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Low output from Eden WT800 in Bridge Mode

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  • #16
    Originally posted by Helmholtz View Post
    It is not clear how you measured and what - side means. I suggest to post a drawing that shows how you connected the load and your meter.
    Originally posted by Helmholtz View Post
    It is not clear how you measured and what - side means. I suggest to post a drawing that shows how you connected the load and your meter.
    - is the inverted side of bridged output. I have probes on pos and negative outputs. Trying to determine if my stove top heating elements are the same ohms under load per G1 (lemmy) suggestion.
    Attached diagram. As I understand it, I'm measuring RMS voltage across 8 ohm load, and dividing by current measured. (as seen in attached pic).
    Thanks for your replay,Helmholtz.
    Attached Files

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    • #17
      Attached diagram. As I understand it, I'm measuring RMS voltage across 8 ohm load, and dividing by current measured. (as seen in attached pic).
      Ok, clear so far and correct. I understand that + and - denominate the hot terminals of left and right outputs in bridged mode. There is only one voltage and one current. What caused the confusion?
      - Own Opinions Only -

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      • #18
        Originally posted by Helmholtz View Post
        Ok, clear so far and correct. I understand that + and - denominate the hot terminals of left and right outputs in bridged mode. There is only one voltage and one current. What caused the confusion?
        I have a scope lead on either side of load to observe inverted, and in phase sinewaves. When I move the DMM to measure current on negative side of load, the signal that was inverted is now in phase. Why would it do that? The DMM can't invert signal, can it?
        Hope this is clear.

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        • #19
          Originally posted by Stan Keith View Post
          I have a scope lead on either side of load to observe inverted, and in phase sinewaves. When I move the DMM to measure current on negative side of load, the signal that was inverted is now in phase. Why would it do that? The DMM can't invert signal, can it?
          Hope this is clear.
          Sorry not clear. Current on both sides of the load resistor must be the same. Please show how you connected the scope. I assume you use two scope probes connected directly to right and left outputs?
          - Own Opinions Only -

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          • #20
            I think in this setup with the 5-Amp Variac, it's core is saturating, since your amp at full power is pulling too much current thru it. What did you measure unloaded in Bridge Mode?
            Logic is an organized way of going wrong with confidence

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            • #21
              Originally posted by Stan Keith View Post
              I have a scope lead on either side of load to observe inverted, and in phase sinewaves. When I move the DMM to measure current on negative side of load, the signal that was inverted is now in phase. Why would it do that? The DMM can't invert signal, can it?
              Hope this is clear.
              I just downloaded the Tek 2430A manual, and what I don't see is independent DMM connections. I'm lead to believe the DMM function is being made via the scope probe leads. I didn't read thru the manual closely....does this have a Ch 2 & C4, which also serve as the DMM inputs? If they're not floating, as an independed battery powered DMM would be, it may be shorting the Right Ch output. If you have an independent DMM to measure the AC current with, as shown in your diagram, then there shouldn't be phase shift.

              Tek 2430A Scope User's Manual.pdf

              Read thru the manual, and....unless I'm mistaken, it does NOT have an independent floating DMM like some of their earlier scopes had (Tek 465, 475 had such an option decades ago). And, only two vertical channels, so you're getting the math processing power for scope measurements.
              Last edited by nevetslab; 03-27-2020, 01:29 AM.
              Logic is an organized way of going wrong with confidence

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              • #22
                Originally posted by nevetslab View Post
                I think in this setup with the 5-Amp Variac, it's core is saturating, since your amp at full power is pulling too much current thru it. What did you measure unloaded in Bridge Mode?
                I think it's impossible to saturate a transformer core by AC load current.
                - Own Opinions Only -

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                • #23
                  Originally posted by Helmholtz View Post
                  Sorry not clear. Current on both sides of the load resistor must be the same. Please show how you connected the scope. I assume you use two scope probes connected directly to right and left outputs?
                  switching DMM to negative side makes otherwise inverted number 2 sinewave in phase with sinewave 1.(shown in attached picture)
                  Scope leads are consistent. probe 1 on pos, and probe 2 on neg.
                  Just curious why it would do that it's still just in series with everything. Should be the same waveform, right?
                  Vielen Dank!
                  Attached Files

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                  • #24
                    Originally posted by Helmholtz View Post
                    I think it's impossible to saturate a transformer core by AC load current.
                    Well, if Stan's output voltage has fallen to 113VAC at full power, when I had 120V at low current, we're causing voltage sag. Maybe Saturation is the wrong term here? (sorry about that)
                    Logic is an organized way of going wrong with confidence

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                    • #25
                      Originally posted by nevetslab View Post
                      Well, if Stan's output voltage has fallen to 113VAC at full power, when I had 120V at low current, we're causing voltage sag. Maybe Saturation is the wrong term here? (sorry about that)
                      That would be voltage drop across the winding's DCR.
                      - Own Opinions Only -

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                      • #26
                        Originally posted by Helmholtz View Post
                        That would be voltage drop across the winding's DCR.
                        Ah....of course. My mistake.
                        Logic is an organized way of going wrong with confidence

                        Comment


                        • #27
                          Originally posted by Stan Keith View Post
                          switching DMM to negative side makes otherwise inverted number 2 sinewave in phase with sinewave 1.(shown in attached picture)
                          Scope leads are consistent. probe 1 on pos, and probe 2 on neg.
                          Just curious why it would do that it's still just in series with everything. Should be the same waveform, right?
                          Vielen Dank!
                          I don't see a reason why the phase of one scope channel should jump if you leave both probes connected to left and right outputs. Maybe some trigger instability. If the two outputs would actually be in phase, current would be zero.

                          BTW, there is no reason to not connect the probe grounds to the amp's ground. Just never connect probe grounds to one of the (hot) output terminals.
                          - Own Opinions Only -

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                          • #28
                            Originally posted by Helmholtz View Post
                            I don't see a reason why the phase of one scope channel should jump if you leave both probes connected to left and right outputs. Maybe some trigger instability. If the two outputs would actually be in phase, current would be zero.

                            BTW, there is no reason to not connect the probe grounds to the amp's ground. Just never connect probe grounds to one of the (hot) output terminals.
                            Force of habbit with me. Ground-referrences the scope to the amp. So, I too am confused with Stan's connections. With an independent floating DMM (battery pwr'd meter), this would work.
                            Logic is an organized way of going wrong with confidence

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                            • #29
                              Originally posted by Helmholtz View Post
                              ......If the two outputs would actually be in phase, current would be zero.....
                              ^^^^^^That! It almost has to be a triggering/measurement error of some kind. If phase was actually flipped on one side making the two outputs in phase, there would be no voltage drop across the load. I don't think that is the case, is it?
                              "Yeah, well, you know, that's just, like, your opinion, man."

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                              • #30
                                Originally posted by nevetslab View Post
                                Force of habbit with me. Ground-referrences the scope to the amp. So, I too am confused with Stan's connections. With an independent floating DMM (battery pwr'd meter), this would work.
                                Yes, the DVM is a battery powered unit I'm using to measure current.
                                I obviously need to read manual, and gain a better understanding of the tektronix's operation.
                                I've always used the RMS display on scope to measure amps output into load. Seems fairly accurate when cross checked with a good DMM.

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