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Thermal Imaging / Re: Thermal Camera Teardown - The FLIR TAU 320 by Fraser
« Last post by Tomas on Today at 01:57:32 am »
Hi do you have this bord in spare?   
Repair / Re: Another Keithley 2000 repair
« Last post by LapTop006 on Today at 01:55:44 am »
That's normal behavior.

Yep, it's odd if you're used to other meters, but these Keithley's do it. If you look up youtube videos of them you'll usually see this.

You can buy "ghost voltage eliminators" (ex from Fluke) if you really hate it, but it's almost never a problem in practice once you're used to the oddity.
Bio electricity is nothing new, I built a bull shit battery (well cow actually)  in the sixties at school from an idea I got from a book that was a few years old.
Just a few plates of tin separated by cow poo, enough power for a pea lamp to glow.
Main drawback was the smell once it warmed up a bit.

Oh yes, any type of organic reaction for energy (whether fuel, heat, or electrical) is going to produce organic waste, which may be putrid. Disposing of the waste will be another problem to overcome. Of course, any remaining reactivity in the waste is lost efficiency, so the ultimate goal would be a waste substance that is pretty neutral (IDK if this is even possible).
Bio gas is possibly that, you get methane gas plus solid fertiliser and liquid fertiliser both have very little smell (slightly of ammonia) There is a bio gas plant just up the road from me and they spread the residue on the fields around me. All proven technology and probably the way to go, takes farm animal and crop waste and turns it into gas and fertiliser also works with human waste.
Beginners / Re: MOSFETS as voltage controlled gates
« Last post by mvs on Today at 01:51:53 am »
Also, does the LM3914 know when I've attached 5 LED's instead of 10 and use that as a scale?
No, it does not. LM3914 is dumb as bread. You need to define voltage window, LM3914 will make 10 equal intermediate steps.
Then you can decide which outputs to use.

If RHI=1.5V, LHI=0.5V and only 5 last leds are connected, you will get 1.5V, 1.4V, 1.3V, 1.2V and 1.1V thresholds.
EEVblog Specific / Re: EEVblog #1147 - 1 Cent Regulator! That's MAD
« Last post by nctnico on Today at 01:51:39 am »
I keep buying unknown brand chinese stuff from LCSC. Discretes, semis, the lot. Always works. Always in spec. I was suspicious at the start so breadboarded some of the parts. Zero problems.

Don't mind waiting a couple of weeks for snail mail if the price is 1/20th of local suppliers and branded parts.
Better do some thermal cycling testing to see if these parts survive long term. My experience with cheaper parts is not good when it comes to life expectancy. In some cases I've seen a 100% failure rate when installed in the field after less than 2 months.
Microcontrollers & FPGAs / Re: Why dont my pointer works ?
« Last post by nctnico on Today at 01:47:01 am »
I'd use a counter to make sure. Also a pointer to a long (typically 32 bit) will be incremented by 4 bytes. Besides that try to use types (line uint32_t, in8_t, etc) from std_int.
No. Inspecting the firmware is the only way because there might be specific triggers involved. Think about the scope examining a USB stick and network traffic first to look for company names. A crapload of information is broadcasted on networks so there is no need to send anything in order to collect initial data.
The NSA has no way to broadcast some "typical" traffic at an oscilloscope? :popcorn:

And, (b) If you were a boss at Rigol, would you risk being caught doing something like that? It would be the end of the company.
Doing a firmware analysis is infinitely easier than stabbing around in the blind trying to hit something. And if you are worried about b): Huawei and ZTE still exist.
The two PWM generators solution is understood (and most likely will be used in the design that I want to implement), I was just being curious about a hypothetical high resolution PWM channel, if it can be used at least theoretically or are other factors that forces the use of two channels. There are a lot of ns in 100Hz, if one can make a precise PWM signal, will it be OK ?

@Kleinstein: for the practical implementation, I was thinking of these capacitors for the filter, are they OK, (the guy has a lot of parts that may be used) ?

Being that telco GPSDOs are designed to live in quasi/outdoor settings in a wide range of climates (inside of equipment cabinets on poles, the typical siting at a cell phone site) they have to be able to generate that heat in order to keep the oven stable.

Its not an abnormal state, its an oven controlled crystal oscillator.
To add the fine ADC there are 2 options. One is using precision resistors,  the one already at the DAC and another to add the fine part. With some 0.1% accuracy one could get some 8 bit accuracy for the fine part. So the fine part could offer an extra 8 Bit (maybe 9 or 10 at best ) bit resolution. Here it would not even need overlap. The divider only needs to be accurate to the full scale of the fine DAC, not to the full resolution.
The resistors need to be good quality, but no absolute need for a extra precision divider.
Especially with a little more resolution from the coarse part and less from the fine part, the resistors get less critical. Modern µCs can be a bit faster than the old days discrete logic and thus get a slightly high PWM base clock.

The alternative might be to not assume an accurate resistor ratio, but do a kind of internal cal cycle. In this case one would need some overlap, so that the fine ADC would cover some +-2 coarse steps. For the adjustment one would use different combinations to get the zero. From the measured near zero cases one would get a high resolution (e.g. 0.01% range) for the scale ratio between the coarse and fine steps. For the adjustment it helps to have a few overlapping steps, as one would get the fine steps corresponding to some 2,3 or 4 coarse steps and thus some extra resolution. I would expect the adjustment only to be needed rather infrequently, so it does not matter if it takes quite some times.

However the step ratio would likely not be a nice integer ratio like 1 coarse step corresponds to 1024 fine steps, but an arbitray number like 5123.6 fine steps to a coarse one. So when setting a DAC value, there will be rounding errors, though very small. When setting a fixed voltage, one would have that rounding problem anyway, as the steps would not correspond exactly µVs. With the measured ratio it is two scales with some odd size (e.g. 120.6 µV and 0.068 µV). The rounding problem is similar, maybe slight less as the steps can be smaller.

For the offset, I dont think that one would need an analog adjustment. It would be more like a rather crude but fixed offset to make sure one can reach the zero and a little below. The exact numerical zero reading would be corrected numerically by adding to the DAC setting.
A ready made DAC chip like the MCP4921 could in theory be an alternative to a PWM DAC for the fine part. But with the filter already there PWM is easy for the fine part and 12 Bit is easy, even if a simple circuit. In the old days one might have used an DAC to change the fine scale setting to get exactly 1024 fine steps to a coarse step, but today I would prefer the numerical way.

To speed the adjustment procedure and maybe add some resolution it helps if the zero detection it not just a comparator, but a high gain amplifier and an ADC, even if only some 8 bit. So the µC internal ADC should be good enough. It's a little like a Null-meter - low gain accuracy, but high amplification, low noise to detect even small deviations.

A single super high resolution PWM channel is possible too and simplifies the math. The delays from switching are not a special problem here - these only limit the use of the very extreme ends (like < 0.1% or > 99.8%), but this also applies to lower resolution. The coarse DAC needs to be precise to the full resolution anyway, so the demands are the same. There are 2 small downsides to those high clocked µCs: one is they tend to use a PLL clock an this can produce extra jitter that might be visible as extra noise. The other is that those higher speed µCs tend to produce more EMI problems, that might end up as extra offsets / noise somewhere. To avoid interactions, e.g. via ground currents the µC creating the PWM should  not do much else during use.  So even using the ADCs might already be too much.
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