I don't know why is that so, but there is a problem if the case is connected to earth in socket and you try to measure floating voltage with probe (like + goes to 12V and GND goes to 5V). This makes short between 5v and earth and coused/destroyed one of the bypass transistors in the supply
The unit under test was push-pull smps for 12v input,supplyed from regulated (now dameged) supply with adjustable voltage/current limit and scope being connected to primary CT of smps with probe GND, + was unconnected.
The unit under test was push-pull smps for 12v input,supplyed from regulated (now dameged) supply with adjustable voltage/current limit and scope being connected to primary CT of smps with probe GND, + was unconnected.
What kind of scope you have?
Only scope I've used with an earth grounded "-" lead was an ancient DuMont.
Only scope I've used with an earth grounded "-" lead was an ancient DuMont.
Hi
Well one is Tektronix 2235 and other one is LeCroy 9400A and Instek GOS658. LeCroy is digital scope.
Well one is Tektronix 2235 and other one is LeCroy 9400A and Instek GOS658. LeCroy is digital scope.
Hmmm, other than a special adaptor that allows differential measurements, I can't think of any advice 😕
The scope's I've used were all either B+K, HP, Hickok and that one little DuMont.
The scope's I've used were all either B+K, HP, Hickok and that one little DuMont.
Hi
Seems to me like all do have this "problem". The only solution I see is no to ground (earth) the scope, but then I would tuch the case of it
Seems to me like all do have this "problem". The only solution I see is no to ground (earth) the scope, but then I would tuch the case of it
You hit it on the last one- it's for safety. If the grounds were isolated, some fool would measure the waveform across a 1 ohm resistor in a 500V B+ feed. As he reaches over to change the vertical sensitivity, his hand touches the case of the scope.... ZAP. RIP.
A floating diff amp is pretty easy to cob together. And it won't kill you.
A floating diff amp is pretty easy to cob together. And it won't kill you.
Hi
The A-B mode is not an option since I need both channels at the same time, and why I would use isolation xformer if this could be already done in/with scope.
I still don't see the logic in channels gnd connection to case.Case is suppose to be only for safety if something goes wrong inside of scope, like phase gets loose and tuches the case of scope.
Hi SY
The A-B mode is not an option since I need both channels at the same time, and why I would use isolation xformer if this could be already done in/with scope.
I still don't see the logic in channels gnd connection to case.Case is suppose to be only for safety if something goes wrong inside of scope, like phase gets loose and tuches the case of scope.
Hi SY
Then how can you do that??
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