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| Shopping for used scope to use as curve tracer |
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| Wallace Gasiewicz:
I was eventually able to get traces on my Agilent digital scope, using an analog BK transistor trace unit. The traces were terrible. I never did get to the point that I was able to find something like a Z axis for blanking the return trace. I do not recall all the adjustments I made to make it work, it was a while ago. It is not as easy as using an analog scope, which the tracer I have was actually made for. It would be great if someone could develop something to do a trace easily on a digital scope. It would let you record and save the various traces. Any old analog scope with X, Y, and Z inputs would work just fine. A DC input must be there also. I think all scopes have a choice for DC vs AC input. Low frequency response scopes would be preferable, so cheaper scope would be just fine, and of course one with a big clear tube screen. There are even old Heathkit scopes without a timebase that would work fine. Storage not necessary. I do not know what output impedance your tracer has, as I recall the old tracers were meant to be directly connected to scope input. So, I do not know if you need a 50 ohm input on your scope for these purposes... The input to the scope is basically a fairly slowly changing DC value, not really any sort of HF signal, so freq response is not important at all. |
| Wallace Gasiewicz:
Just another thought....does anyone have any experience with using a cheap computer based scope for this purpose?? I do not know very much about these computer based scopes at all myself. |
| mag_therm:
1) If the abscissa ( ...I had to spell check it !) on X axis is independent var and does vary linearly with time, the 'scope can be used in normal sweep mode. If scope is storage, then one trace only is needed. For non storage, repeated sweeps of DUT are needed usually with a linearly rising sawtooth, with falling trigger on the flyback. This case covers a lot of engineering problems. Example is sweep of frequency in spectrum analyser. 2) Second case would be with abscissa not varying linearly with time in DUT , when a true XY plot is required. Examples, switching devices and magnetics. |
| wasedadoc:
--- Quote from: Wallace Gasiewicz on August 25, 2022, 09:55:03 pm ---So, I do not know if you need a 50 ohm input on your scope for these purposes... --- End quote --- Not just a case of Octopus type tracers not needing a 50 ohm input. If the scope does have that and it can be switched off, you must do so. If it cannot, find another scope. |
| Electron123:
OK, I'm probably doing something wrong here. The scope doesn't seem to do anything no matter what I do with the octopus (even when I unplug it). I've attached a schematic of the octopus I'm trying to use, a photo of it on my breadboard, a screenshot of what I'm seeing on my scope, and a data dump of the parameters. The power source I'm using is a wall wart with 7.5 VAC, 350mA. The pictures were all taken with the octopus attached to a resistor (DUT). The red and black allegator clips in the breadboard photo are the octopus probes. The black one is connected to the scope's ground terminal. The scope probe next to the red clip is channel 2 and the other is channel 1. I've tried all the suggestions generously provided in this thread. |
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