I have never used an oscilloscope and don't know how they work

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  • orientalsniper
    Badcaps Veteran
    • Apr 2013
    • 459
    • USA

    #1

    I have never used an oscilloscope and don't know how they work

    Hello all, so I just bought a DS1054Z (http://www.rigolna.com/products/digi...1000Z/ds1054z/) to help me assist repairing laptop/desktop motherboards.

    I'm basically this right now:



    I could use some pointers or any site that might help me introduce to this new instrument.
  • stj
    Great Sage 齊天大聖
    • Dec 2009
    • 30950
    • Albion

    #2
    Re: I have never used an oscilloscope and don't know how they work

    http://www.ionpool.net/arcade/scope_files/scope.html

    Comment

    • smpstech
      Member
      • Dec 2014
      • 15
      • US

      #3
      Re: I have never used an oscilloscope and don't know how they work

      All I can tell you about Scopes is that careful with what you connect your Ground Wire to on the Scope probe. With SMPS's you can blow stuff up.

      Comment

      • popeye
        Senior Member
        • May 2011
        • 155

        #4
        Re: I have never used an oscilloscope and don't know how they work

        Look for EEblog on youtube Dave Jones site

        Comment

        • orientalsniper
          Badcaps Veteran
          • Apr 2013
          • 459
          • USA

          #5
          Re: I have never used an oscilloscope and don't know how they work

          Originally posted by smpstech
          All I can tell you about Scopes is that careful with what you connect your Ground Wire to on the Scope probe. With SMPS's you can blow stuff up.
          How so?

          Btw, thanks for the suggestions.

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #6
            Re: I have never used an oscilloscope and don't know how they work

            You plug what ever you are working on into isolation transformer (both Hot and Neutral on the output winding are completely floated/not connected to the safety ground).
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment

            • keeney123
              Lauren
              • Sep 2014
              • 2536
              • United States

              #7
              Re: I have never used an oscilloscope and don't know how they work

              We just use to cut off the ground pin that plugs into the receptacle will that not work?

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #8
                Re: I have never used an oscilloscope and don't know how they work

                Originally posted by keeney123
                We just use to cut off the ground pin that plugs into the receptacle will that not work?
                If you touch the chassis of the scope when the probe Ground lead is attached to the primary side of the circuit ground ref. you are working on, the chassis of the scope is now at hot potential and you can be electrocuted.
                Last edited by budm; 12-09-2014, 10:39 PM.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment

                • popeye
                  Senior Member
                  • May 2011
                  • 155

                  #9
                  Re: I have never used an oscilloscope and don't know how they work

                  HI

                  Just watch this. Here

                  Comment

                  • Uniballer
                    Badcaps Veteran
                    • Jul 2013
                    • 334
                    • USA

                    #10
                    Re: I have never used an oscilloscope and don't know how they work

                    Originally posted by keeney123
                    We just use to cut off the ground pin that plugs into the receptacle will that not work?
                    Other than budm's safety objection, this will work on older scopes with linear power supplies. But newer scopes with switching mode power supplies cannot be isolated from ground so easily because they are generally capacitively coupled to the power line. You will need to use a transformer to isolate the unit under test (or scope if you insist) in that case.

                    Comment

                    • stj
                      Great Sage 齊天大聖
                      • Dec 2009
                      • 30950
                      • Albion

                      #11
                      Re: I have never used an oscilloscope and don't know how they work

                      one other thing not mentioned is that most low-end scope probes are only rated for 300v

                      Comment

                      • Compgeke
                        Badcaps Veteran
                        • Feb 2014
                        • 524
                        • USA

                        #12
                        Re: I have never used an oscilloscope and don't know how they work

                        Originally posted by stj
                        one other thing not mentioned is that most low-end scope probes are only rated for 300v
                        My 'scope itself is only rated for 300V and it (was) a higher end Tektronix - a TDS684B.

                        Comment

                        • stj
                          Great Sage 齊天大聖
                          • Dec 2009
                          • 30950
                          • Albion

                          #13
                          Re: I have never used an oscilloscope and don't know how they work

                          ah, but if you have a x10 probe...............

                          Comment

                          • keeney123
                            Lauren
                            • Sep 2014
                            • 2536
                            • United States

                            #14
                            Re: I have never used an oscilloscope and don't know how they work

                            Originally posted by budm
                            If you touch the chassis of the scope when the probe Ground lead is attached to the primary side of the circuit ground ref. you are working on, the chassis of the scope is now at hot potential and you can be electrocuted.
                            If the ground on the plug is cut off so it does not attach to the electrical ground the scope will be floating. We use to have a problem when I work for Gerber Scientific Produces with the a power board that drove a New Hermes Computerize engraving machine. The Lead Research Engineer Buddy Rich cut off the ground plug so we would not blow fuses when we attached the ground clip of the scope. Buddy Rich had attended Harvard and he wrote the loop equation for servo motors. I may not be understanding this right but it would seem this would fix this problem unless they are making the Tektronix scopes different than in the 1980's.

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #15
                              Re: I have never used an oscilloscope and don't know how they work

                              Cutting the Ground of the power plug of the scope will stop the damage (blow the fuse or smoke) to the scope of or what ever you are working on when the Ground probe of the scope (which is also connected to the chassis (safety ground, some time the circuit ground of the scope is connected to the chassis through low Ohm (10~100 Ohms) resistor) of the scope, BUT the chassis now will become HOT, it is safety issue, not the blow up issue when Ground prong of the power plug is cut.
                              If you draw up the SCH of the line operate power supply of the primary side circuit, you will see the current path when you attach the test equipment to the hot side of the circuit, for example the scope probe on the primary side ground ref point which will be the negative leg of the filter cap. It will explain a lot when you analyze the circuits.
                              It is hard not to make contact with scope body when you have to make any knob adjustment.
                              Last edited by budm; 12-11-2014, 11:19 PM.
                              Never stop learning
                              Basic LCD TV and Monitor troubleshooting guides.
                              http://www.badcaps.net/forum/showthr...956#post305956

                              Voltage Regulator (LDO) testing:
                              http://www.badcaps.net/forum/showthr...999#post300999

                              Inverter testing using old CFL:
                              http://www.badcaps.net/forum/showthr...er+testing+cfl

                              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                              http://s807.photobucket.com/user/budm/library/

                              TV Factory reset codes listing:
                              http://www.badcaps.net/forum/showthread.php?t=24809

                              Comment

                              • keeney123
                                Lauren
                                • Sep 2014
                                • 2536
                                • United States

                                #16
                                Re: I have never used an oscilloscope and don't know how they work

                                You may find this interesting. The attached file is from Tektronix and floating grounds. They say the using a isolation transformer is just as bad as cutting the ground plug.



                                Originally posted by budm
                                Cutting the Ground of the power plug of the scope will stop the damage (blow the fuse or smoke) to the scope of or what ever you are working on when the Ground probe of the scope (which is also connected to the chassis (safety ground, some time the circuit ground of the scope is connected to the chassis through low Ohm (10~100 Ohms) resistor) of the scope, BUT the chassis now will become HOT, it is safety issue, not the blow up issue when Ground prong of the power plug is cut.
                                If you draw up the SCH of the line operate power supply of the primary side circuit, you will see the current path when you attach the test equipment to the hot side of the circuit, for example the scope probe on the primary side ground ref point which will be the negative leg of the filter cap. It will explain a lot when you analyze the circuits.
                                It is hard not to make contact with scope body when you have to make any knob adjustment.

                                Comment

                                • keeney123
                                  Lauren
                                  • Sep 2014
                                  • 2536
                                  • United States

                                  #17
                                  Re: I have never used an oscilloscope and don't know how they work

                                  Forgot to upload file.
                                  Attached Files

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #18
                                    Re: I have never used an oscilloscope and don't know how they work

                                    I do not see the attachment, but using isolation transformer with floating HOT and NEUTRAL will be same as working in the cold side of the circuit since the primary side of the product you are working on are now isolated from the incoming AC.
                                    You have to watch out as to what kind of isolation transformer you get, some will have Neutral bonded to the Ground, for example:
                                    http://www.tripplite.com/product/Sta...ansformers/839

                                    I had people telling me that the scope and the unit he was working on was still damaged when using this isolation transformer, I told him that it is not fully isolated transformer, he did not believe so he check the secondary winding and the incoming ground and sure enough the Neutral is bonded to Ground.
                                    I do not float my test equipment, I float what I am working on when the primary side has active circuits that needs to be troubleshoot and with safety ground still present, or I use differential probe.
                                    https://www.badcaps.net/forum/showpo...72&postcount=6
                                    And for critical circuit, I use TOPAZ ULTRA iso Xformer with minimum leakage capacitance, very hard to come by, http://www.ebay.com/itm/like/171145692167?lpid=82
                                    Just think of it when you make the measurement with scope or what ever in the cold side of the circuit, the switching transformer is THE ISOLATION TRANSFORMER.
                                    If you can afford differential probes, that will be good thing to have.
                                    And remember one thing, the ref Ground of the switching circuit in the primary side is not referenced to the incoming/safety ground, it is referenced to the negative leg of the main filter cap. When you work in the circuit, you will look to see how it is designed and how you go about making the measurement.
                                    Circuit ground is not the same as safety ground and depend on the circuit sometime you can tie the circuit ground to the safety ground.

                                    Page 2 of TEXTRONIX:
                                    Floating An Oscilloscope: A
                                    Definition
                                    “Floating” a ground referenced oscilloscope
                                    is the technique of defeating
                                    the oscilloscope’s protective grounding
                                    system – disconnecting “signal
                                    common” from earth, either by defeating
                                    the grounding system or using an
                                    isolation transformer. This allows
                                    accessible parts of the instrument
                                    such as chassis, cabinet, and connectors
                                    to assume the potential of the
                                    probe ground lead connection point.
                                    This is dangerous, not only from the
                                    standpoint of elevated voltages present
                                    on the oscilloscope
                                    (a shock hazard
                                    to the operator)
                                    , but also due to
                                    cumulative stresses on the oscilloscope’s
                                    power transformer insulation.
                                    This stress may not cause immediate
                                    failure, but may lead to future dangerous
                                    failures (a shock and fire hazard),
                                    even after returning the oscilloscope
                                    to properly grounded operation!
                                    Not only is floating a ground-referenced
                                    oscilloscope dangerous, but
                                    the measurements are often inaccurate.

                                    This results from the total
                                    capacitance of the oscilloscope chassis
                                    being directly connected to the
                                    circuit under test at the point where
                                    the common lead is connected.

                                    Bottom line: SAFETY, SAFETY, and SAFETY.
                                    BTW, most of the electronics training hardly teaches about safety Ground and Circuit Ground, most people see the word Ground and think that they are the same, I see that so many times here when asking OP to take the Voltage readings in the Primary side.
                                    Last edited by budm; 12-12-2014, 05:27 PM.
                                    Never stop learning
                                    Basic LCD TV and Monitor troubleshooting guides.
                                    http://www.badcaps.net/forum/showthr...956#post305956

                                    Voltage Regulator (LDO) testing:
                                    http://www.badcaps.net/forum/showthr...999#post300999

                                    Inverter testing using old CFL:
                                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                    http://s807.photobucket.com/user/budm/library/

                                    TV Factory reset codes listing:
                                    http://www.badcaps.net/forum/showthread.php?t=24809

                                    Comment

                                    • keeney123
                                      Lauren
                                      • Sep 2014
                                      • 2536
                                      • United States

                                      #19
                                      Re: I have never used an oscilloscope and don't know how they work

                                      I think this is very useful for people who are learning or who are advance users of
                                      Oscilloscopes.
                                      " I had people telling me that the scope and the unit he was working on was still damaged when using this isolation transformer, I told him that it is not fully isolated transformer, he did not believe so he check the secondary winding and the incoming ground and sure enough the Neutral is bonded to Ground.
                                      I do not float my test equipment, I float what I am working on when the primary side has active circuits that needs to be troubleshoot and with safety ground still present, or I use differential probe."
                                      https://www.badcaps.net/forum/showpos...72&postcount=6
                                      And BudM you are right about not learning this in school. I never learned this in 3.5 years of school nor did I learn it in 15 years as an electronic technician. Isolating the device one works on and not the test equipment is the way to go because the safety ground on the test equipment will protect the operator of any voltage that may make it's way to chassis on the test equipment. Thank you for your input it is of a great value and this is the perfect forum to express it. And I think that measuring the isolation transformers output resistance to ground and also, measuring the output voltage to ground are good procedures to follow. If one reads any resistance or voltage then that is not a isolation transformer, that is resistance less than what would create a potential harm. Any voltage measurement from a ground to either side of the output of the isolation transformer would make that a potential danger.

                                      Comment

                                      • orientalsniper
                                        Badcaps Veteran
                                        • Apr 2013
                                        • 459
                                        • USA

                                        #20
                                        Re: I have never used an oscilloscope and don't know how they work

                                        Originally posted by popeye
                                        HI

                                        Just watch this. Here
                                        Thank you! That helped much, I also appreciate what the others were saying too.

                                        Comment

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