Recent Posts

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Projects, Designs, and Technical Stuff / Re: Brinking Light pattern for maximum attention distance at night

« Last post by LaserSteve on Today at 03:43:12 am »

Nothing Xenon in this thread other then Edgerton's lamp is even close to what I've used for laser pump lamps.  Hungaroflash's technique is to place the tube across the AC power line, and use the wiring inductance to limit current.  Others do that too, picking the trigger point towards the end of the AC half cycle.

Great technique, and I've used it, but the pulse is long, and the lamp fill  pressure is very low,  so the peak energy is low. Thus luminous   efficiency is low.

Steve

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Repair / Re: Keysight 34450A Help

« Last post by floobydust on Today at 03:40:43 am »

Is the ACmV reading stable?
What about different (lower) frequencies. What about linearity - how is it at 25, 50, 75mV; still -5.16% ?

We don't have a service manual or schematic to troubleshoot the ACmV path, and it's a custom DMM IC. Right to repair nah.
The relays are kinda cheap so try working them, I don't think they have a lot of palladium lol. But I think the cmos muxes are doing the range switching work. If it was grossly overloaded on ACmV the H/W could be damaged, that's why I suggest seeing if it's just a span problem or more.

There are two firmware loads - CPU for the main and MCU for the DMM portion and not sure if any F/W update covers both processors.

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Projects, Designs, and Technical Stuff / Re: Emergency stop for runaway large DC motor

« Last post by NiHaoMike on Today at 03:36:59 am »

Assuming it's powered from an AC power supply, have a contactor disconnect the AC power. Switching DC is far more difficult and shouldn't be necessary.

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Projects, Designs, and Technical Stuff / Re: Transistors - die pictures

« Last post by Noopy on Today at 03:36:51 am »

Well the picture of the pcb is a mess. 

But let´s do the semiconductor:

The decapping was done with acid? It seems like there was a two layer metal layer and the upper one was eaten away at most places.

The JFET can easily be seen. There are the thin gate stripes laying above of it. So the substrate is gate.

The upper left bondwire probably contacted one side of the JFET. The schematic says it should be drain.

The other side of the JFET is connected to a resistor and the resistor is connected to the substrate and so it is connected to the gate of the JFET.

In the upper right corner we have a bipolar transistor with shorted collector and base. One side of the diode is connected to the gate of the JFET through the substrate. The other side has no connection. Since the contact is eaten away and the top metal is lost it would be logical that the emitter was connected to the lower right bondwire.

I assume the lower right bondwire is connected to the node between the JFET and the resistor because otherwise it would make no sense and the structure of this metal looks a little strange. That could have been a connection.

All in all we should see a JFET amplifier with a resistor and a diode at the gate. The diode seems to limit the input signal. The resistor for some kind of damping?

That would be my first interpretation.

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Test Equipment / Re: Vevor SDS1104 for first oscilloscope?

« Last post by Muttley Snickers on Today at 03:33:31 am »

If the price is right then a used SDS1104XE in good condition would still be worth serious consideration particularly for somebody on a budget. If the OP is not in a desperate rush for a scope then this would be my recommendation, cheaper than new and far superior to what they are currently considering.

I just saw someone buy a second hand SDS1104XE for 540 bucks+postage on aus ebay, so prices are not going down that much. New one is still close to 700 on AppVision. I think the scope market is just too slow in Australia and some people don't know about 800X series. We are still yet to see 800Xs here. Everybody else has them for sale but not Australia (and our friends across the ditch). Perhaps wait until the end of financial year to get better deals.

It's still way too early to access or speculate on what is considered a fair price for a second hand SDS1104XE in Australia, and even for those updating. In fact, they are probably more likely to hang on to their prior model for a while until they realise that it is no longer needed and only taking up space.

Also, I wouldn't use ebay as a guide as there are likely plenty of buyers whose only focus is the purchase of a good oscilloscope at a reasonable price and perhaps not even aware that there is a new series available. I can speak from experience when I say that not everybody who seeks certain test equipment reads or frequents electronics discussion forums, I never did anyway.

I hate giving out secrets and revealing my sources but the best place to keeps tabs on prices and more importantly find a well looked after pre-loved scope from a reputable person is here, and don't tell anybody else the prices might go up.

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General Technical Chat / Re: Future of computing & ai

« Last post by Doc_white on Today at 03:33:15 am »

I've created and manipulated a series of images based on your descriptions, focusing on visually representing conceptual ideas using bubbles:

1. **Realistic Scientific Illustration**: This image depicts two smaller bubbles inside a larger clear bubble, designed to look realistic and scientific, similar to illustrations found in a physics textbook. It's rendered in high-resolution grayscale to emphasize detail and realism.

2. **Scientific Illustration with Magnetic Fields**: This version includes the two smaller bubbles inside the larger bubble, but with added visual elements representing magnetic fields, similar to a capacitor diagram. This image is also in grayscale and aims to depict the interaction and tension between the bubbles through magnetic field lines.

Both images are designed to reflect scientific and theoretical concepts in a visually engaging manner, suitable for educational and professional use.

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General Technical Chat / Re: Future of computing & ai

« Last post by Halcyon on Today at 03:28:11 am »

What on earth are you on about Doc_white? This all seems like word salad.

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Metrology / Re: Remote controlled DMM DCV INL tester based on voltage divider idea

« Last post by CurtisSeizert on Today at 03:26:26 am »

Ah, you are right. I made some simplifications when I was doing the math, and then I forgot that I had made them. The error of the transfer function at any given point is actually given by this sum:

E(v) = E_t(v) + sum(i = 0 to inf)( (2^i) * Esc(v / (2^i))

Where E_t(v) is the turnover error at v, and Esc(v) is the corrected sum error (as defined previously) at v. This can generate a linear component to the fitted error, which I just compensated by adding an appropriate linear term to ensure the slope between the endpoints was zero. How many terms one needs to calculate to get a good approximation depends upon the shape of the corrected sum function near zero. I did some trials with smoothed cubic spline fits to sequences of random numbers to make random  transfer functions, and four terms was good for simple transfer functions, while six to ten terms were necessary if things were all over the place (i.e., things that looked like 20+ order polynomials).

I tried this procedure with the real data I had from the 3458. When I back calculated the sum error from the transfer function, this gave a linear residual. This should not be possible with a polynomial transfer function, though it could be possible with terms on the order of x log x. Because the area around zero was leading to a large portion of the calculated non-linearity, I tried multiplying the interpolating spline by ( (2/pi) * arctan(a*v) )^2, where a is a horizontal compression factor. I used a=20 so that the effect would be localized close to zero. I attached a plot showing the effect of this. Most of the deviation at the points closest to zero is actually due to the smoothing factor used in calculating the spline. This gave a residual sum error function with a slope of zero. That said, I don't know that this is a good correction to make because the steep slope near zero is a very repeatable observation, so it may be a real thing. Both the turnover error and the sum error indicate some large swings in the transfer function near zero that would be tough to pin on the source. Because the shape of the curve near zero is so influential, it is probably best to get more points in that region.

Anyways, it is possible to use the source, some minimal fitting, and a handful of iterations to derive an INL curve from the measurements, and it is looking good well below the ppm level.

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Beginners / Re: Oscilloscope recommendation

« Last post by CAG on Today at 03:23:52 am »

Thank you for the link. I did originally start this search with a Google inquiry about automotive scopes. The only scope I have used was a snapon branded older (2006) scope. The automated features it had for automotive testing were frustrating more than helpful for me. I really just wanted a couple knobs for time and amplitude and that simple stuff was buried in the software. It really wanted to autoscale everything. Anyway I was thinking of getting a more general purpose scope this time. I read the thread you provided and will do the youtube rabit hole tomorrow. Thanks again!

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General Technical Chat / Re: Future of computing & ai

« Last post by Doc_white on Today at 03:20:10 am »

AI processing my theories in ways I don't calculate right at first and probably need to tweak or figure out how I deal with pairing of bubbles. I believe if one is created inside a bubble a twin is formed. So logically helium has two and if you consider hydrogen a gas it's the second shell to oxygen's core air structure as oxygen. But if oxygen is held in two hands and all the rest double twice and live inside those bubbles it makes more sense to me.

Plus you have the two fields in one bubble that way.

Like the capacitance diagtam.

That's most likely where splitting the atom comes in, splitting two bubbles apart.

To make gas you expand it and then you compress it.

To create life you expand a gas and retract abd like an accordion billions of systems are generated.

The plasma ball that you put your hand on , it's like a way to visualize how God can put his breath similar to the plasma to the bubbles to create the oxygen

Have any of you experimented with crude oil? And extraction of one air bubble by vacuum and cycling that bubble through water centrifugal force vortex sealed system into a copper coil that is designs with traps like this ××××××× so the air pushes through from big bubble to small creating a current a field that is tappable for energy consumption purposes of its own system to start the process that keeps the oxygen oxygen in its true firm floating up in bubbles that will glow like photons into a coil that as I said feed back to the oil. And it's always in a northern bubble facing position so that it doesn't. Contract and become a heavy gas going back into the oil.

I would love to hear from anyone willing to experiment and delve deep into the reasons the government and scientists decided to not go these paths.