I am new to electronics and the use of an oscilloscope. I have read several threads about the dangers of floating an o-scope. I own a Rigol DS1052E o-scope. I've noticed that the BNC ground on the two channels are tied together (no resistance), however, there is 4.2k ohms between the channel clips and the earth ground lug.

Is this o-scope floating?

Would it be permissible to probe the AC outlet with this o-scope?

I assume it would be dangerous to do so with an o-scope that is ground referenced (as you might clip the ground lead to the hot wire)?

Is it counter-productive to wear an anti-static wrist strap while working with an o-scope regardless of the type of o-scope?

  • \$\begingroup\$ 4.2k is not floating but low enough to avoid ground circulation currents. When you touch a grounded instrument, you are discharged so reducing any risk of discharging to CMOS. THis only makes the wrist strap redundant when doing that. It does not generate static, so it is not counter productive. \$\endgroup\$ – Sunnyskyguy EE75 May 5 at 1:20
  • \$\begingroup\$ Except for special oscilloscopes that are designed for isolation all the scopes I have ever used have the input grounds (BNC ground) connected to the AC power ground pin so they are not isolated. If you are testing equipment that could have its ground at other than AC power ground it needed to be powered via an isolating transformer. When measuring low level signals (e.g. audio) there could be AC power noise injected via the grounding system. \$\endgroup\$ – Kevin White May 5 at 3:28
  • \$\begingroup\$ The 4.2 K will reduce mains 110V to about 26 mA. So, I'm guessing this is limited to prevent nuisance tripping of any RCCB in the mains wiring. Do not connect anti static wrist straps without proper resistors here. Resistors in antistatic straps should be in the order of megohms (current limited to well below 100 uA). \$\endgroup\$ – Indraneel May 5 at 10:39
  • \$\begingroup\$ Thank you for the responses. Learned from each. I did not realize that the wrist straps have high resistance to ground, so I was concerned. Checked mine at 1meg which makes total sense. \$\endgroup\$ – AA9MN May 6 at 19:12

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