>"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
>news:omutsc54285t4rt5g7cojq0ct5ipqml0be@4ax.com...
>> Yes. Ground everything as often as possible, on a PC board or in a
>> system.
>>
>> Use differential signals when you have to.
>
>Differential is no panacea.
I didn't say that it was.
>LVDS has about the same noise rejection as 5V
>CMOS.
But can run 10x as fast, uses much less dynamic power, and, done
right, has far less jitter.
>
>One cannot escape their obligation to consider, and preserve, the voltage
>between signal and ground, no matter how many signals or polarities one
>uses!
>
>(One of these days, I'm going to need a coax connector not firmly grounded,
>and it's going to have better CMRR and EMI than anything else, despite how
>terrible that sounds. Just takes a little logic.)
Our high-voltage pulse generators use floating BNC outputs,
transformer coupled. That help for really long-distance ground loops.
There are no panaceas. You've got to think.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Reply by ●October 1, 20172017-10-01
On Sunday, October 1, 2017 at 10:47:49 PM UTC+11, Cursitor Doom wrote:
> On Thu, 28 Sep 2017 23:15:51 +0000, Steve Wilson wrote:
>
> > Good to know. Thanks. I don't like to deal with HCl, and I almost killed
> > myself with H2SO4. I will never deal with it again, and I used HCl only
> > rarely and under severely restricted conditions.
>
> It all depends on the concentrations involved. For some reason it seems
> to be very difficult/expensive to source pure Hydrochloric (Muratic) Acid
> whereas 98% Sulphuric is commonly and cheaply available in the big DIY
> stores and plumber's merchants (although probably not for much longer
> thanks to some of London's very stupid/evil morons.
> The one acid that I won't go near is Hydroflouric. That is *seriously*
> nasty stuff indeed; real 'horrorshow' if I may borrow the term from
> Anthony Burgess.
It gets into the flesh and rots it. The fluorine chemists in the Melbourne University chemistry department were an unhealthy-looking bunch with a separate lab up on the roof where they weren't likely to poison anybody.
Part of their emergency kits was a bunch of hypodermics loaded with some calcium salt which had to be injected into any fluorine burn, to lock down the fluorine as insoluble and innocuous calcium fluoride. They weren't supposed to inject it themselves, but to take it over to the university hospital. The kit also included a colour re-print of a Lancet article on what happened if you weren't quick about - I never saw it but it seems to have been designed to frighten the doctors into doing the right thing quickly.
I don't think we lost a graduate student when I was there.
--
Bill Sloman, Sydney
Reply by Tom Gardner●October 1, 20172017-10-01
On 01/10/17 12:47, Cursitor Doom wrote:
> On Thu, 28 Sep 2017 23:15:51 +0000, Steve Wilson wrote:
>
>> Good to know. Thanks. I don't like to deal with HCl, and I almost killed
>> myself with H2SO4. I will never deal with it again, and I used HCl only
>> rarely and under severely restricted conditions.
>
> It all depends on the concentrations involved. For some reason it seems
> to be very difficult/expensive to source pure Hydrochloric (Muratic) Acid
> whereas 98% Sulphuric is commonly and cheaply available in the big DIY
> stores and plumber's merchants (although probably not for much longer
> thanks to some of London's very stupid/evil morons.
> The one acid that I won't go near is Hydroflouric. That is *seriously*
> nasty stuff indeed; real 'horrorshow' if I may borrow the term from
> Anthony Burgess.
Classic CD ignorance, /completely/ misunderstanding what he
is quoting! Clearly he has never read A Clockwork Orange.
"Horrorshow" in Burgess' Nadsat vocabulary means "good", derived
from the Russian word хорошо (xorošo, “well, good”)
(But HF /is/ seriously nasty stuff)
Reply by Cursitor Doom●October 1, 20172017-10-01
On Thu, 28 Sep 2017 23:15:51 +0000, Steve Wilson wrote:
> Good to know. Thanks. I don't like to deal with HCl, and I almost killed
> myself with H2SO4. I will never deal with it again, and I used HCl only
> rarely and under severely restricted conditions.
It all depends on the concentrations involved. For some reason it seems
to be very difficult/expensive to source pure Hydrochloric (Muratic) Acid
whereas 98% Sulphuric is commonly and cheaply available in the big DIY
stores and plumber's merchants (although probably not for much longer
thanks to some of London's very stupid/evil morons.
The one acid that I won't go near is Hydroflouric. That is *seriously*
nasty stuff indeed; real 'horrorshow' if I may borrow the term from
Anthony Burgess.
--
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protocols constitutes acceptance of this condition.
Reply by ●September 30, 20172017-09-30
On 1 Oct 2017 00:03:32 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:
>On 2017-09-28, Steve Wilson <no@spam.com> wrote:
>> "Tim Williams" <tmoranwms@gmail.com> wrote:
>>
>>> Correspondingly: iron bubbles in acid (HCl or H2SO4), nickel dissolves
>>> extremely slowly (H2O2 helps -- it's almost as noble as copper). Nickel
>>> forms an emerald green solution (in either acid).
>>
>>> Tim
>>
>> Good to know. Thanks. I don't like to deal with HCl, and I almost killed
>> myself with H2SO4. I will never deal with it again, and I used HCl only
>> rarely and under severely restricted conditions.
>
>As acids go, HCL is fairly tame, it's is the stuff in your stomach for instance.
>personally I have an irrational fear of electric shock after a few close
>calls.
HCL is also "Muriatic Acid", often used around pools, and in products
like CLR. I don't "fear" electric shocks but they do get my
attention. Try 100J through the chest from front to the back. Trust
me, it hurts.
On Sunday, October 1, 2017 at 11:31:20 AM UTC+11, Jasen Betts wrote:
> On 2017-09-28, Steve Wilson <no@spam.com> wrote:
> > "Tim Williams" <tmoranwms@gmail.com> wrote:
> >
> >> Correspondingly: iron bubbles in acid (HCl or H2SO4), nickel dissolves
> >> extremely slowly (H2O2 helps -- it's almost as noble as copper). Nickel
> >> forms an emerald green solution (in either acid).
> >
> >> Tim
> >
> > Good to know. Thanks. I don't like to deal with HCl, and I almost killed
> > myself with H2SO4. I will never deal with it again, and I used HCl only
> > rarely and under severely restricted conditions.
>
> As acids go, HCL is fairly tame, it's is the stuff in your stomach for
> instance.personally I have an irrational fear of electric shock after a few
> close calls.
It's not HCL but HCl - hydrogen (H) and chlorine Cl. There is no element with the symbol L - lithium is Li, lanthanum La, and lead Pb.
> "Tim Williams" <tmoranwms@gmail.com> wrote:
>
>> Correspondingly: iron bubbles in acid (HCl or H2SO4), nickel dissolves
>> extremely slowly (H2O2 helps -- it's almost as noble as copper). Nickel
>> forms an emerald green solution (in either acid).
>
>> Tim
>
> Good to know. Thanks. I don't like to deal with HCl, and I almost killed
> myself with H2SO4. I will never deal with it again, and I used HCl only
> rarely and under severely restricted conditions.
As acids go, HCL is fairly tame, it's is the stuff in your stomach for instance.
personally I have an irrational fear of electric shock after a few close
calls.
> The problem with the pure nickel strips from ebay is the nickel plating wore
> off quickly and the solution never turned green. I was left with the base
> steel which was useless for my application.
Reply by Tim Williams●September 30, 20172017-09-30
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:omutsc54285t4rt5g7cojq0ct5ipqml0be@4ax.com...
> Yes. Ground everything as often as possible, on a PC board or in a
> system.
>
> Use differential signals when you have to.
Differential is no panacea. LVDS has about the same noise rejection as 5V
CMOS.
One cannot escape their obligation to consider, and preserve, the voltage
between signal and ground, no matter how many signals or polarities one
uses!
(One of these days, I'm going to need a coax connector not firmly grounded,
and it's going to have better CMRR and EMI than anything else, despite how
terrible that sounds. Just takes a little logic.)
Although RS-422/485 receivers (and CAN, among others) do a good job of
helping you not need to worry about it.
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com
Reply by Steve Wilson●September 30, 20172017-09-30
John Larkin <jjlarkin@highlandtechnology.com> wrote:
> Yes. Ground everything as often as possible, on a PC board or in a
> system.
> Use differential signals when you have to.
Or use transformer coupling to break ground loops.
Reply by Phil Hobbs●September 30, 20172017-09-30
On 09/29/2017 02:28 PM, John Larkin wrote:
> On Fri, 15 Sep 2017 13:16:39 -0700, John Larkin
> <jjlarkin@highland_snip_technology.com> wrote:
>
>>
>>
>> Lots of people make parts like this:
>>
>> https://www.digikey.com/product-detail/en/bourns-inc/PWR5322WR250JE/PWR5322WR250JETR-ND/2022962
>>
>> The overload specs are almost always 5x rated power for 5 seconds, so
>> a 3 watt part can absorb 15 joules in that time. I wonder what happens
>> for shorter time overloads? Constant joules?
>>
>> Has anyone experimented with stressing this sort of small wirewound
>> resistor?
>>
>> I'll probably order some and blow them up. We'll be using low ohms,
>> 0.2 maybe, so we'll need a lot of current. There's a car repair place
>> and a motorcycle shop on our block, so maybe I could buy or borrow a
>> battery. For pure fast joules, I could just discharge some big
>> electrolytics.
>
>
> https://www.dropbox.com/s/oz62u59ourty079/Z420_C1.JPG?raw=1
>
> OK, I'm done. Here are some victims:
>
> https://www.dropbox.com/s/5it6rgc1wxcp8ah/Ex-Resistors.JPG?raw=1
>
Disappointing compared with your ex-fets picture. ;)
> I've got two parts that look reliable to pulse at 15 joules or so.
> Vishay AC05W looks best, didn't blow up until hours at 21 joules per
> shot.
>
> TE ER74 is a small 3 watt part, but very tough. Wouldn't die at 17
> joules over 30 hours, 0.1 Hz. But it swings a lot in body temperature,
> which is a worry long-term, so the 5 watt Vishay, with a lot more
> mass, is probably the safer choice.
Interesting, thanks.
Cheers
Phil Hobbs
>
> I think we can shut down at maybe 4 joules. I did test some big
> wirewounds that failed at 5J (like the big white rectangular one) in a
> couple of minutes of pulsing.
>
>
>
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net