Driver to drive?

[Spehro Pefhany]

On Mon, 03 Jan 2005 17:52:18 GMT, the renowned "WayneL"
<nospam-mail@wlawson.com> wrote:

Hi

I know industrial conductivity units use AC rather than DC, is there a
standard frequency?

No, both the voltage and frequency can vary over a wide range (as can
the conductivity of water from very contaminated to very cure). One
industrial- strength instrument for large scale dialysis installations
which I did instrumentation design for has both parameters
programmable. There's a bit of art to this stuff, and I suggest
finding a genuine expert in this kind of instrumentation, locally in
your own country, who is willing to help you pro bono.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[BFoelsch]

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2005.01.03.20.49.51.971318@example.net...

On Mon, 03 Jan 2005 09:56:03 -0500, Keith Williams wrote:

I've heard of ladder logic in traffic controls, but have never seen it.
I somehow don't think it would help with what I do, any more than
Greek. ;-)

As far as I understand it, it wouldn't be so much like learning Greek as
like learning Tinkertoys. ;-)

As I said, it's really just Visual Boolean. Vastly popular in the US PLC
market, not so popular in the European market. Like anything else, it has
its place. Like anything else, people who are comfortable with it tend to
use it even if other tools are more appropriate.

Cheers!
Rich

 

[Nick J.]

"n2mp" wrote:

Impedance spectroscopy segregates phenomenas according to their respective
time constants. Usually, charge transfer process is much faster than mass
transfer process, and the the former will appear on the impedance spectra
at
higher frequencies than the latter.
Warbug impedance is characteristic of the mass transfer-limited system. It
does not appear otherwise. This not means that the system is not a mix
between both electron and mass transfer but each phenomenas are
segregated...

That helps. I couldn't find "Warburg" listed in B&F's index (good book,
poor index) but its described in the section on EIS (chap. 10). Fig. 10.1.14
shows Rct (charge transfer R) in series with Zw (Warburg Z, defined as a
"resistance to mass transfer").

As for this conductivity meter, the electrochemical reaction
plays no role at all, so all the talk about Pt having a low
overvoltage etc means nothing.Pt is used because it does not
dissolve.

Let's say it MUST NOT play any role.
When you pass a current through an electrochemical cell, you always have
the following cell voltage decomposition :
Ecell = Ecell(I=0) + summ(R.I) + overvoltages.
The purpose of a conductivity cell is to determine summ(R). And, for that,
you must have : Ecell = summ(R) * Imeas.
Ecell(I=0) = Eqa - Eqc. When both electrodes are identitical, then Eqa =
Eqc.
Now, to have a significant measurement of your summ(R), you must have :
summ(R) >> overvoltages. And that's why Pt is used.

I can see how Pt would be especially good for EIS where very small amplitude
signals are used (e.g. the MacDonald EIS book suggests < 20mV, in order to
stay well below most redox potentials). For simple conductivity measurements
done with older, analog-based instruments, I've read that platinum black
helped avoid signal response attenuation due to polarization at higher
conductivities. Some digital instruments have other ways of dealing
with polarization effects (e.g. dynamically changing the drive freq to
better match the conductivity range).

The increase in surface area also has an effect to decrease the charge
transfer overvoltage, which is linked to the current density through
Butler-Volmer equation.

Any electrochemical reaction taking place at
the same time will have an impedance much higher than the
capacitive one, and not come into play. E.g. at about 1600 Hz and
a capacity of 100 uF, you have an impedance of 1 ohm, which
is much less than the solution resistance you are measuring. Any
electrochemical reaction taking place would for one thing have
a much larger impedance, and for another in any case, reduce that
figure even more because it is in parallel with the capacity.

I disagree...
First because the charge transfer resistance is a partly consequence of
the Helmoltz double layer capacitance build-up at the electrode/solution
interface.
Second because, when you make an EIS sepctra of an electrochemical system,
the first loop (at high frequencies) corresponds to the charge transfer
impedance : the capacitance corresponds to the Helmoltz double layer
capacitance and the loop's diameter correspond to the charge transfer
resistance.
To continue the comparison between EIS and conductivity cell measurement,
you can either work :
* at frequencies so high that the first capacitive loop is not yet formed.
That's why high frequencies AC current is used for the conductivity
measurement.
* with first capacitive loop as low as possible. That's why material with
very low charge transfer resistance, such as platinized platinum is used.
In commercial cells, both are used.

Of course if you've got EIS equipment then you've got the best conductivity
meter of all (paraphrasing from MacDonald et al) so you can check your
results. You should get the same bulk resistivity measurement at different
frequencies if you're properly compensating for all the other effects that
can cause inaccuracies in simple conductivity meter measurements.

That might be overkill for whatever Wayne had in mind. He might get good
enough accuracy by simply using an analog output on a DAQ box to drive a 500
mVp (low enough to avoid reducing any dissolved oxygen) square wave (say
3Khz) across the cell and use a 1-chip I/V transimpedance amp and high
sample rate analog input to integrate the signal's trailing 1/4 (thus
rejecting the initial charging of the cell capacitance) and do full-wave
rectification on it (to make any DC potentials cancel out) in software. Of
course this would have to be calibrated against two standard solutions of
different conductivities or by comparing to a commercial conductivity meter
(maybe he could borrow one just to do a calibration). If he wants to get
really fancy he could even make the software compensate for capacitive
"droop" as described in the Beckman patent (US 4808930).

Depending on whats in his solution, stainless steel or titanim electrodes
may give reasonable longevity between calibrations. Commercial probes often
use these materials. A concentric arrangement is preferable, e.g. two tubes
with the smaller one inside the bigger one so small relative movement
between them tends to cancel out as far as affecting the cell constant.

Nick J.

 

[Rich Grise]

On Mon, 03 Jan 2005 21:29:45 +0000, John Woodgate wrote:

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <u7djt05p1asc20us0d0hmqs771v8ao7j3o@4ax.com&gt
about 'Question for Win Hill/ Athlon64', on Mon, 3 Jan 2005:

I found it easier to implement a ladder-logic
processor than to write good programs for it.

I am striving to resist posting a series of 'ladder-logic' jokes. I have
to let one escape to relieve the pressure.

In Germany, all ladder-logic (Leiter-logik) is based on pairs of
semiconductors (Halbleiter).

I don't get it. Could you explain, or give more examples?

Thanks,
Rich

 

[Rich The Philosophizer]

On Sun, 02 Jan 2005 09:28:14 +0000, Kevin Aylward wrote:

Rich The Philosophizer wrote:
On Sat, 01 Jan 2005 08:37:27 +0000, Kevin Aylward wrote:

Rich The Philosophizer wrote:
On Thu, 30 Dec 2004 20:53:58 +0000, Kevin Aylward wrote:

Rich The Philosophizer wrote:
On Thu, 30 Dec 2004 09:22:18 +0000, Kevin Aylward wrote:

Sure, at the deepest level we have no free will.

I'm sorry, Kevin, but that is just plain not true, and no amount
of denial on your part can make it not true.

It is you that is in brainwashed denial. Sure, like you do today,
many years ago I also used to accept the free will was a valid
concept. I now know better.

How?

Do you mean why?

No, I mean how. As in, how do you "know better" (than that free will
is a valid concept)?

Oh... by logical deduction based on axioms.

No, that's not science.

Show me the study that you used. Show me the experiment that proves
conclusively that there is no such thing as free will.

Otherwise, you're no more credible than I am. This is only one of many
reasons I call you a dimwit.

Until you show me a reproducible experiment that can prove objectively
that there is no such thing as free will, I and the rest of the world will
know that you are nothing but a blowhard know-it-all-wannabe. And I will
continue to know that not only there is such a thing as Free Will, but
that it is the very foundation of life itself, and, ultimately, all of
Creation.

You will either ignore this post or cuss me out, or plonk me. I don't have
to be clairvoyant to predict the outcome of your Turing Tape, Kevin.
That's what happens when you deny your will.

Hm. Maybe you actually don't have any free will, because you're nothing
but a bot.

At least that's a f***ing logical conclusion, from your evasive
flimflammery.

Thanks,
Rich

Damn! I should have got the bong out last week! To heck with that one-hit! %-}
Of course, the latest batch of vodka assists with my articulation, as you
can see. %-Z

;^j
Rich again, pig-bladdering myself.

<fantasy>
[from audience]
Joe Schmoe: "Damn! That guy's a regular one-man show!"
Billy-Bob: "Yuh think he's really serious about that stuff?"
Jane: "Sounds like sex with this guy would be Kozmik!"
Proffesor Squat: "Hmmmmmmmm........"
</fan^H^H^H^H^H who am I trying to kid? <grammar police>Whom.</grammar
police>

 

[The Phantom]

On Wed, 05 Jan 2005 18:25:45 +0000, Guy Macon
<http://www.guymacon.com/> wrote:

The Phantom wrote:

Guy Macon <http://www.guymacon.com/> wrote:

If this doesn't frighten you enough, do a Google search
on [ oligotrophic ultrapure ].

One site (http://aem.asm.org/cgi/content/full/68/4/1548)
says "The extracellular polysaccharide matrix acts as a
diffusion barrier to nutrients and cellular products and
allows nutrients from the flowing water to reach bacterial
cells" ^^

Nutrients? What nutrients? It's just water with
"... less than 1ppb contaminants".

It doesn't seem like it, but they do grow in ultrapure water.
One kind makes a living by grabbing the manganese from any
stainless steel it finds.

But isn't it going to need something in addition to manganese (such
as carbon) to live? Where does it get the carbon? One of the sites I
looked at suggested they might get carbon from the dead carcasses of
other organisms present. But this can't go on forever can it? And
with so few of them present, what is the probability that a bacterium
that needs carbon is going to make contact with another (dead)
organism? This is all very strange.

Another grows (very slowly) these
fine white filaments that look like fine thread - I have seen
these growing in ultrapure water in a PTFE Teflon container.

Anything that can find nutrients there is going to be, as
they say, impossible to get rid of.

Not so. Bright UV lamps do the job. Then you have to
remove the tiny dead carcasses.

 

[legg]

On Fri, 31 Dec 2004 14:17:56 -0600, "Don A. Gilmore"
<eromlignod@kc.rr.com> wrote:

Hi guys:

I'm looking for a relatively thin electrically-resistive sheet material.
The resistivity I need depends on the thickness I can get. Basically I need
for the resistivity to be somwhere near

rho = .24 / t

where rho is the resistivity in ohm-m and t is the thickness of the sheet in
meters. I would like for it to be thin enough to be flexible in large
sheets (say, measured in square meters). Here are the corresponding
resistivities for some nominal inch thicknesses:

.031 in ---> 300 ohm-m
.062 in ---> 150 ohm-m
.125 in ---> 75 ohm-m
.188 in ---> 50 ohm-m

Are any of you aware of a material that meets these specs (or is close) that
is not extremely expensive? I have seen graphite-impregnated plastics that
could work well, but only in McMaster-Carr, which has a limited selection.
The material must be uniformly resistive throughout its cross section (not
just surface conductive).

Thanks for any replies.

You might try looking at some ferrite polymer material sheet stock,
though most mfrs are only interested in surface finish resistivity of
the treated material.

They are not designed for use as strictly resistive materials, so who
knows what they would do over a range of temperature or pressure.

Where defined, published resistivity shows a range between 500 and 21
ohm-meter, below 10KHz.

Siemens-Matsushita FPC C302, C350, C351.

http://www.epcos.com/inf/80/db/fer_01/05590563.pdf

http://www.epcos.com/inf/80/db/fer_01/05610563.pdf

http://www.epcos.com/inf/80/ap/e0001000.htm

Other mfrs MMG, Tokin, TDK, Hitachi, TSC and NEC.

RL

 

[gwhite]

jondoeengineer@hotmail.com wrote:

I know this question probably comes up a lot, as I've noticed from the
posts....

I want to build a very short range transmitter for operation in my
living room. Basically, I want to take the output of my subwoofer
channel from my home theater reciever and convert it to a digital
signal for broadcast to another part of the room. I'd like to be able
to hide the subwoofer and relocate it as needed without having to
reroute wires.

I think I can find enough info for the various circuits. However, I'm
pretty ignorant on FCC regs. I'm aware that the FCC requires that the
signal level be less than 250 microvolts at 13 meters from the antenna.
But, I have no idea how to test this. I understand this is typically
done in a lab, so of course, I wouldn't be able to test this. I also
understand that there is a formula for approximate conversion from the
transmitter power to signal strength:
(P*G)/(4*pi*D^2) = (E^2)/(120*pi)
P=Transmitter Power (Watts)
G=Antenna Gain
D=Distance (m)
E=Field Strength (V/m)

Ok, to make a long question even longer, I guess I'm asking if there's
an easy way to make sure I'm not violating FCC regs. I'd like to know
that by experimenting, I'm not going to get sued, fined or go to jail.
And also, I'd like to respect proper use of the spectrum.

I apologize for my ignorance. I'm a power engineer by education and am
trying to revive my long lost interest in elecronics. I can't imagine
a more useful thing to know.

Just don't do anything really stupid and you don't have to worry about
regulators if you are building a one-off "low" powered unit.

You don't even mention band.

 

[Max Hauser]

I'll try to follow up now on the relevant technical issues in this query.

Winfield Hill in <news:cqecnm0rs8@drn.newsguy.com>:
w: I'm sorry Max, I received neither of those emails you mention,
w: nor did I see the post you refer to. My long-standing home
w: email address has not been functional for about a year now,
w: and my work email should be used instead ... 10x more
w: spams than real mail ... 300 messages/day

I quite understand, I know the problem.


Winfield Hill in <news:cqeep7010so@drn.newsguy.com>:

Max Hauser wrote...

Both the first (1980) and second (1989) edition of the H-H
book contain a particular remarkable circuit design, for
example Figure 9.73 of the first-edition copy that I've seen
(9.90 in the second). This design is a pseudorandom noise
generator with programmable spectrum, demonstrating
several important electronics principles at once. What I
found most striking about it was how closely it resembles
the circuit published, if I recall, the year before the first
edition, in _Electronic Design_ magazine by Michael
Workman of IBM. ... This unusual design appears
unattributed in both editions of the Horowitz-Hill book that
I have seen. I _don't_ know or presume the exact history ...

w: I remember working with Paul on that drawing, which would
w: have to have been sometime in 1977 or 1978. The inspiration
w: for our design was an HP instrument which came out probably
w: in the early 70s. This instrument fully laid out the technique,
w: although it was more complex than our design, and I thought
w: we could devise a more simple version. I don't recall the
w: Workman article in ED, although I may have seen it - could
w: you send me a copy? It would be interesting to compare
w: and consider the differences.

I certainly plan to do that once I get it back into my possession. I do not
have the article at hand now, though I have some other relevant literature
I'll mention below.

But at this point I should explain something that (from other replies) may
have been unclear to some people who have not seen the circuits in question.
The two circuits are interesting not because they are LFSRs (linear-feedback
shift registers). Rather, they start with LFSRs built specifically from
long CMOS shift registers, then they exploit the time-shifted output
sequence inherent in shift registers with parallel outputs, and the
rail-to-rail voltage swings of CMOS logic, through an array of
analog-weighted resistors, forming a compact analog FIR filtering function
with inherent D/A conversion, the resistor conductances defining the filter
impulse response (IR). The Fourier transform of this IR then weights the
natural spectrum of the LFSR digital pseudonoise generator, so that you get
an analog pseudonoise output, with _arbitrarily_ programmable spectrum. The
circuits are remarkable both for the concert of principles, in my opinion
(analog and digital, continuous- and discrete-time), and also for the
coincidence of practical details in these two published versions.
(Workman's _ED_ article included a programmable-calculator algorithm to set
the resistor weights for a desired output spectrum.)

Along with CMOS implementation specifics, these circuits depart from the
famous Hewlett-Packard 3722A pseudonoise generator, by exploiting
time-lagged shift-register outputs for analog FIR filtering. (I have 3722A
details in the 1970 H-P catalog.) Another analog pseudonoise generator
design, published in _Electronics_ circa 1980 by Henrique Sarmento Malvar at
the University of Brasilia, uses a CMOS LFSR, but applies continuous-time
lowpass filtering to a _one-bit_ binary output.

For those of you interested in general, yes, LFSRs are a type of recursive
digital filter or limit-cycle oscillator defined on Galois fields. The
formalism is exact. Take a series of clocked delay cells carrying modulo-N
integer numbers, tap off some linear combination using the modulo-N
arithmetic, and feed it back to the input. Then you will get pseudorandom
cycles as the clock runs, details dependent on tap arithmetic and on initial
values (state) in the delay cells. (Basics of LFSR were not however the
focus of my query.)

w: If you examine our book, you'll see that we have very few
w: references. ... it was clear we could not take the time to find
w: good or accurate references for everything we were presenting,
w: and therefore we didn't even try.

Again the similarity to a published circuit triggered the query. I don't
know which came first, but I favor acknowledgement. (Some authors are very
casual indeed about these things, in more recent years.)


"Michael Black" in <news:cqeoe8$fnb$1@theodyn.ncf.ca>
m: We're talking about a shift register set up for a pseudo-
m: random output? The concept was out there before this. ...
m: Don Lancaster also wrote about it. I can remember an
m: article in Radio Electronics in mid-1975. And he covers it
m: in his TTL Cookbook with 1974 copyright. Even better, he
m: used the concept in his Psych-Tone in the February 1971
m: issue of Popular Electronics, page 25, to generate random
m: musical tones.

Above I explained further details common to the two circuits. But what a
small world! Some of us can trace engineering careers, in part, to Don
Lancaster's 1968 Decade Counter Unit (DCU) in Pop'tronics in 1968, with
sequels. In 1973 I wrote to Don Lancaster to show a pseudorandom beep-tone
generator of my own, built at the time for a parrot that was hard to please.
(Dubbed a Pseudorandom Parrot Pleaser.) Later (1974) built into a nice
hand-held box (LMB Crown Royal series) and renamed a Cyclodigitron, in honor
of a famous fictional computer advertised in the 1960s on then-MIT campus
radio station WTBS, called a Dynadigitron. (Mine used a CD4006 18-bit shift
register with a second chip, CD4011 quad NAND, as XOR for feedback.) Memory
lane.


"Harry Dellamano" in <news:efCyd.4936$2X6.525@trnddc07>:
h: I remember working at Beckman Systems Division in 1967
h: and using a 22 bit pseudo random noise generator ...
h: implemented with Sylvania SOUL-!! 5V TTL devices.

"Nicholas O. Lindan" in
<news:7aFyd.11470$Z47.4961@newsread2.news.atl.earthlink.net>:
n: > Sylvania SOUL-!!
n: SUHL: Sylvania's Universal High-Level Logic
n: Premiered 1963. Was used for the control computer, a
n: Bailey 855, at Three-Mile Island....still in production in 1979.


Good stuff, SUHL I and II. If you missed the "old-fart electronics quiz"
that I posted here 2 Aug 87 (sci.electronics) and 17 Jan 04, Question 11
asked about SUHL (and also SN7300 series, CCSL, HTL, ECCSL, Utilogic, and
COSMOS).


"Don Lancaster" in <news:41D057FC.1339FC68@tinaja.com>:

d: The PsycTone came about at Goodyear Aerospace when a
d: cubical mate was applying these sequences to a multi-million
d: dollar aerospace project and I told him I thought I could make
d: them squawk.
d: See http://www.tinaja.com/glib/atg1.pdf


A happy 2005 to all -- Max

(The limerick wasn't bad, either, IMO.)

 

[Fritz Schlunder]

"Peter Kiproff" <peter@microtrendrobotics.ca> wrote in message
news:gJqCd.11439$P%3.1022645@news20.bellglobal.com...

I have a problem " In another city " with some electronic controls on a
brake press.
The brake's ram is hydraulic with 3 electric valves & micro switches to
control the positions for
Top of stroke, Pinch point where the ram slows, & Bottom usually a 90 deg
die for sheet metal fabrication.

Most basic controls for this function are 115VAC, This one is 110VDC, When
the valve is turned off there is some kind of high voltage discharge,
adversely affecting other logic.

The only other info I can supply is that it is fused for 5 amps total & 2
of
the valves can be on @ the same time, so I suspect approx 1Amp+ for each
valve. Also I've noticed if a relay is used in place of the micro switch a
spark can be seen!

What would be your best guess for a RC snubber to keep this from affecting
the logic?

I remember reading a .1uf & 47 ohm in series across the coil would work,
so
in a pinch I paralleled two 100 ohm 1/4W resisters & used a .1 uf @ 600v
cap. but without being able to measure I don't know if that is enough.

I'd rather over kill somewhat to make sure, the cycle rate would be every
few seconds @ most.

What would be your recommendation?

Thank you
Peter

If this valve is juiced up by DC, then all you should need is a diode
antiparallel to the valve coil. Something like a 1N4004 should be fine.
Adding this diode will add a little bit of turn off delay, but it doesn't
sound like that would be much of a problem.

 

[Clarence_A]

"John Larkin" wrote

Jim Thompson wrote:

<snip>

What IS "ladder-logic"?
...Jim Thompson

It's a graphical way to program PLC's, industrial programmable
logic
controllers. A screen has two horizontal "voltage rails" at the
top
and bottom, representing some voltage bus and ground. The user
then
draws vertical rungs from rail to rail, consisting of some
string of
series or parallel contact closures (representing logic states,
like
maybe a pushbutton or a pressure switch) and circles
representing
actuators or relay coils. Relay contacts can be named and used
on
other rungs, sort of a logic fanout.

You can have nc or no contacts, time-delay relays, all sorts of
stuff.
It's easy to make rs flipflops, gates, and like that. There are
even
kluges for analog i/o and bus data operations and other
weirdness.
I've even seen a Basic program inside a box: when power is
applied,
the code runs!

This was invented in the olden days to simulate hardwired relay
logic
that factory dudes were used to. They advertised "no programming
necessary!" One PLC would then replace a panel full of relays.

Here's one, except that the rails are vertical...
http://xtronics.com/toshiba/Ladder_logic.htm
John

I have never seen any "Ladder Logic" where the rails were other
than vertical.

It is an extension of relay logic, which permits software to be
inserted into the flow as if the routing was a relay. I used to
program a complete system in ladder Logic right in the body of a
quote because it allowed the customer to verify with their
electrician that it was what they wanted. Basically it is Boolean
Logic for AC or DC relays!

 

[Terry Given]

Zak wrote:

Rolavine wrote:

Good points. How is a 1N4004 as a flyback eater diode? Is it fast
enough? When
I look up the specs they are not very specific about speed, since they
are
intended to be rectifiers, however when I test them they seem fast
enough, my
100 meg scope shows no transient.


I think 'fast' with diodes applies to the opposite direction: how fast
they go from conducting to no current again. How much this bites you
depends on switching speed to the on state (off state for the diode) and
the frequency.


Thomas

Correct - this is called reverse recovery. Diodes also have the
equivalent forward recovery time, usually unspecified. a 1n400x has a
reverse-recovery time of tens of microseconds. That just means dont use
them in switchmode power supplies

Cheers
Terry

 

[John Woodgate]

I read in sci.electronics.design that jimp@specsol-spam-sux.com wrote
(in <crek8h$68q$1@mail.specsol.com&gt about '40M for Bush Inauguration
and 15M for Tsunami Disaster WAS Re: Bush accused of undermining the UN
with aid coalition', on Tue, 4 Jan 2005:

Speaking of heavy lifters, there was a blurb on the news this morning to
the effect that in some areas the only usable machinery is elephants.

It's not 'usable' but 'available'.

Seems they don't need runways or roads, can haul a lot of stuff, and are
really good at clearing debris.

They are pretty good at large-scale mechanical handling, but they are
hopeless at SMD assembly.

Not to mention they work for peanuts...

Lots and lots of peanuts! Actually, a lot of their food supply has
probably been destroyed.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Matthew Russotto]

In article <z8BZpXMIwt2BFwbh@jmwa.demon.co.uk>,
John Woodgate <noone@yuk.yuk> wrote:

I read in sci.electronics.design that jimp@specsol-spam-sux.com wrote
(in <crek8h$68q$1@mail.specsol.com&gt about '40M for Bush Inauguration
and 15M for Tsunami Disaster WAS Re: Bush accused of undermining the UN
with aid coalition', on Tue, 4 Jan 2005:

Speaking of heavy lifters, there was a blurb on the news this morning to
the effect that in some areas the only usable machinery is elephants.

It's not 'usable' but 'available'.

Seems they don't need runways or roads, can haul a lot of stuff, and are
really good at clearing debris.

They are pretty good at large-scale mechanical handling, but they are
hopeless at SMD assembly.

There's an NIH-IBM pilot program trying to breed microscale and nanoscale
varieties to handle that and similar problems.

 

[John Larkin]

On Tue, 4 Jan 2005 18:56:23 +0000, John Woodgate
<jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that John Larkin <jjlarkin@highSNIPland
THIStechPLEASEnology.com> wrote (in <efolt05b12bhoot3t1bvlmq84mk258d009@
4ax.com&gt about 'OT: Safe Riddles', on Tue, 4 Jan 2005:
On Tue, 4 Jan 2005 08:27:51 +0000, John Woodgate
jmw@jmwa.demon.contraspam.yuk> wrote:

I read in sci.electronics.design that Clifford Heath <no@spam.please
wrote (in <33un4sF43pcd2U1@individual.net&gt about 'OT: Safe Riddles', on
Tue, 4 Jan 2005:
White noise is completely unpredictable, and
so is completely uninteresting.

Not if you are in a steam-driven plant!


On the ships I used to work on, if the engine crew suspected a
high-pressure steam leak - you could usually hear it but not see it -
they'd get a broomstick and carefully wave it around all the welded
pipe joints. If the steam jet sliced off the end of the stick, well,
there it was.

That's about it. Used to be a story told by the guides at Chatham
dockyard. Probably still is. I've seen a film of a demo. Scary! You
can't see a thing, just this very high-pitched noise. And the end of the
stick is sliced clean off.

I was on one ship when they tested the safeties for the Coast Guard
inspection. Just turn up the flames and wait for it to blow. There was
this guy who stood next to the valve, above the boiler, and tweaked it
if necessary. That's all this guy did for a living, adjust safety
valves. He wasn't pretty, having been cooked a few times himself.
Steam scares me.

John

 

[Guy Macon]

The Phantom wrote:

(Concening things that grow in ultrapure water that has nothing but
pureH20 down to the perts per billion level)

But isn't it going to need something in addition to manganese (such
as carbon) to live? Where does it get the carbon? One of the sites I
looked at suggested they might get carbon from the dead carcasses of
other organisms present. But this can't go on forever can it? And
with so few of them present, what is the probability that a bacterium
that needs carbon is going to make contact with another (dead)
organism? This is all very strange.

It is indeed. When it comes to biology I am a pretty good electrical
engineer, but I have seen with my own eyes the slime that lives on
stainless steel in ultrapure waterand I have seen the slow-growing
filaments that can grow in ultrapure water in a polypropylene container.
Life manages to find a way.

--
Guy Macon <http://www.guymacon.com/>

 

[John Larkin]

On 4 Jan 2005 13:57:05 -0800, "Pat" <patrick.nee@lmco.com> wrote:

Hello everyone.

I'm working on an ultrasonic detection system. We're driving a
Piezo element on the end of a long coax cable, and we're driving it
with a voltage spike anywhere from 100V to 500V, with a rise time
around 15ns. The return signal is an ultrasonic pulse around 5MHz, and
relatively weak (0.5mV).

I'm currently working on the receiver circuit, which listens to the
same co-ax, next to the driver circuit. I'd like a way of passively
surviving the spike.

I initially ran 5K in series with the input, and shunted that to gnd
with 1N4148s (see below). The problem is the capacitance of the diodes
draws too much current through the resistor and kills the signal. I
could reduce the resistors, but then that starts to divert more power
from the Piezo. I guess I could look for lower capacitance diodes, or
run two in series, but it seems like there's probably a better way.

Anyone have any ideas?


.Piezo 5K
.Input>------/\/\/\/-----*------>LNA
. |
. |
. ---
. \ / 1N4148
. ---
. |
. |
. |
. -----
. ---
. -

I'd suggest a small series cap, a few pF maybe, a gated active clamp
(a gaasfet would be ideal, or maybe a schottky diode pair) and then a
fet amp. 5 pF is about 6K at this frequency. The clamp could run in
the couple ohms range when on and maybe a couple pF when off.

Hmmm, maybe something could be done with a tuned circuit and a clamp.
That would give better signal transmission into the fet, and the
active clamp would kill the Q and shunt the signal to ground.


-----C--------+-------------+-------- amp
| |
L d
| g------ control
gnd s
|
gnd


something like that?

John

 

PMC-SIERRA STOCK FOR SALE ,FREE DATASHEETS ALSO AT: WWW.SIERRAIC.COM
Partnumber Mfg price Link to order
PM8313-RI PMC-SIERRA $53
https://www.sierraic.com/pnresults.asp?part=PM8313RI
PM7324-BI PMC-SIERRA $210
https://www.sierraic.com/pnresults.asp?part=PM7324BI
PM5357-BI PMC-SIERRA $125
https://www.sierraic.com/pnresults.asp?part=PM5357BI
PM5347-RI PMC-SIERRA $89
https://www.sierraic.com/pnresults.asp?part=PM5347RI
PM3390-BC PMC-SIERRA $50
https://www.sierraic.com/pnresults.asp?part=PM3390BC
PM8316-PI PMC-SIERRA $300
https://www.sierraic.com/pnresults.asp?part=PM8316PI
PM5342-BI PMC-SIERRA $89
https://www.sierraic.com/pnresults.asp?part=PM5342BI
PM4388-RI PMC-SIERRA $44
https://www.sierraic.com/pnresults.asp?part=PM4388RI
PM5313-BI PMC-SIERRA $199
https://www.sierraic.com/pnresults.asp?part=PM5313BI
PM5363-BI-AP PMC-SIERRA $175
https://www.sierraic.com/pnresults.asp?part=PM5363BIAP
PM5365-PI-CP PMC-SIERRA $129
https://www.sierraic.com/pnresults.asp?part=PM5365PICP
PM5312-SI PMC-SIERRA $99
https://www.sierraic.com/pnresults.asp?part=PM5312SI
PM73487-PI PMC-SIERRA $150
https://www.sierraic.com/pnresults.asp?part=PM73487PI
PM7390-BIAP PMC-SIERRA $220
https://www.sierraic.com/pnresults.asp?part=PM7390BIAP
PM8355-PC-CP PMC-SIERRA $35
https://www.sierraic.com/pnresults.asp?part=PM8355PCCP
PM5355-SI PMC-SIERRA $75
https://www.sierraic.com/pnresults.asp?part=PM5355SI
PM8315-PI-EP PMC-SIERRA $109
https://www.sierraic.com/pnresults.asp?part=PM8315PIEP
PM5344-RI PMC-SIERRA $40
https://www.sierraic.com/pnresults.asp?part=PM5344RI
PM7321-QI PMC-SIERRA $55
https://www.sierraic.com/pnresults.asp?part=PM5344RI
PM4341A-RI PMC-SIERRA $10
https://www.sierraic.com/pnresults.asp?part=PM4341ARI
PM7345-QI PMC-SIERRA $70
https://www.sierraic.com/pnresults.asp?part=PM7345QI
PM4341A-QI PMC-SIERRA $15
https://www.sierraic.com/pnresults.asp?part=PM4341AQI
PM7364-BI PMC-SIERRA $125
https://www.sierraic.com/pnresults.asp?part=PM7364BI
PM73121-RI PMC-SIERRA $75
https://www.sierraic.com/pnresults.asp?part=PM73121RI
PM7384-BI PMC-SIERRA $325
https://www.sierraic.com/pnresults.asp?part=PM7384BI
PM73488-PI PMC-SIERRA $199
https://www.sierraic.com/pnresults.asp?part=PM73488PI
PM7366-BI PMC-SIERRA $60
https://www.sierraic.com/pnresults.asp?part=PM7366BI
PM4344-RI PMC-SIERRA $28
https://www.sierraic.com/pnresults.asp?part=PM4344RI
PM4388-NI PMC-SIERRA $44
https://www.sierraic.com/pnresults.asp?part=PM4388NI
PM7345-RI PMC-SIERRA $32
https://www.sierraic.com/pnresults.asp?part=PM7345RI

Sierra IC Inc. Strives to be the strongest link in your supply chain !


Solving all of your sourcing problems for OEM's, Contract
Manufacturers and Distributors With Staff with over 15 years experience
in the electronics industry, and Stock from all major manufacturers.
Sierra IC Inc is your Online Store for Purchasing Hard to Find,
Obsolete and Allocated Electronic Components.

 

[Dieter Britz]

Guy Macon wrote:

John Larkin wrote:

Guy Macon <http://www.guymacon.com/> wrote:


Also what is the best way of storing ultra pure water

It doesn't exist. You need to purify it on the spot. Ultrapure
water will dissolve anything it possibly can, and you want to give
it as little time leaching chloride from plastics and dissolving
metals and glass as possible. Making pure water is difficult,
and keeping it that way is impossible

Ice?


John, that's the most brilliant yet simple idea I have heard in
quite some time. Freeze the ultrapure water, and before you thaw
it saw away or melt away the outer layer. That sounds like it
would work.

I imagine the block of ice will be very, very clear.

This is the standard answer to the question, how do you contain
the universal solvent? In a container of the frozen solvent itself.

Sawing slices off the ice would again contaminate the water,
unless you use a Pt saw. I believe Wayne has limited means...

Wayne: I doubt that you can buy this pure water; you probably need
to get hold of a quarz triple stil, or permission ot tap from one.
Use quarz bottles (expensive) or teflon, as someone suggested. It
has also been mentioned that you quickly contaminate the water again,
initially with O2, CO2 etc from the air, then from the container walls
or residues on them.

Bockris and coworkers did some fine work in the '50's on solid
electrodes. Until then, people were saying that you can't do
useful work on them because of contamination, Hg was king, in
the form of the dropping mercury electrode, clean every time a new
drop comes out. They used the trick of distilling water and other
stuff (like HCl/water) directly into their cell. That way they got
around the storage problem. I don't know whether you can do that.

Deionised water might be free of ions, but it might also have
organic impurities. In our lab, we START with deionised water,
feeding it into our quarz stil. A key word (google!) is "pyrogens".

--
Dieter Britz, Kemisk Institut, Aarhus Universitet, Danmark.

 

[n2mp]

Hello,

"WayneL" <nospam-mail@wlawson.com> a écrit dans le message de news:
zJBCd.323$II4.29@newsfe5-win.ntli.net...

I understand the overvoltage principle and know that it applies to
biased ac (10-20mV).
But if you had NO bias and just applied AC peak to peak say volt what
would the outcome be?
If the p-p voltage was lower than the cell "overpotential" (not
overvoltage) then there would be know effect apart from the oscillations
of ions species?

I don't understand your questions...
For me, an humble electrochemist, there is no difference at all between
overvoltage and overpotential...
What's true for DC is also for AC. The only difference is that, if the AC
signal's frequency is too high for the system to react, then the slow
phenomenas won't appear. And that's why EIS is a powerful analytical
technique : as AC signal's frequency progressively decreases, the slowlier
phenomenas appear and impedance changes.
In addition, 1V seems a too high AC signal to me to be sure that the E=f(I)
evolution remains linear. However, this depends on the impedance of your
system. For some milliohm impedance systems (ex: batteries), it will surely
be too high. For very low conductivity systems (ex : very diluted
solutions), it might not be enough...

Best regards.

--
Enlevez ".nospam" de mon adresse e-mail pour me répondre.
--------------------------------------------------------------------------------------------------------
Remove ".nospam" from my email address to reply me.