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Test Equipment / Re: New Rigol DS1054Z oscilloscope
« Last post by k8943 on Today at 07:10:40 AM »
Thanks guys.

Hadn't seen that it's possible to dim the grid without turning it off. Nice.

I think it would help a lot if I could turn down the room brightness as well ;)

btw. what principles does the scope follow when AUTO setting memory depth ?

Is it worth, on average, leaving it on a manual setting?

ps alsetalokin4017 in your first post certain screenshots channel 4 appears at two levels of time scale on the same screen. How does one achieve that?
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Pt100 tends to need 4 wire connection, while PT1000 might still get away with 2 wires.

With the expensive wire based resistors PT100 tends to be slightly more accurate. With thin film sensors the problem is more with the contacts and thus with slight favor for PT1000. The other advantage of PT1000 is less sensitivity to thermal EMF - the advantage of less aging at high temperatures is with PT100, but not relevant here. Also cable insulation is easier with PT100 - but this is more like a high temperature problem too.

Self heating and noise are the same, if the same power is used - these two are points one can choose the balance.

Both types work, I would slightly prefer PT1000. However there might be better offers on precision PT100s. I would look for ready made probes, not just a bare sensor.

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Beginners / Re: Transformer winding
« Last post by MrAl on Today at 07:07:13 AM »
Thanks AI.


Will not be using Aluminium for sure. Now about the size of the wire for the primary. What is the difference with the gauge of 22 and 16. isn't 16 more space taking as that is more thicker ? Moreover i will be filling the remaining window with the secondary with 2 or 3 Gauge flexible copper wire whichever is available here. probably 3 or 4 turns if possible to get the max current out of it.

Question is if am drawing that much current at the secondary would that heat up the primary with a thin wire like 22 AWG wire ? or would the sweet spot be 16AWG ?

Hi,

Yes #16 will take up more room than #22, but if that was the only consideration then why not use #34 wire as that takes up less room than #22.

The whole thing is based on how much room the primary takes plus the secondary, and because there is a relationship between the primary turns and secondary turns  for both voltage and current, this creates a situation for optimization of primary and secondary wire sizes.  Once you pick the primary wire size you know the secondary wire size because you know the primary voltage, secondary voltage, turns ratio, and thus you know the secondary current.
For example, if you use a wire size for the primary that has cross sectional area 1 unit and the current is 1 amp and voltage 10 volts, then if the turns ratio is such that the secondary is 1 volt then the second current is 10 amps.  This means you know the wire size for the secondary as it must have a cross sectional area of 10 times that of the primary, which would then be 10 units.
What this means is that we know the primary size and secondary wire size, and we then proceed to see how it fits on the core in the window area.  If it fits perfectly then we've optimized the design for the given input voltage.  That gives us the maximum current output on the secondary.  If it is too large  we have no choice but to lower the primary wire size which then makes the secondary wire size smaller too.  If it is too small then we know we might be able to increase the primary wire size (and thus the secondary wire size also) but there is a catch and that is if we get too close to the max going up even one wire size may go over the limit of the window area so we have to back up and call the first try the optimum.

So to recap, once you choose the primary wire you know the secondary wire size, and then you can try to figure out if it all fits in the window, and this will result in three possible cases:
1. It fits perfectly.
2.  It goes over the window area limit.
3.  It does not use up the whole window area.

Depending on the case you may or may not try to increase or decrease the primary (and thus secondary) wire size.

Because of skin depth you also dont want to use too big of a secondary wire size.  1/4 inch diameter is probably a good limit.  If you need heavier wire, use two turns wound bifilar.
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Beginners / Re: DIY X1 High BW Passive Scope Probe
« Last post by StillTrying on Today at 07:04:29 AM »
"Define "High BW".
If you mean 100 kHz, then fine, maybe."


Well I'm already up to 30MHz, actually twice that if you ignore the terrible ringing above about 45MHz.

"or the very high capacitance of the coax cable"
I'm getting around that by not using a coax cable.  :)

"I hope you don't feel like I'm poo-pooing your idea."
Not at all, I've read masses of the probe stuff over the years, I know it's a daft idea.

"... or it is so crappy that its poor performance has completely slugged the source"
LOL
CH1(yellow) is the scope probe switched to X1 for comparison.


pcab.gif
My 0.5m of 'special unshielded cable' surprisingly doesn't seem to have any worse noise pickup than a 1m scope cable on X10.


px10amp.gif
Is mostly self explanatory, With the scope probe on X10, CH1 is the highest I can go without the 20MHz BW limit coming on. I think there's quite a bit of 40-70MHz ringing adding and subtracting from the true CH2 amplitudes.

I'm afraid you'll be disappointed to know I'm just using a hand plaited 0.5m 3x 7/0.2, 1 signal and 2 gnds. It's something I've been going to try for years over twin core or twisted pair, it seems to have good possibilities for a X1 probe up to about 35MHz.
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Repair / Re: Fluke 87 IV - repair log
« Last post by frenky on Today at 07:03:07 AM »
@Phil:
I was really happy to see that pcb is completely clean and that contact corrosion did not affect it.

@Bushougoma:

From what I have read online model 87 IV is completely different from other 87-? models. "87 IV" was later re-branded into Fluke 187.
87IV does have logging capability and also IR for safe serial communication with PC.

Super cap is Panasonic GC5.5V0.10F:


Full resolution:
https://i.imgur.com/BrqZR7f.jpg
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Projects, Designs, and Technical Stuff / Is QSKL/OSKL a manufacturer?
« Last post by analogo on Today at 07:02:31 AM »
There are plenty of cheap converters around labelled QSKL (or is it OSKL). Is it the name of the manufacturer?

Other businesses are selling them as their own all over the world, for example this USB step up converter from DROK at <https://www.amazon.com/gp/product/B00C93Z8JY> but also plenty of smaller shops on Aliexpress or eBay.

In other cases, for example Adafruits' small boards, those sellers would sell clones without the name. Why don't they do that with QSKL?
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Suggestions / Re: Magnetic phone cable
« Last post by eugenenine on Today at 07:01:58 AM »


It works just like Apple's MagSafe system.

So it will catch fire too?
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I don't think its a case of downloading a "library" more of individual library parts/symbol/component.
They are relatively new on the scene and my experience of using their ecad wizard is that although the part creation was good, there are several problems I encountered with the symbols and components. Certainly requiring additional work by me after importing into my CAD package.
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Tried it on an MSOX3000:
 - it automatically shows the cursors when enabling the measurements
 - It sets the measuring point somewhere in the middle of the screen
 - It does show the correct min and max statistics only if you scroll around in the waveform (see above)

Picture:

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Repair / Re: Fluke 87 IV - repair log
« Last post by saturation on Today at 06:57:47 AM »
... or use NiMH AA;AAA LSD cells as required, they rarely leak.  9V rarely leak too, but with increasing poor manufacturing by made in China you never know.  LSD cannot be made too poorly else the recharging and self discharging qualities would disappear.  A good charger would recognize the bad battery and reject it before it went too far bad.

Only 9V ruptures I've seen are occasional reports on the net.  Typically it pictures a failure of the 9v subcells to vent discharge byproduct gasses gently, leading to a subcell rupture, then a rupture of the 9v jacket.  If the subcells leaked without rapid gas discharge it often does so into the outer jacket and contains it from contaminating your powered device.
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