Recent Posts

91

Buy/Sell/Wanted / Re: ̶F̶S̶ : Keithley 2002 8.5 digit like new

« Last post by coromonadalix on Today at 03:33:40 pm »

we ordered many Siglent stuff  gens etc ...  they had at least 1 inch to 2 inches of protection between the item and cardboard exterior, and sadly  some had manipulations,  traces, bumps  etc .. but nothing touched the instruments ...

it was a very poor packaging, plain stupid ...   they did not care about the item value


and now the task to find parts ....  hope you get them ...

92

RF, Microwave, Ham Radio / Re: Quansheng UV5 (new 2024 V5.00.03) wont allow FW change or chirp. Any Clues?

« Last post by radiolistener on Today at 03:30:06 pm »

What should I do with this file?

you can apply it to source code, compile and test it.

Well, here is test version of k5tool which supports new bootloader beacon packet, it uses old flash write packets, so it's unknown if new bootloader supports it. There is a risk that it may not work on a radio with new bootloader 5 (or higher) and it include risk that it may brick the radio, because no one tested it with new bootloader radio. Use it at your own risk.

This test version also includes some minor fixed for write packet structure to be compatible with original flasher software, it will be committed soon to git-hub.

If you test it on a radio with new bootloader, please let me know if it works and share the log file.

93

General Technical Chat / Re: Post a picture of a cat!

« Last post by tom66 on Today at 03:29:49 pm »

Training cats...

It obviously depends upon the cat (some dogs are harder to train than others, no difference to cats), but my experience...

You have to train them when they are young.  Pretty much from being a kitten.  I think it's very hard, possibly impossible, to change a cat's behaviour as an adult unless you have that framework in early on.

Cats are strongly food motivated.  So training them around a reward mechanism seems to work the best.  You can't really train them like dogs where they want to satisfy the owner.  There is no point at all in training a cat negatively (same for dogs), they do not respond well to it, so for instance if they do something wrong like scratching the carpet, don't shout at them, just remove them from the situation and give them something else to do.

Cats are more equal with humans in the hierarchy.  If you treat them well they will treat you well back.  Dogs seem to be more unconditional in their love.  I'm thinking that if you were homeless and didn't have enough food the dog stays by your side, the cat leaves  !

Both our cats can 'beg' for food, respond to their name (return home), walk on a leash, one of ours can even 'high-five' you on command.   Both know the sound of the 'laser toy' (my laser distance measure) down to the button press to turn it on.  They don't scratch carpets or furniture - only their scratching posts.

Dogs are obviously infinitely more trainable but they are completely different creatures requiring daily stimulation and exercise.  I quite like that our cats can get all of their stimulation from going outdoors every day.  Though I know opinions differ on indoor vs outdoor cats.
 

94

Test Equipment / Re: $20 LCR ESR Transistor checker project

« Last post by Davo013 on Today at 03:27:59 pm »

I burned mega328_st7565 to the tester, and that is the only one which is kinda working except that the screen size doesn't fit
i forgot to add the makefile, so i added it to the folder also but.... same problem
I really don't know what to do with the makefile or how to use it, looks like a compiling thing

Did some tests still the same problem with those uF's

I must say that this firmware runs quite smoother

95

Metrology / Re: Solartron 7081 - Reference Circuit

« Last post by Ismsanmar on Today at 03:26:22 pm »

They are indeed Chinese copies, and yes, the insulator is PEEK rather than Teflon.

But, PEEK is perfectly adequate, unless you are making cables for an electrometer, and given the fact that getting hold of the original connectors from Fischer is next to impossible and horribly expensive, the choices would appear to be: butcher the meter and get rid of the Fischer connectors or buy well made copies from China.

Given that Fischer seem not to care about hobbyists needing to find spare parts for their Solartron equipment, I'm more than happy to buy from a Chinese manufacturer who has seen the gap in the market and makes very well machined and finished copies.

What I'm triyin to say is that taking into account how much they cost, going for 30-35€ on Aliexpress, they are not so much less than the last price seen for the original ones:
https://www.eevblog.com/forum/buysellwanted/group-buy-fischer-connector-plug-s104-a053-130/
And this order was made with the option that Fisher offer to the public, with PEEK insulation.

Don't get me wrong. I've bough one of the chinese short version to check how well they are made, and they are ok. They use the same metals, finishes and coatings than the original, but I have some other Fischer connectors and you can feel the difference. Of course, I paid for 1 unit 6€ with coupons and discounts on Aliexpress on the last summer sale, but at their original asking price, they are not worth it.

Since the subject of electrometers and PTFE has been brought up, I should point out that PTFE is not the ideal insulating material when electrometers and little currents are involved. PTFE is triboelectric (scraping on a conductor induces a charge) and piezoelectric (mechanical stress induces a charge). Further, PTFE has a phase change at 19C that causes a change in volume, so if it's constrained, that provokes a charge. A colleague told me about one of his electrometers that had a barbed feed through pin in PTFE that behaved oddly and it took him some time to pin it down to the constrained PTFE and phase change with temperature. Clear perspex is the best stuff for diddy currents.

As far as the Solartron is concerned, PEEK will be just fine.

Everybody that has an electrometer should know that that's not exactly correct. Before I bought mine (Advantest R8340A) I searched information to make my own cables, because the unit that I wanted to buy didn't have any test cables. Here in this forum there are some very good threads on that topic, and at the end if you want to go the "low noise" route, always use the original cables, or those relatively cheap triaxial cables made by keithley (new or used) that are always available on eBay, or use Lemo 001 101. And all of those use PTFE in one or two of the insulating sheaths. The magic resides in the carbon layer.

And don't ask me why, but inside every 8.5 digit multimeter that I know, the connection between the binding posts and the pcb is made with a PTFE coated cable.

I was lucky to find a brand new original triaxial cable for the meter (with both internal insulation sheaths made of PTFE), so in the end all good.

96

Other Equipment & Products / Re: Run Weller W61 for 110V on 220V?

« Last post by Ian.M on Today at 03:17:07 pm »

No.  A diode cuts half the waveform so 50% power, but a US 110V element is one quarter of the (hot) resistance of an equivalent rest of world 220V element (for double the current at half the voltage to get the same power), and at 220V would be overrun by a factor of four, so even with the diode would still be overrun by a factor of two.  Also that would put DC across the magnastat switch which is likely to shorten its life

97

Power/Renewable Energy/EV's / Re: Stability of grids with a high percentage of asynchronous sourcing

« Last post by coppice on Today at 03:15:20 pm »

This islanding is an organizational problem in the worst case.

How is the power not being guaranteed to stop when the grid operator turns it off for maintenance or an emergency an organisational problem? Is your idea of organisational that maintenance only occurs at night, when the sun doesn't shine, and every source can be expected to drop out? Battery storage has made even that a bit dodgy.

98

Test Equipment / Re: High current shunt - temperature drifts

« Last post by CosteC on Today at 03:14:45 pm »

Can you feed the currents you want to compare through the same CT?

No. I am testing CTs. Or Rogowski Coils.
Generally, I need to measure large current and its relation to "small current" or "small voltage". In practice those are two "small voltages" - voltage from shunt(s) or voltage output from integrator (rogowski coil)

But I would like to hear more about your idea. Can you share?

You should just run the same wire through the DUT then several times, and reduce the current significantly.

Not really practical. LV devices have small apertures, and current density will increase when putting more turns as insulation takes space for copper.
For MV devices putting more turns is simply not possible.
Putting more turns causes issues with conductor position location and external fields, particularly important for Rogowski coils.

I know for sure some labs use special lock in amplifiers and moderate current levels, but it is outside my budget now.

99

Microcontrollers / Re: STM 32F4 FPU registers and main() gotcha

« Last post by dietert1 on Today at 03:14:43 pm »

Today something similar happened when i worked on a small Win32 test app (network client).
There were no FPU operations in main(), but some in a thread started with CreateThread(). The app failed with "FPU not initialized" error. I solved the problem using _beginthreadex() instead and it worked. I learned that _beginthreadex() includes necessary CRT initializations.

Regards, Dieter

100

Microcontrollers / Re: STM 32F4 FPU registers and main() gotcha

« Last post by peter-h on Today at 03:13:36 pm »

Thank you both.

I am certainly not using floats before enabling the FPU (which is done in b_main() which then does a long jump to main() which never returns) and I would hope that if I was, it would comprehensively not work

It is probably by accident that main() does not use floats currently. I do have some printf() debug calls in there (printf() being mapped to come out on the SWV ITM debug port) which output longs but not floats. If they were floats, would that matter? I am confused.