** For SED readers.


Clockwise from top left,

1W carbon comp,

2W metal film,

0.5W metal glaze (cermet 150k),

0.5W carbon film,

centre = 0.5 watt metal film.



...... Phil

"Phil Allison" wrote in message ...

** For SED readers.

Clockwise from top left,

1W carbon comp,

2W metal film,

0.5W metal glaze (cermet 150k),

0.5W carbon film,

centre = 0.5 watt metal film.


COOL!!!!!!, miniature divining rods. ;-)

Bill Garber from GS-Electronics
http://www.garberstreet.com

"If you wish to forget anything on the
spot, make a note that this thing is to
be remembered." (Edgar Allen Poe)

On Sun, 16 Nov 2008 00:02:17 +1100, "Phil Allison"
wrote:


** For SED readers.


Clockwise from top left,

1W carbon comp,

2W metal film,

0.5W metal glaze (cermet 150k),

0.5W carbon film,

centre = 0.5 watt metal film.



..... Phil



The two in the center look like 1/4W (USA)to me.

However, I have seen Britished sourced parts where they have a series
that has 1W parts in the same package size as our 1/8W devices here.

We never believed it. Running 1W through a package that size brings
the node temps at the solder joints above reflow temps.

Similar to the claim the 2W parts in your pic make. Doesn't matter
what they can continuously dissipate and stay on value with. It matters
more that it is not so damned hot as to ignite combustibles proximal to
it.

Granted, a good designer never pushes such a part at its rated limit.

50% is a good idea for power resistors.

"Archimedes' Lever"
"Phil Allison"

** For SED readers.


Clockwise from top left,
1W carbon comp,
2W metal film,
0.5W metal glaze (cermet 150k),
0.5W carbon film,
centre = 0.5 watt metal film.


The two in the center look like 1/4W (USA)to me.


** Yes, the pair in the centre are 0.25 W metal film.

But the even smaller ones in the lower right are 0.5 watt Metal Glaze.


However, I have seen Britished sourced parts where they have a series
that has 1W parts in the same package size as our 1/8W devices here.

** The Metal Glaze types were made in Australia under licence from IRC -
the others are all of Asian origin except for the 1W carbon comps.

The power ratings are for an ambient of 70 C and a max surface temp of 155C
( excepting the carbon comps again.)


Similar to the claim the 2W parts in your pic make. Doesn't matter
what they can continuously dissipate and stay on value with. It matters
more that it is not so damned hot as to ignite combustibles proximal to
it.


** To get the full 2W rating, the resistor has to be mounted proud of the
PCB - either by use of a kink in the leads or ceramic stand-offs.

The trick with metal film and cermet types is they have low enough tempcos
(ie +/-100ppm) to stay within a 1% tolerance when very hot.


Granted, a good designer never pushes such a part at its rated limit.

50% is a good idea for power resistors.


** Unless you can fully submerge them in water

- then a 1000% up-rating becomes possible.



.... Phil

On Sun, 16 Nov 2008 00:02:17 +1100, "Phil Allison"
wrote:

:
:** For SED readers.
:
:
:Clockwise from top left,
:
:1W carbon comp,
:
:2W metal film,
:
:0.5W metal glaze (cermet 150k),
:
:0.5W carbon film,
:
:centre = 0.5 watt metal film.
:
:
:
:..... Phil
:


The resistors with the dull brown coating look like 1W metal oxide to me.

The 150K's look like the original 60-70's era Beyschlag metal films to me. The
end caps on these could become easily detached and the pattern was subsequently
changed to be similar to the centre resistors.

The commonly available "cheap" metal films such as those in the centre may have
a dubious 0.5W power rating but without the manufacturer specs you can't be
sure. Professional 1/4W sized metal film resistors (I am familiar with 80's era
Beyschlag and Roederstein - now all owned by Vishay) are rated at 0.6W @ 25C and
0.3W @ 70C if my memory serves me correctly.

"Ross Herbert"
"Phil Allison"
:
:** For SED readers.
:
:
:Clockwise from top left,
:
:1W carbon comp,
:
:2W metal film,
:
:0.5W metal glaze (cermet 150k),
:
:0.5W carbon film,
:
:centre = 0.5 watt metal film.
:

The resistors with the dull brown coating look like 1W metal oxide to me.


** I posted the ACTUAL types so folk would NOT make the dumb,

WRONG guesses like YOU just have.

Both Farnell and WES sell this kind of 2 watt MF resistor - look it up.


The 150K's look like the original 60-70's era Beyschlag metal films to me.


** I posted the ACTUAL types so folk would NOT make the dumb,

WRONG guesses like YOU just have.



The commonly available "cheap" metal films such as those in the centre may
have
a dubious 0.5W power rating but without the manufacturer specs you can't
be
sure.


** Read the WHOLE thread - the has been a correction on that one.



....... Phil

On Mon, 17 Nov 2008 12:37:50 +1100, "Phil Allison"
wrote:


"Archimedes' Lever"
"Phil Allison"

** For SED readers.


Clockwise from top left,
1W carbon comp,
2W metal film,
0.5W metal glaze (cermet 150k),
0.5W carbon film,
centre = 0.5 watt metal film.


The two in the center look like 1/4W (USA)to me.


** Yes, the pair in the centre are 0.25 W metal film.

I thought I had a memory issue. :-]

But the even smaller ones in the lower right are 0.5 watt Metal Glaze.


However, I have seen Britished sourced parts where they have a series
that has 1W parts in the same package size as our 1/8W devices here.

** The Metal Glaze types were made in Australia under licence from IRC -
the others are all of Asian origin except for the 1W carbon comps.

The power ratings are for an ambient of 70 C and a max surface temp of 155C
( excepting the carbon comps again.)


Similar to the claim the 2W parts in your pic make. Doesn't matter
what they can continuously dissipate and stay on value with. It matters
more that it is not so damned hot as to ignite combustibles proximal to
it.


** To get the full 2W rating, the resistor has to be mounted proud of the
PCB - either by use of a kink in the leads or ceramic stand-offs.

Yeah... then there are those types that are already packaged into a
metal "heat sink" type can with mounting feet on it. They need a block of
metal to dissipate into.

The trick with metal film and cermet types is they have low enough tempcos
(ie +/-100ppm) to stay within a 1% tolerance when very hot.

Yep. That makes them real good for many applications where a specific
load is needed, and needs to remain the same load you thought it was when
you put it on.

Granted, a good designer never pushes such a part at its rated limit.

50% is a good idea for power resistors.


** Unless you can fully submerge them in water


Of course. That is certainly going to be worlds better than air
dissipation. Water is actually VERY good at removing heat.

- then a 1000% up-rating becomes possible.

Yes... 3 orders of magnitude sounds about right. Works on computers
too, but not quite as good.

I like fluorinert (GE FC-40). One can immerse HV power supplies into
it, and have no fear of arcing. Something like 1200 Volt per mil
strength.

One of these days, I am going to make a deep freeze OC computer that
you'll see photos of in the magazines once I get it done. It will have
close to $600 worth of fluorinert running through it. It will be all
feng shui looking like a waterfall in some places. It is a shame that
goldfish cannot handle sub-zero temperatures.

Hey... I know! I'll get some perfluorocarbon fluid, heavily oxygenate
it, and keep a hamster in it for the photo shoot! On a running wheel!
Tied to a DC PM motor, tied to some LEDs!

I'll let it out for most of its life, feeding and breathing normally.
But I will have the world's best lil' "underwater" electric generator
hamster!

"Phil Allison" wrote in message
...

** For SED readers.


Clockwise from top left,

1W carbon comp,

2W metal film,

0.5W metal glaze (cermet 150k),

0.5W carbon film,

centre = 0.5 watt metal film.



..... Phil


Any results from the noise tests?

":-:Ghost Chip:-:"
"Phil Allison"

** For SED readers.

Clockwise from top left,

1W carbon comp,

2W metal film,

0.5W metal glaze (cermet 150k),

0.5W carbon film,

centre = 0.25 watt metal film.

Any results from the noise tests?


** Results were as follows:

1 watt carbon composition = 0.22 uV/V
0.5 watt *Metal Glaze (cermet) = 1.7uV/V ( !!!!!!!! )


0.25 watt MF = 0.09 uV/V

2 watt MF = 0.12 uV/V

0.5 watt carbon film = 0.22 uV/V


Testing was done over the audio band and noise voltage levels computed back
to " uV/V per decade of frequency " to be in line with maker's noise
specs.



....... Phil