MessageView 421F schematic

[John Fields]

On Mon, 01 Mar 2004 07:53:45 GMT, Robert Baer <robertbaer@earthlink.net>
wrote:

Most of the better analog VOMs are rated at 20,000 ohms/volt (ie: 50uA
at full scale).
Most of the DMMs are rated at 10Megohms.
Since a DMM samples and there is a long time between samples, they
usually miss a "slow spike" more often than not.
But a VOM needle will "jump" or otherwise fluctuate.
However, if the "spike" is a relatively fast and "low level", both
meters will miss it.
Fast, regular pulses will show on a VOM as a DC level which is the
average value, and if one knows the rep-rate, one could calculate the
approximate peak level and pulse width.
So, in special cases, they can compliment each other.

VOM: "Hi there, you're looking particularly good today!"

DMM: "Thanks, so are you!"


--
John Fields

 

Hello all,

Thank you for all of the replies. I appreciate it.

In this case I was reacting to some recent readings which indicated
that it would be a good idea to have an analog VOM to see spikes that
a DMM would miss. After some looking into the issue I was simply
coming away with being unsure of the necessary sensitivity that a VOM
would have to be.

Perhaps this opens into a broader issue that I have been concerned
about, namely trying to learn practical electronics from books. While
I would love to take courses in Electronics Engineering Technology
time has just not allowed me to do so. I am hopeful this will change
in the near future, but until then I will have to rely on books and
hope that I did my research correctly and therefore am learning
correct information.

Since I already have a DMM it would seem, if I understand correctly,
that the VOM would make a good educational compliment to the DMM but
would not really be useful for everyday troubleshooting. And, when my
prowess grows in electronics, that I will be best served by the DMM
and an oscilloscope. Is this correct?

So much to learn!!! Hopefully it will be an interesting and
enjoyable journey.

Thanks again, all!

Always,

Sam



On 1 Mar 2004 06:31:53 GMT, "Walter Harley"
<walterh@cafewalterNOSPAM.com> wrote:

jacobson98@earthlink.net> wrote in message
news:v52540l890qjj9ln951kfih04g5m5mho0d@4ax.com...
If I understand correctly, then, the 20K VOM would be just fine as a
analog meter for most applications, and that if I want precise
measurements for "spiking" the best choice would be an oscilloscope.
Thus the tandem of a 20K VOM and an oscilloscope would be fine.
However for general multimeter usage, since the oscilloscope will
catch the "spikes" better, the proper choice would be a DMM. Is this
correct?

A pretty good rule of thumb is "do what everyone else does unless you know
better." These days, people use digital DMM's for most purposes, and analog
multimeters are relatively uncommon.

(I know a bunch of the oldtimers on this group are about to say "hey, I use
one every day"; to which, let me just say that I used an ancient HP vacuum
tube AC voltmeter just a couple of days ago. And I sometimes fantasize
about buying a Simpson 260 for my audio work. But a quick look at the
catalogs will tell you which ones are more common nowadays.)

A quality DMM is much cheaper and easier to find than a quality analog
meter, these days. For that matter, a cheap DMM is cheaper than a cheap
analog meter, and probably better able to take being tossed around in a
toolbox.

An oscilloscope is a whole different beast. You talk about wanting to
measure "spikes"; there are a lot of things you might mean by that. Analog
meters do tend to have faster response than digital meters, but they're
still not fast enough to see the sort of spikes that digital circuitry can
cause. For that you would indeed need an oscilloscope; but before you go
out and get one, you might want to do a bit of research into what a scope
does and how to use it. There were several threads on this NG recently
instigated by a fellow who went out and bought a used scope without a clue
of how to use it, and couldn't even figure out whether or not it was
working. A scope is NOT a "turn it on and connect the test leads" device,
like DMM's often are.

 

[Watson A.Name \"Watt Sun]

jacobson98@earthlink.net wrote:

Hello all,

As I am a newbie in the world of theoretical and practical
electronics I have come across quite a few ares that I have questions
in. One subject that I am not clear on is the level needed for
accurate measurements via an analog voltmeter and/or a multimeter.

I understand that, as per the mathematics, the higher the impedence
value the more accurate the measurement from the meter. However I was
wondering what would be the necessary level of ohms/volt that an
analog voltmeter and/or a multimeter would need to operate at in order
for the measurement(s) being displayed to be considered accurate for
the testing of compuers/arcade PCB's, as well as general trouble
shooting of other common electrical devices (phone, PDA, etc.). Is
20,000 ohms/volt generally satisfactory, or does one really need a
50,000 ohms/volt meter?

As a note, I have a digital multimeter that is rated at 4 megaohms,
however, I am interested in the analog multimeter so that I can see
any spikes that may be produced by the electrical device.

If you want to look at spikes, you need an oscilloscope, _not_ an analog
multimeter. Use your meter for what it's intended, and use the 'scope
for what _it_ is intended.

Thank you all for your time and advice!

Respectfully,

Sam

 

[Jim Yanik]

jacobson98@earthlink.net wrote in
news:8a4640pcfbahp3jjq8tabl956kilqtu2un@4ax.com:

Hello all,

Thank you for all of the replies. I appreciate it.

In this case I was reacting to some recent readings which indicated
that it would be a good idea to have an analog VOM to see spikes that
a DMM would miss. After some looking into the issue I was simply
coming away with being unsure of the necessary sensitivity that a VOM
would have to be.

Perhaps this opens into a broader issue that I have been concerned
about, namely trying to learn practical electronics from books. While
I would love to take courses in Electronics Engineering Technology
time has just not allowed me to do so. I am hopeful this will change
in the near future, but until then I will have to rely on books and
hope that I did my research correctly and therefore am learning
correct information.

Since I already have a DMM it would seem, if I understand correctly,
that the VOM would make a good educational compliment to the DMM but
would not really be useful for everyday troubleshooting. And, when my
prowess grows in electronics, that I will be best served by the DMM
and an oscilloscope. Is this correct?

Yes.

--
Jim Yanik
jyanik-at-kua.net

 

[normanstrong]

<jacobson98@earthlink.net> wrote in message
news:nqo440le8q47nturkvfah9shttc0tclqii@4ax.com...

Hello all,

As I am a newbie in the world of theoretical and practical
electronics I have come across quite a few ares that I have
questions
in. One subject that I am not clear on is the level needed for
accurate measurements via an analog voltmeter and/or a multimeter.

I understand that, as per the mathematics, the higher the
impedence
value the more accurate the measurement from the meter. However I
was
wondering what would be the necessary level of ohms/volt that an
analog voltmeter and/or a multimeter would need to operate at in
order
for the measurement(s) being displayed to be considered accurate for
the testing of compuers/arcade PCB's, as well as general trouble
shooting of other common electrical devices (phone, PDA, etc.). Is
20,000 ohms/volt generally satisfactory, or does one really need a
50,000 ohms/volt meter?

As a note, I have a digital multimeter that is rated at 4
megaohms,
however, I am interested in the analog multimeter so that I can see
any spikes that may be produced by the electrical device.

Most digital multimeters have an input impedance of 10 megohms. For
your application, I would recommend a DMM having a high speed bar
graph in addition to the digital readout. These bargraph displays are
about 10 times the speed of the digital portion and will almost always
reveal the presence of transients.

If the spikes are very short you'll have to break down and get an
oscilloscope.

Norm Strong

 

[JeffM]

So, in special cases, they can compliment each other.
Robert Baer

VOM: "Hi there, you're looking particularly good today!"
DMM: "Thanks, so are you!"
John Fields

http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=complement&x=0&y=0

 

[Walter Harley]

"Will" <willdangerrobinson@blueyonder.co.uk> wrote in message
news:2A01c.5553$bQ2.3820@news-binary.blueyonder.co.uk...

I have aquired these items and would love to know what they are!
Help is gratefully accepted and appreciated.
Thanks in advance.........Al

Please don't post binaries to sci.electronics.design. Many usenet providers
won't even preserve the attachment, in a non-binaries group.

Alt.binaries.schematics.electronics (a.b.s.e) is a good place. But even
there, a 1MB posting is a bit excessive. Change your compression settings,
or rescale your images.

Thanks.

 

[Walter Harley]

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:c22h45$2tu$0@216.39.172.65...

Alt.binaries.schematics.electronics (a.b.s.e) is a good place.

sorry, that's alt.binaries.schematics.electronic (no 's' at the end).

 

[tk]

Walter Harley wrote:

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:c22h45$2tu$0@216.39.172.65...

Alt.binaries.schematics.electronics (a.b.s.e) is a good place.


sorry, that's alt.binaries.schematics.electronic (no 's' at the end).


My stupid giganews server doesn't seem to have that one...

 

[Walter Harley]

"tk" <tk@tk.com> wrote in message news:i-ydnZUudLGNGtjdRVn-jA@comcast.com...

sorry, that's alt.binaries.schematics.electronic (no 's' at the end).


My stupid giganews server doesn't seem to have that one...

Yeah, that's the problem with binary newsgroups, not all providers carry
them. Out of interest, did Giganews give you the attachment on the original
posting?

The best thing to do with big attachments is probably to post them to one's
own web page, and then just include a link. That way anyone can see the
item, regardless of who their provider is. If the OP had done that, he
might have some useful responses by now...

 

[Ken Weitzel]

SIOL wrote:

Ken Weitzel wrote:


Hi...

I'm an old guy, long retired and stroke damaged, but
maybe I can help to bring a little peace... hey, I'm
a Canadian, that's what we do

Jan, it doesn't detect x-rays. No detectors there, none
at all, never were.

What's happened is that the various and sundry experts
have decided among themselves at what level of HV the
set will emit greater than acceptable radiation...

So, the HV is capped at (or slightly below) that
point. If it rises above the set shuts down.

Hope that helps. Now be nice to each other, and
helpful

Take care.

Ken


Sounds reasonable. I've had a milion different monitors dissassembled on my
bench and have NEVER seen actual X-ray detector inside.
Not even in service manuals.

It's usually a bit that shuts down the monitor when primary peak HV
transforme current exceeds some level and that is more or less all.

Regarding being bit by a supposedly empty CRT capacitance, IIRC this is a
long known effect and its being caused by charge bleeding by dielectric- in
this case the glass.

Older techs have known about this when woking with large, high voltage oil
capacitors, whiche were notoriously known for this, ableight it canppen
even wth elkos sometimes to a visible degree.
When charged, charge gets slowly into upper layer of dielectric through
small parasitic current, ion migration etc.

When discarged, trapped charge inside boundary layers of dielectric slowly
trickles back to plates and causes voltage regeneration...

Hi...

YES! I'm one of those old guys...

Perhaps boring to the younger fellows; but in the
old days if a crt was "gone" but had an unbroken
neck for an inch or so behind the bell, we'd have
them re-built. This meant a special trip to the
re-builder, so we'd save up a bunch before taking
them in.

I can guarantee you that they were well shorted
before being set aside. But if it sat for even
weeks and you foolishly picked it up so your
arm was near the 2nd anode, and you were holding
the dag as well, it was very unpleasant!

Just touching on the original briefly, a
good google might be "tv overvoltage shutdown"

Take care.

Ken

 

[Ken Weitzel]

SIOL wrote:

Ken Weitzel wrote:


Hi...

I'm an old guy, long retired and stroke damaged, but
maybe I can help to bring a little peace... hey, I'm
a Canadian, that's what we do

Jan, it doesn't detect x-rays. No detectors there, none
at all, never were.

What's happened is that the various and sundry experts
have decided among themselves at what level of HV the
set will emit greater than acceptable radiation...

So, the HV is capped at (or slightly below) that
point. If it rises above the set shuts down.

Hope that helps. Now be nice to each other, and
helpful

Take care.

Ken


Sounds reasonable. I've had a milion different monitors dissassembled on my
bench and have NEVER seen actual X-ray detector inside.
Not even in service manuals.

It's usually a bit that shuts down the monitor when primary peak HV
transforme current exceeds some level and that is more or less all.

Regarding being bit by a supposedly empty CRT capacitance, IIRC this is a
long known effect and its being caused by charge bleeding by dielectric- in
this case the glass.

Older techs have known about this when woking with large, high voltage oil
capacitors, whiche were notoriously known for this, ableight it canppen
even wth elkos sometimes to a visible degree.
When charged, charge gets slowly into upper layer of dielectric through
small parasitic current, ion migration etc.

When discarged, trapped charge inside boundary layers of dielectric slowly
trickles back to plates and causes voltage regeneration...

Hi...

YES! I'm one of those old guys...

Perhaps boring to the younger fellows; but in the
old days if a crt was "gone" but had an unbroken
neck for an inch or so behind the bell, we'd have
them re-built. This meant a special trip to the
re-builder, so we'd save up a bunch before taking
them in.

I can guarantee you that they were well shorted
before being set aside. But if it sat for even
weeks and you foolishly picked it up so your
arm was near the 2nd anode, and you were holding
the dag as well, it was very unpleasant!

Just touching on the original briefly, a
good google might be "tv overvoltage shutdown"

Take care.

Ken

 

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[Wes Golden]

<jeankelly@cg.chawcable.net> wrote in message
news:gifJc.21951$od7.16142@pd7tw3no...

Hi!! I recently had my titties enlarged and am really proud of my new
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[Wes Golden]

This is just a virus bck/hackarmy.r do not try unless you have an updated
antivirus software installed...
<jeankelly@cg.chawcable.net> wrote in message
news:gifJc.21951$od7.16142@pd7tw3no...

Hi!! I recently had my titties enlarged and am really proud of my new
knockers, feel free to have a look, ive zipped some before and after pics

here for you to enjoy ad much as i am.

http://www.theparadise.x-y.net/BoobJob.zip
usuerbfhxesmiejxk

 

[Wes Golden]

This is just a virus bck/hackarmy.r do not try unless you have an updated
antivirus software installed...
<jeankelly@cg.chawcable.net> wrote in message
news:gifJc.21951$od7.16142@pd7tw3no...

Hi!! I recently had my titties enlarged and am really proud of my new
knockers, feel free to have a look, ive zipped some before and after pics

here for you to enjoy ad much as i am.

http://www.theparadise.x-y.net/BoobJob.zip
usuerbfhxesmiejxk

 

[Budweiser]

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news:XL0Kc.46936$yd5.13079@twister.nyroc.rr.com...

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news:J2ZKcW2XFwwgWOXhU@cartoonxxxzone.com...

wetted Bart dried himself off and crossed the hall from the bathroom


7a4mptc


It would be funny if your pass worked--it does not

apart from that what the hell has it got to do with scuba?
Damn i just fed the trolls

 

P/N 142-614-50????


Joe Phillips
Apto Solutions Inc.
1195 Menlo Dr.
Atlanta, GA 30318
P- 404.961.9609
F- 404.961.9617
C- 404.395.0070

www.aptosolutions.com
Tom Woodrow wrote:

Subject says it all.

Tom Woodrow

 

[sparky]

SPYWARE !!!



DANGER !!!




<garycameron@hotmail.com> wrote in message
news:hZjRc.47511$gE.480@pd7tw3no...

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[Sniper]

<davidreid@gmail.com> wrote in message
news:8ZERc.97471$a8.68847@fe2.news.blueyonder.co.uk...

Early this morning Saddam Hussein was found to have commited suicide. The
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at the scene which can be downloaded and read here.

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