ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Lock-down Thread
by Bill Addiss - 02/27/21 01:16 PM
Northern Tool Recalls Powerhorse Generators
by Admin - 02/25/21 09:49 PM
You will never guess
by gfretwell - 02/25/21 07:48 PM
New tool
by SMOKEYBOB - 02/15/21 04:59 PM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
1 registered members (Scott35), 21 guests, and 20 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 6 of 6 1 2 3 4 5 6
Re: Floating Ground - device being tested or scope? [Re: Potseal] #215867 08/04/15 09:35 PM
Joined: Nov 2005
Posts: 823
J
JoeTestingEngr Online Content
Member
I forgot to suggest a couple of things for your observations:
1.)Check your readings again with your isolation TX unplugged. It helps you see how much your setup is acting like an antenna. If the readings are non-zero(They will be.), try moving the leads around on the table or placing your hands along the wire insulation in various places.
2.) Switch your meter to read frequency if it has that feature. See if you're reading line frequency or a harmonic of same.
Joe

Tools for Electricians:
Re: Floating Ground - device being tested or scope? [Re: JoeTestingEngr] #215873 08/06/15 09:09 AM
Joined: Feb 2013
Posts: 264
Potseal Offline OP
Member
Originally Posted by JoeTestingEngr
I forgot to suggest a couple of things for your observations:
1.)Check your readings again with your isolation TX unplugged. It helps you see how much your setup is acting like an antenna. If the readings are non-zero(They will be.), try moving the leads around on the table or placing your hands along the wire insulation in various places.
2.) Switch your meter to read frequency if it has that feature. See if you're reading line frequency or a harmonic of same.
Joe


Yes, I have noticed the possibility of interference. For example, I will later post a couple images of the wave form shown on my oscilloscope when a nearby LED magnifying lamp is turned on and off. The wave form shape remains the same but the "lines get fuzzy".


A malfunction at the junction
--------------------------------------
Dwayne
Re: Floating Ground - device being tested or scope? [Re: Potseal] #216009 09/05/15 03:54 PM
Joined: Feb 2013
Posts: 264
Potseal Offline OP
Member
Well better late than never...

Scope showing square wave with nearby LED lamp off:

[Linked Image from i62.tinypic.com]


A malfunction at the junction
--------------------------------------
Dwayne
Re: Floating Ground - device being tested or scope? [Re: Potseal] #216010 09/05/15 03:57 PM
Joined: Feb 2013
Posts: 264
Potseal Offline OP
Member
And with LED lamp on:

[Linked Image from i61.tinypic.com]


A malfunction at the junction
--------------------------------------
Dwayne
Re: Floating Ground - device being tested or scope? [Re: Potseal] #221147 01/26/21 12:36 AM
Joined: Jan 2021
Posts: 6
quickspark Offline
New Member
The most preferred scope is to connect normally. Floating the scope is the last thing you would want as an alternative.
You are potentially putting line voltage on the case of the scope and bad things can start happening very quickly, this could impose a risk of life too.

We suggest you look at the wiring diagram and decide where the grounded conductor is and ground the scope at that point. The small amount of ripple you see will not affect your measurement. It is tied to the ground via an external plug.

If you are looking at something on the load side of a transformer you should be able to ground the scope normally. You can ground the scope to the circuit through a light bulb, voltage wise. If it sparks, you are going to have to reconsider your plan of action.

Be sure you have the right ground clips if you are looking at line voltage.
It is best to learn your scope technique with a transformer isolated circuit, preferably at low voltages, like a doorbell transformer or a wall wart.

Electrical companies can provide the necessary advise based on the requirement and concern with the floating ground.


Page 6 of 6 1 2 3 4 5 6

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
pcsailor
pcsailor
Minneapolis, MN, USA
Posts: 21
Joined: September 2019
Show All Member Profiles 
Top Posters(30 Days)
Popular Topics(Views)
275,482 Are you busy
209,385 Re: Forum
196,771 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3