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General Chat / Re: The disruption of disruptive technology (Uber)
« Last post by metrologist on Today at 10:30:29 am »
Well, MS is developing a system that will eliminate the need for cashiers. That would have a large impact on the employment rate, if it does create demand for a different skillset and job market - same with the imminent driver-less trucking industry. I kind of like the idea of being able to run into a supermarket full tilt, grab whatever I want, and just leave unimpeded by some kind of payment process. I really despise waiting in lines. Perhaps the catalyst that is driving that are political decisions, such as raising minimum wage making the fixed costs too high. SF wants to impose a 'robot' tax to help mitigate this kind of change, but then Cupertino wants to impose a $1500 per head tax on large companies such as Apple.

I don't think anyone would argue that change should not or will not come, but these kinds of wild politics have wild consequences. We'll see where the trade rift and potential boycotts end up.
Vintage Computing / Re: Macro Shots Of Vintage Mainframe Board
« Last post by rdl on Today at 10:21:55 am »
Not exactly the same thing, but for legal and other purposes, automobiles are often considered antique at only 20-25 years old.
2005 was the last time I was involved with the design of continuous mode PFC boost converters (500W to 3kW) and SiC schottkys were only just then becoming available. The difference was like day and night and it was kinda annoying that I had accumulated all these mad skillz with these beautiful lossless passive resonant snubbers and so much of it had become redundant. My vote it use a SiC schottky and see how you go.
Beginners / MESR 100 v2 leads
« Last post by Noidzoid on Today at 10:12:03 am »
Hello one and all
Could someone tell me why the leads that came with this meter are so short (I'm assuming there is a reason), and is there any reason why I shouldn't change them for something longer with probes on the end rather than the cumbersome alligator clips that are difficult to use in small spaces.
Sorry if this is a dumb question but I really am quite new to this.
Many thanks in advance to anyone shedding light on this.
Incidentally, I find it synonymous better, if in the forum asked technical on-topic questions should also be answered in his thread.
My understanding of X-rays when I read about it as a kid in the 60s was that you had to knock an electron from an inner shell, and then all the outer shell electrons moved in to fill the gap. The change in energy state when shifting orbital layers radiated X-rays. If that description is still accurate then there must be a lower limit of energy needed to dislodge that inner electron so you wouldn’t be able to produce lower and lower energy, longer and longer wavelength radiation. There must be a lower limit somewhere.
Your technique is very interesting, but I don't understand why you refer to "periodic phase noise."  It isn't noise; it's a signal arising from the application of an AC electric field, and it's frequency and amplitude are largely determined by the experimenter.  It isn't really appropriate to equate it to the underlying phase noise of an oscillator.

To be honest, the terminology is a mess - part of the joys of interdisciplinary discussion :)

I have usually referred to it as periodic phase variation/variability but I keep seeing it referred to as period phase noise, too. I'm still trying to get a grip on the terminology used in your area.

What I really call the different contributions to the signal are collective oscillatory motion and random motion. There is a third collective linear motion, too, due to phenomena such as settling or convection. There are a few millions of particles each contributing to the phase. It is assumed that they all move with the same velocity in the applied field, hence collective. Each particle contributes individually to the random noise. The phase difference function, f(tau), simple calculates the phase difference (duh!) across one cycle of the electric field many times starting at a fixed point on the field, t0. i.e., f(tau) = <phi(tau + t0) - phi(t0)>. In the original version of this technique, the phase difference is weighted by the amplitude of the signal, too. This is to compensate for when the amplitude goes to zero at which point phi is indeterminate. Today I don't bother since for my experiments I get less noisy phase difference functions without the amplitude weighting. The signal very rarely approaches zero amplitude. The phase structure function is f(tau) = <[phi(t + tau) - phi(t)]2> (i.e, the second moment of the phase difference) It isn't synchronized with the field and the random noise does contribute. Because it isn't synchronized you don't need a priori knowledge of the frequency (which you do need for the difference function) and, hence, you can determine the frequency as long as the random noise isn't too dominant. The structure function can be constructed synchronously but the equation is a bit more complicated.
I am looking at RM303 / ZT303 that should be similar in performance.
is there an ANENG equivalent for this model?
It does not look like there one yet.
If I read the specs correctly 60mA range is also missing like Q1.

Just get the ANENG 860B+, it's the one to get!  :popcorn:

I don't have an 860B+ but I still think you might be right. Neither of the 2 870 I bought held up to 120v mains and basic accuracy testing. That's pretty bad despite accuracy being pretty good. The Q1 has a neat screen but that's about it for that one. I bet that relay dies WAY before you'd expect too.
Repair / Re: Troubleshooting a scope bought off ebay
« Last post by Haatveit on Today at 09:51:38 am »
As far as I can tell the only time any text would display is if you are in the Measurement mode, and it'll show the time, or voltage, between two cursors. Are you sure they aren't visible in Measurement mode, maybe they have been moved off-screen (if that's possible)? do the indicator lamps around the Cursor/Measurement area work?

This is something that could prove difficult to troubleshoot, however it's not critical for the functionality of the oscilloscope. It's a handy way to measure time and voltage, but you can always do that by looking at the graticule and your scope settings as well, it's just less convenient.
Yeah, those apc smart ups's they have set the floating voltage ridiculously high (29V if I remember correctly?) by default,
it can be lowered in some menu.
Had to replace the batteries on a couple of 19" units after 5 years of mostly standby use and maybe a handful of discharges.
The batteries where already completely deformed and swollen and took brute force to get them out.
I think apc's idea on this is that costumers should replace battery's every two or three years, $.
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