Novice question - 475, what mode is this?
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That's "MIX" - mixed mode. What it does is instead of intensifying the part of the trace to be expanded by the B timebase it simply switches to B timebase at that point of the sweep, wherever you set the delay control.
On the left you are going at at the slower A sweep on the right it actually is intensified but since the sweep is faster it needs that. Push the intensify button and you'll get the whole trace of the slower sweep where the sine waves look compressed but right where the B sweep starts in mixed mode it will be intensified. Looking at the mixed mode tell me that the intensified portion will only be a few cycles - a small version of what you see on the right. Then of course when you go to B sweep the whole screen gets the delayed part - which is currently on the right in mixed mode. I hope you got that, sometimes I am not the best explainer in the world. The manual might do better, not sure. I am not sure of the usefulness of mixed mode, I can't think of a case where I would use it. Well effectively, I like playing around with such things so it is useful for that...:-) |
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On Thu, Jun 21, 2018 at 02:29 pm, Bob Albert wrote:
Sounds like you are not seeing the left side of the trace. Couple possible reasons for this, one is that the brightness or pedestal on your monitor is set too low. There are monitor test programs for this, as it is hard to tell just where black is black but none of the grays are black. One such program is called ntest.exe, which is totally stand alone, would run off anything, like a CD or stick or whatever. One of the patterns is exactly for that and says adjust until you see some particular block in the pattern. That should eliminate any black clipping. Another possibility is if you have an edge lit LCD monitor. As the viewing angle changes vertically in those, the brightness changes. This effect varies, some models are better/worse than others. Some are terrible and you only get a limited range or it does all kinds of funky crap like show a negative image or all the color disappears if you are too low or high, things like that. The one I got - ntest.exe, is from Nokia. If you can't find a suitable program I can upload it or you can hit me up with an email and I can send it as an attachment in a reply. |
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On Fri, Jun 22, 2018 at 10:56 am, Mike Merigliano wrote:
I meant Bob's computer monitor. If LCD which most are these days, some are not quite perfect. My 23" on my good old PC, I think it is an Acer has great viewing angle, about like a CRT. But my laptop which has an edge (bottom) lit LCD is not so good. |
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On Sat, Jun 23, 2018 at 06:13 pm, Dmitri Shuev wrote:
Should help, but that jitter might be settings. If B sweep has an auto trigger, turn it off. Also switch it to DC coupling and turn off any low or high filters. Adjust the trigger level slowly and at some point it should be stable. Hopefully. If not, it is probably some caps somewhere. Nice scope, a coworker used to have one like it. He didn't use it all that much, I used my old trusty 422 much more. In consumer electronics even on the 20V/div scale you can tell 5V, 12V, -12V and all that. I let it freerun and literally used it that way, then when I got to switchers and whatever like the HOT, HVOT or LOPT then it is triggered. And the 422 has a good enough trigger circuit to lock to almost anything. I don't know if yours has tunnel diode triggering but as far as I have seen it is the best. A 422 will lock onto noise, I shit you not. Put music to it and you'll see things you have never seen. If switching to manual DC not auto trigger doesn't take care of it let us know. I'll RTFM and see if I get any ideas. |
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Hello Dimitri,
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To you and all, first of all, apologies if my answer is maybe mission the history (your previous messages) but I'm writing from my phone and couldn't let this go. Itseems no one mentioned or asked you about the following, and it may explain (or not) this - so called -ghosting. To which function the DM44 multimeter on the top is set. If it's on function Time, or 1/time, the ghost you are seeing can be, maybe, the alternate delay controlled the the DM's 44 delta time control. To rule that out, just make sure the DM44 is set to function Volts, Ohms or Temperature an tell us if the ghosting disappears. Or else, keep the Time or 1/time selected and check if the ghosting changes or moves, as you turn the delta time knob on the DM 44, while keeping everything else constant. If the ghosting moves, then what you're seeing maybe nothing more than the DM44's differential delay time measurement, which when activated in conjunction with the MIX function can turn the display quite confusing, as they (the time and 1/time measurement functions) are meant to be used in conjunction with the "A Intense" and the "B Delayed" horizontal modes. In that case, I suggest you download and read the manual of the DM44 option itself, and understand how this ingenious function is meant to work. Brgrds, Fabio On Sun, Jun 24, 2018, 19:47 Jeff Urban <JURB6006@...> wrote:
On Sat, Jun 23, 2018 at 06:13 pm, Dmitri Shuev wrote:Should help, but that jitter might be settings. If B sweep has an auto |
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Hello Dmitri,
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Fabio here again, On my last message, I was mistaken about the DM that ou have. I looked at it briefly on my mobile and thought it was a DM44, but it's in fact a DM43. I`m not sure how the time measurement on the DM43 is done (as it doesn't have the second delta-time knob as I suggested) and I`m not sure if it alternately displays the main delay and then the delta delay, or if it only displays one of them at a time. So, the ghosting in your case, may not be related to the Time measurement function of the DM that I guessed but still, depending on how the DM43 does its thing, it MIGHT be related... so my advice to further troubleshoot this ghosting may still apply. Make sure the "Time" function of the DM43 is not engaged and see if the ghosting goes away (from your pictures, it's difficult to tell if you have the time function activated). Also, on your second picture that you suggest the ghosting is present even on a "simple trace"... well, it's not really as you think... You may have turned the delay time multiplier knob all the way Counter-ClockWise, so that you "suppressed" most of the display of the Main Time base (the slower A time base), but as we can see from the pictures, you're still running on MIX horizontal mode, with the A and B time-bases set at 2 different speeds (A slower and B faster) so, for all that matters, there's no difference for the scope, between the working conditions on your first picture and on your second so, no surprise that it displays the same weird artifacts.. What could really tell something in regards to whether the ghosting effect is present on a "simple" trace or not, is to set horizontal mode to A (lock knobs) only, move the B time base knob to the locked position (with A), and set the A time base to the same speed that you have the B on your pictures. The suggested setting above will really disable the "B" sweep and, if the ghosting disappear, we may discover that the problem is linked to the operation of the B Delayed Time base, OR, if if it doesn't disappear, then we're looking at some problem that is common to both the A and B sweep modes; maybe on the triggering circuits. KRgrds, Fabio On Sat, Jun 23, 2018 at 06:13 pm, Dmitri Shuev wrote:
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Mike Merigliano
5:37am #149175 "Okay, but I did not think the posts about the Tek 475 had anything to do with Bob's computer, so I would have never guessed this." Hmm, the quote function didn't work... Anyway, I saw the left side, what he posted made it sound like he didn't. That's the only reason I mentioned it. I will be watching this thread to see what happens about the B trigger. Also what Fabio said is totally new to me, the meter set to time can affect the triggering ? Seems odd to me but there are plenty of things much odder. Knowing how Tek designs stuff there must be a good reason for this interaction. |
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Hello Jeff, regarding your comment quoted below,
As I mentioned, I was not quite sure about the DM43, but on the DM44 (that has differential Delta time measurement), what it does is alternating 2 different delayed sweeps (one controlled by the o'scope's main delay time base multiplier, and the other, controlled by the Delta time knob (on the DM44 itself) so, yes, it really triggers the B sweep at 2 different points of the A sweep. The net result is that, when you are in "A Intens" horizontal mode, you have 2 intensified segments (and not just one). When you switch over to B Dly'd horizontal mode, you see the 2 delayed sweeps superimposed on the screen, which you turn the delta time control to make them coincide. You read directly the time difference on the DM44's display, in the same unit as the A sweep time base / div. While the display works great and is fairly consistent on both the "A Intens" and "B dly'd" modes, it gets confusing when you are in MIX mode (all that with the DM44). As I learnt a bit more about the DM43 operation, It seems it doesn't superimpose on the screen 2 delayed sweeps at different delays (as the DM44 does) and I think it's safe to assume now that the artifact that Dmitri is seeing is not linked to the DM43's time measurement (but again, it wouldn't hurt to make sure it was not set to that function, to rule out the DM43 as a possible cause). KRgrds, Fabio ..., AlsoHello Jeff, |
Jeff Urban
Fabio Trevisan