy.
Also scope probes have to be derated for voltage with frequency - usually their rating is flat up to a few KHz or tens of Khz then drops off exponentially with respect to log(freq). This is especially nasty in a HV chopper circuit, where there may be high frequency high energy ringing on edges, so if the inverter boosts to a HV bus then chops that, its almost certainly unsafe to scope the switching nodes of the boost section or output H-bridge. If it uses a line frequency output transformer, its a lot safer - but personally I wouldn't probe the secondary side with anything less than a CAT II rated differential HV probe.
DigitalAura:
Thanks for that, I knew I'd find a use for my differential probe sometime.
tggzzz:
--- Quote from: DigitalAura on October 09, 2018, 02:45:21 pm ---I have recently changed my scope from a Rigol DS1070z to a fully unlocked Keysight DSOX1102G and I've noticed the maximum input voltage is 150v, whereas on the Rigol it was 300v.
Sorry if this is a really dumb question but am I correct in assuming that only applies when using a probe attentuation of 1x? I only ask as I have a 220v inverter I wish to test and figured it best I ask on here first before turning my expensive new toy into garbage. Would it be okay just switching the probe into 10x or would I need to use a high voltage probe for this?
Thanks
--- End quote ---
For either scope you need to use an isolated differential HV probe. Realise that the BNC connector's shield (and hence probe ground) is connected directly to the protective mains earth.
Never ever disconnect the scope's protective mains earth; "floating the scope" can be lethal and can (more or less) subtly damage the scope. And also give unreliable measurements due to the high capacitance!
Apart from that...
Sooner or later a *1/*10 probe will be in the *1 position.
Check your scope probe carefully: the maximum voltage is a function of frequency, and often falls to 30V at high frequencies.
DigitalAura:
I'd never float the scopes earth as I have an isolation transformer. Thanks anyway, that's a lesson I made sure I understood quite some time ago. I was planning on powering the inverter from either a battery or a bench supply so I figured earth wouldn't be a problem.
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