Watson's Weston Meter Mystery

[Jim Adney]

On Tue, 9 Mar 2004 00:29:21 -0800 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

I looked behind the movement and saw the three bobbins that hold the
resistance wire, and how they're connected between the binding posts.
They're connected in series, like this. View with courier font.


3V 150V
o o
| |
- o----[Meter]-----/\/\/\---+----/\/\/\---+----/\/\/\-----o + 300V
R1 R2 R3


Since it's 1000 ohms per volt, the R1 and meter resistance is 3000 ohms.
The other two resistors are about 150k each, but they are not equal, and
they were marked with "150" and "300" when it was put together decades
ago.

If you measure closely, I would expect you to find that:

R2 = 49(Rm + R1)

R3 = 50(Rm + R1)

I'll bet that your measurements are consistent with this, it's just
that you don't have enough resolutio when measuring (Rm + R1).

They are something like 149. something k and 152. something
k.

From the equations above,

R2/R3 = 49/50

Which is exactly what you've got.

The reason they don't come out to the exact numbers you expect is that
the resistors just have to be in some proportion to each other. I
suspect they made up bunches of resistors and meter movements in about
the right ratios and then sorted them to get sets of properly matched
parts.

Alternatively they could have made and measured meter movements,
selected sets of R2 & R3 in exactly the right ratios, and then
selected an R1 to fit them all together.

I suspect that the magnet field strengths in the meter movements were
then tweaked to get the sensitivity right on.

Does anyone know how it was actually done?

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Watson A.Name - \"Watt Su]

"Jim Thompson" <thegreatone@example.com> wrote in message
news:01cs4053kpvdke8r9ksmhsl4rlq8aanvbd@4ax.com...

On Tue, 09 Mar 2004 12:51:06 -0800, "Watson A.Name \"Watt Sun - the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

Jim Thompson wrote:
[snip]


It was 101°F on my patio yesterday, but humidity was 15%.

...Jim Thompson

Yabbut.. That's Arizona! Like the peak temps for So. Calif are the
mean or average for Phoenix!

AND we don't get the severe humidity like you do. 90°+ in the LA
basin in bad-ass.

It's usually dry heat here in LaLa land, just like where you are.
Except it doesn't get so infernally hot! ;-)

...Jim Thompson
--

 

[Robert Baer]

"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Robert Baer wrote:

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:
[snip]

After J.W. clued me in earlier this evening (see followup), I dug the
pitch out of the screw heads with an exacto knife. I got most of it out
and then unscrewed the screws. The cover came off front of the case
easily. But the problem is that the meter is mounted to the case, and
there is nothing protecting the meter movement including the needle, so
one false move, and total catastrophe!

I looked behind the movement and saw the three bobbins that hold the
resistance wire, and how they're connected between the binding posts.
They're connected in series, like this. View with courier font.

3V 150V
o o
| |
- o----[Meter]-----/\/\/\---+----/\/\/\---+----/\/\/\-----o + 300V
R1 R2 R3

Since it's 1000 ohms per volt, the R1 and meter resistance is 3000 ohms.
The other two resistors are about 150k each, but they are not equal, and
they were marked with "150" and "300" when it was put together decades
ago.

Since getting to the bobbins requires that the meter movement be
removed, and I've meddled with and fouled up more than one meter
movement in the past, I'm not going to risk messing this one up, so I
put it back together.

I've decided that the best way to make the mods is to unscrew the four
binding post nuts, put a piece of glass epoxy PCB with four holes in it
over the four screws, and then put the binding post nuts back on. I'll
mount all the resistors on this PCB. I can even put 4 four-way binding
posts on the PCB so it will allow me to use banana plugs for the test
leads.

If I could find one, I could mount a single pole, three position slide
switch on the PCB so I can select the three ranges. Or else just KISS
and just use the binding posts for choosing the ranges, like it is at
present.
[snip]

Yes...all of them are that way; zero meter protection when apart.
And the accuracy is not a pecentage of full-scale like "modern"
analogs, the accuracy is a percentage of the reading *anywhere*; meaning
!superb!.
I bet that (approximately) that R3=R1+R2 and that is why R3 is not
equal to R2.

Yeah, Zackly. But oddly, they're not some even value like I had
supposed. They are something like 149. something k and 152. something
k. The DMMs I'm using don't do such a good job of resolving on the 200k
range.

Have an alternate idea: leave the meter alone and use external
resistors from the 3V terminal.

Um, isn't that what I said I was gonna do?? Above..

What I had to do was calculate the right values for the shunts. The
only problem is that I've already put a 1% fixed resistor and pot across
the 150 V resistor, and then set it to give the correct reading. I then
measured it, and it doesn't match up with the calculations. So I'll
probably just leave it so it's slightly adjustable.

The 150V resistor has 147V across it at FS. That means that for a 1 mA
meter, it should be 147k. But it measures 149. something k. Weird.

Do not forget to take into account the meter resistance; I(full
scale)*(Rm+R1+R2)=150V.
So R2 should have slightly less than 147V across it, since the meter
has (roughly) 200mV drop (wild guess).
Maybe the meter is more sensitive than 1mA full scale, so a larger
resistor is then needed.
Those resistors should be considered as having 0.1% accuracy so a 3.5
digit DVM will not do them justice.
I presume you know the methods of measuring Rm (indirectly).

 

[Robert Baer]

gothika wrote:

On Tue, 9 Mar 2004 00:29:21 -0800, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:


"Robert Baer" <robertbaer@earthlink.net> wrote in message
news:404AE249.5DDAA8AD@earthlink.net...
"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

Watson's Weston Meter Mystery

Help me solve this Weston Meter Mystery. I got this good ol' Weston
Voltmeter at the Antique Telephone Collectors Ass'n show this
weekend,
and it works great on the 3V range. I want to do a little
modifying.
It has three binding posts on the top, 3V, 150V and 300VDC. I want
to
change the resistors on the 150 and/or 300VDC ranges to make them 15
and/or 30VDC. I took the four corner screws out but the case won't
budge. I've attached a pic of it, with the enlarged screwhead that
maybe isn't a screw head, or whatever, and posted it to ABSE. Maybe
someone has had experience with getting these apart. Thanks for any
info.

I have a Weston Microammeter, and the trick to it was to remove the
binding post knobs on the face (meter surface), the range switch on
the
face, then the screws on the back (the zeroing knob remained as a part
of the case), then remove the screws on the back.
In your case, look for "standoff" bumpers on the back and see if
there
are screws hiding underneath.
Seems to me that the back should come off; look for a parting line.

Also carefully and with minimal force, pry it apart when all screws
(except for the "W" screws) are out, to see where the resistance
point(s) may be - in other words, does it seem that the "W" points are
holding?
If it seems that the "W" points are the only remaining fasteners,
try
(a) soak 8 HR+ with lubricating screw-removal liquid (forget the name
now and too lazy do dig it out), (b) make a mold of the head and from
that mold, a screwdriver (plastic or low MP metal to form in mold).
Align the home-made scerwdriver and tap lightly with with hammer (to
help loosen scerw) while turning.
This might work well enough to keep the head shape intact, even if
of
plastic.
Worst case is to break the plastic "W" off and drill the head off;
replace with a screw that has a head that matches the others.

After J.W. clued me in earlier this evening (see followup), I dug the
pitch out of the screw heads with an exacto knife. I got most of it out
and then unscrewed the screws. The cover came off front of the case
easily. But the problem is that the meter is mounted to the case, and
there is nothing protecting the meter movement including the needle, so
one false move, and total catastrophe!

I looked behind the movement and saw the three bobbins that hold the
resistance wire, and how they're connected between the binding posts.
They're connected in series, like this. View with courier font.


3V 150V
o o
| |
- o----[Meter]-----/\/\/\---+----/\/\/\---+----/\/\/\-----o + 300V
R1 R2 R3


Since it's 1000 ohms per volt, the R1 and meter resistance is 3000 ohms.
The other two resistors are about 150k each, but they are not equal, and
they were marked with "150" and "300" when it was put together decades
ago.

Since getting to the bobbins requires that the meter movement be
removed, and I've meddled with and fouled up more than one meter
movement in the past, I'm not going to risk messing this one up, so I
put it back together.

I've decided that the best way to make the mods is to unscrew the four
binding post nuts, put a piece of glass epoxy PCB with four holes in it
over the four screws, and then put the binding post nuts back on. I'll
mount all the resistors on this PCB. I can even put 4 four-way binding
posts on the PCB so it will allow me to use banana plugs for the test
leads.

If I could find one, I could mount a single pole, three position slide
switch on the PCB so I can select the three ranges. Or else just KISS
and just use the binding posts for choosing the ranges, like it is at
present.

That meter movement is unbelievable! It has the mirror behind the
needle to avoid parallax. I connected it to the Power Designs 2005
precision voltage source to see how accurate it was. The 2005 has four
ten-step rotary range switches, one each for volts, tenths, hundredths,
and thousandths of a volt, and a vernier pot that varies it by 1000
microvolts, same as 1 millivolt.

I set it for 3.000 VDC, and varied the vernier pot by 0 to 1000
microvolts. The meter needle is very thin, less than a third of the
black line on the meter scale that indicates 3 volts. Using a
magnifying glass, I can *easily see* the meter needle moving across the
black line maybe a quarter of the line width! I can actually see it
moving as I vary the pot by a few hundred microvolts! Wow! A wiggle
stick meter than can resolve a change of microvolts!

Now I know why those old Wheatstone bridges used a galvanometer with a
needle that cast a shadow on an illuminated scale, and using mirrors,
the light path was lengthened to maybe several feet in a small case. So
it allowed the ever so tiny meter needle movements to be magnified and
easily seen on the scale.

Someone insert a URL with pictures here explaining these old galvos, and
how they worked. It's late and I'm getting bleary-eyed.



I started out my photographic carreer using those old Weston light
meters and never got a bad reading once. Those things were built like
tanks.

I still have two..

 

[Robert Baer]

Jim Adney wrote:

On Tue, 9 Mar 2004 00:29:21 -0800 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

I looked behind the movement and saw the three bobbins that hold the
resistance wire, and how they're connected between the binding posts.
They're connected in series, like this. View with courier font.


3V 150V
o o
| |
- o----[Meter]-----/\/\/\---+----/\/\/\---+----/\/\/\-----o + 300V
R1 R2 R3


Since it's 1000 ohms per volt, the R1 and meter resistance is 3000 ohms.
The other two resistors are about 150k each, but they are not equal, and
they were marked with "150" and "300" when it was put together decades
ago.

If you measure closely, I would expect you to find that:

R2 = 49(Rm + R1)

R3 = 50(Rm + R1)

I'll bet that your measurements are consistent with this, it's just
that you don't have enough resolutio when measuring (Rm + R1).

They are something like 149. something k and 152. something
k.

From the equations above,

R2/R3 = 49/50

Which is exactly what you've got.

The reason they don't come out to the exact numbers you expect is that
the resistors just have to be in some proportion to each other. I
suspect they made up bunches of resistors and meter movements in about
the right ratios and then sorted them to get sets of properly matched
parts.

Alternatively they could have made and measured meter movements,
selected sets of R2 & R3 in exactly the right ratios, and then
selected an R1 to fit them all together.

I suspect that the magnet field strengths in the meter movements were
then tweaked to get the sensitivity right on.

Does anyone know how it was actually done?

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

More likely each resistor set was wound for a given meter.

 

[Robert Baer]

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Jim Adney" <jadney@vwtype3.org> wrote in message
news:5v4t40teul8vtqdcrafbt7jhu7vvgrumn1@4ax.com...
On Tue, 9 Mar 2004 00:29:21 -0800 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

I looked behind the movement and saw the three bobbins that hold the
resistance wire, and how they're connected between the binding posts.
They're connected in series, like this. View with courier font.


3V 150V
o o
| |
- o----[Meter]-----/\/\/\---+----/\/\/\---+----/\/\/\-----o + 300V
R1 R2 R3


Since it's 1000 ohms per volt, the R1 and meter resistance is 3000
ohms.
The other two resistors are about 150k each, but they are not equal,
and
they were marked with "150" and "300" when it was put together
decades
ago.

If you measure closely, I would expect you to find that:

R2 = 49(Rm + R1)

R3 = 50(Rm + R1)

I'll bet that your measurements are consistent with this, it's just
that you don't have enough resolutio when measuring (Rm + R1).

The meter and 3V resistor measure 3k as would be expected, since it's a
1 mA movement.

They are something like 149. something k and 152. something
k.

From the equations above,

R2/R3 = 49/50

Which is exactly what you've got.

I calculated 147k and 150k. I measured 149 and a fraction K, and 152
and a fraction k. Not the same.

The reason they don't come out to the exact numbers you expect is that
the resistors just have to be in some proportion to each other. I
suspect they made up bunches of resistors and meter movements in about
the right ratios and then sorted them to get sets of properly matched
parts.

Well, yeah, if the meter movement was more sensitive than 1 mA. But
then the 3V range would also measure proportionately greater than 3k.

Alternatively they could have made and measured meter movements,
selected sets of R2 & R3 in exactly the right ratios, and then
selected an R1 to fit them all together.

I suspect that the magnet field strengths in the meter movements were
then tweaked to get the sensitivity right on.

Does anyone know how it was actually done?

Maybe the bobbins, which are wound with high resistance wire, have a
voltage sensitivity. Or else since they are old, they may have changed
resistance.
The sticker on the front said it was supposed to be recal'd in 1975.
The meter itself may be a lot older than that.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

Those resistors did not have a voltage sensitivity that you could see,
and they are wire wound, using a low TC wire, and essentially do not
change.

 

[TekMan]

Jim Yanik <jyanik@abuse.gov> wrote in message news:<Xns94A7C48C59EDCjyanikkuanet@204.117.192.21>...
...snipped..

I'm just brainstorming; I've never even seen a scope calibrator, I
don't know what they do or what the issues are. Anyone care to chip
in?




TEK's PG506 has a fast rise output for freq.compensation and leading edge
cal,>1ns at 0-1vPP into 50 ohms,100 Hz-1Mhz in decade steps,then it has a
hi-amplitude output,0-60V,for adjusting attenuator comps,also 100Hz-
1Mhz,and the standard amplitude output,5mv-100V (into 1MegR)1Khz sq.wave
for amplitude cal of the attenuators.(in 1-2-5 steps)
Then there's the TG501 timemark generator,1ns to 5sec(IIRC) for timebase
cal,then there's the SG503 leveled sinewave generator,50Khz to 250 Mhz.for
freq.response verification.

That's was TEK's cal package for scopes to 250Mhz.

And all nicely portable in TM503 mainframe - dam..., I love this stuff
even nowadays. You can do so much good work with it.

Andreas

 

[TekMan]

Jim Yanik <jyanik@abuse.gov> wrote in message news:<Xns94A6E015C728Bjyanikkuanet@204.117.192.21>...

"BFoelsch" <BFoelsch@snet.ditch.this.net> wrote in
news:7_ydnWdTrK1eKNHdRVn-gQ@giganews.com:

I don't know, I would guess $100 USD to be about the top end,
considering that you can get brand new hobby quality scopes for $500
or so.

I never have issues with time bases, the problem for me is the
vertical response, and getting a really flat topped square wave.
Heathkit made some hobbyist calibrators, they were OK for time base
and DC stuff but the output had too much noise for serious vertical
channel calibration work.

Actually, I have rarely seen a Tek scope drift seriously out of
calibration, unless you go back to the all-tube era stuff. Even the
later Tek hybrid stuff holds its calibration remarkably well. Can't
say the same about the old HP stuff, though.

I sure have seen a lot of 400 series TEK scopes "seriously out of
cal",especially the attenuators.Same for 7K series. Resistors change
value,changing gains and offsets,some were underrated for the power they
dissipated.And some folks would 'blast' attenuators and FET front ends,too.

Now the 2445/65 series were the best,most stable,and accurate scopes TEK
ever made.
Too bad TEK had to sell off the IC/hybrid manufacturing unit;that killed
all the 2400 series scopes. I tried to warn 'em about that one,well before
they did it.DAMN them TEK beancounters!

I agree with Jim: It just depends on how many Tek 4xx scopes you have
got in your hands. Statisticaly, these units are very stable and keep
their accuracy better than a lot of other brands. Well, in 1973 to
1984 (tek 465 - 465M -465B) you had to pay 2200 to 3100 USD for such a
scope -- and you got quality.

scnr,
Andreas

 

[Rich Andrews.]

Jim Yanik <jyanik@abuse.gov> wrote in news:Xns94A6E0FBD4958jyanikkuanet@
204.117.192.21:

Jay Levitt <jay+news@jay.fm> wrote in
news:MPG.1ab6a73d788d1043989729@news-central.giganews.com:

In article <Xns94A67D3F0F59Fjyanikkuanet@204.117.192.21>,
jyanik@abuse.gov says...

I wonder what people would pay for a hobbyist scope calibrator? One
that's not NIST-traceable,but reasonable accuracy,for low-end
scopes.(not 500 Mhz and up)
$100,$200 USD?
The time-mark section is the easiest to build.

I'd pay $100 for it.. but how do you keep the calibrator calibrated?


Good quality DMM and a freq.counter locked to WWVB.
I don't believe one could be made for sale at $100 and still make a
profit,though.Maybe $200.

FYI,Nut's and Volts magazine had an article on making your own timebase
calibrator using inexpensive,off-the shelf parts a few years ago.Maybe
$20
worth of parts.Electronic Goldmine used to offer a kit for it.

I have a timebase for a HP 5245L if anyone is interested. It has about 30
minutes of run time on it.

r


--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.

 

[Mark Fergerson]

ns wrote:

There is another option here: he is pulling your leg.

I know. But on the off chance that he's serious, consider
that he might decide that since nobody will come to his
rescue, he might as well get a gun and start blasting the
many people he's "identified" as his tormentors.

Better that he fritter away his time learning some
physics and electronics than occupying a prison cell (or
execution apparatus), and his potential murder victims their
graves.

Mark L. Fergerson

 

[Frank Bemelman]

"Mark Fergerson" <nunya@biz.ness> schreef in bericht
news:OIH3c.4420$Nj.3595@fed1read01...

ns wrote:

There is another option here: he is pulling your leg.

I know. But on the off chance that he's serious, consider
that he might decide that since nobody will come to his
rescue, he might as well get a gun and start blasting the
many people he's "identified" as his tormentors.

Better that he fritter away his time learning some
physics and electronics than occupying a prison cell (or
execution apparatus), and his potential murder victims their
graves.

Or is he selling his soda cans on Ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3665036068&category=13604&sspagename=STRK%3AMEBWA%3AIT&rd=1


--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)

 

[Peter Bennett]

On Tue, 9 Mar 2004 23:38:32 -0800, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

The meter and 3V resistor measure 3k as would be expected, since it's a
1 mA movement.

They are something like 149. something k and 152. something
k.

From the equations above,

R2/R3 = 49/50

Which is exactly what you've got.

I calculated 147k and 150k. I measured 149 and a fraction K, and 152
and a fraction k. Not the same.

That is only an error of about 1.3% - what is the guaranteed accuracy
of your meter, and when was it last calibrated?

Your meter is showing the right difference between the resistor
values, but I suspect that the meter is just reading a little high.

Digital meters allow you to read the wrong value with great precision



--
Peter Bennett VE7CEI
email: peterbb (at) interchange.ubc.ca
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

 

[Jim Adney]

On Tue, 9 Mar 2004 23:38:32 -0800 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

The meter and 3V resistor measure 3k as would be expected, since it's a
1 mA movement.

3k or 3000 Ohms? If it was actually 3001 Ohms that might be all the
difference you'd need. How accurate is your Ohmmeter?

The movement could be a .998 mA movement or a 1.002 mA movement and
the only way we'd know the difference would be with a precision
current source.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Watson A.Name - \"Watt Su]

"Peter Bennett" <peterbb@nowhere.invalid> wrote in message
news:gmuu40dcb03fncttplt21dvfpintprpd0h@4ax.com...

On Tue, 9 Mar 2004 23:38:32 -0800, "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:


The meter and 3V resistor measure 3k as would be expected, since it's
a
1 mA movement.

They are something like 149. something k and 152. something
k.

From the equations above,

R2/R3 = 49/50

Which is exactly what you've got.

I calculated 147k and 150k. I measured 149 and a fraction K, and 152
and a fraction k. Not the same.


That is only an error of about 1.3% - what is the guaranteed accuracy
of your meter, and when was it last calibrated?

Your meter is showing the right difference between the resistor
values, but I suspect that the meter is just reading a little high.

Digital meters allow you to read the wrong value with great precision

Good point. So I did the measurements again. View with Courier font


Meter used --> Fluke 77 B&K 2707 B&K 389

3V resistor + meter 2.998 k 3.00 k 2.996 k

150V resistor 152.7 k 152.4 k 152.6 k

300V resistor 149.9 k 149.6 k 149.8 k

The readings still didn't make sense so I opened up the meter again and
retraced down the wires. I believe I goofed the first time, so I'm
redrawing the schematic. Again, use courier font.


+----/\/\/\---o 3V
|
|
| +--o 150V
| |
- o---[meter]----+----/\/\/\----+----/\/\/\----o 300V
1 mA

What's puzzling me more now is that with the 3V resistor not in series
with the other resistors, there seems no need for the other resistors to
be different in value. But they still are.

Bleah!!

--
Peter Bennett VE7CEI
email: peterbb (at) interchange.ubc.ca
GPS and NMEA info and programs:
http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

 

[Watson A.Name - \"Watt Su]

"BFoelsch" <BFoelsch@snet.ditch.this.net> wrote in message
news:e8-dnW-zk8mw083dRVn-jQ@giganews.com...

Why don't you hook up a voltage source and see if the 150V and 300V
ranges
are perfectly accurate. If you can't tell, it doesn't matter!

The rules concerning voltage dividers are pretty well established by
now!
You are looking at errors of around 1% in a 60 year old instrument
that was
probably rated at 1% to begin with.

True. The reason for the measurement was to get a value with which to
calculate the value of the shunt resistor to bring it down to 15 and 30
volts. So if the old values are not correct, that's not really
important, as long as the totals are correct. But to all, thanks for
the observations and advice.

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:1050a5r8uolj0d2@corp.supernews.com...

"Peter Bennett" <peterbb@nowhere.invalid> wrote in message
news:gmuu40dcb03fncttplt21dvfpintprpd0h@4ax.com...
On Tue, 9 Mar 2004 23:38:32 -0800, "Watson A.Name - \"Watt Sun,
the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:


The meter and 3V resistor measure 3k as would be expected, since
it's
a
1 mA movement.

They are something like 149. something k and 152. something
k.

From the equations above,

R2/R3 = 49/50

Which is exactly what you've got.

I calculated 147k and 150k. I measured 149 and a fraction K, and
152
and a fraction k. Not the same.


That is only an error of about 1.3% - what is the guaranteed
accuracy
of your meter, and when was it last calibrated?

Your meter is showing the right difference between the resistor
values, but I suspect that the meter is just reading a little
high.

Digital meters allow you to read the wrong value with great
precision


Good point. So I did the measurements again. View with Courier
font


Meter used --> Fluke 77 B&K 2707 B&K 389

3V resistor + meter 2.998 k 3.00 k 2.996 k

150V resistor 152.7 k 152.4 k 152.6 k

300V resistor 149.9 k 149.6 k 149.8 k

The readings still didn't make sense so I opened up the meter again
and
retraced down the wires. I believe I goofed the first time, so I'm
redrawing the schematic. Again, use courier font.


+----/\/\/\---o 3V
|
|
| +--o 150V
| |
- o---[meter]----+----/\/\/\----+----/\/\/\----o 300V
1 mA

What's puzzling me more now is that with the 3V resistor not in
series
with the other resistors, there seems no need for the other
resistors to
be different in value. But they still are.

Bleah!!

--
Peter Bennett VE7CEI
email: peterbb (at) interchange.ubc.ca
GPS and NMEA info and programs:
http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

 

[Jim Yanik]

"Tom Del Rosso" <tdnews01@att.net.invalid> wrote in
news:0q24c.2486$H44.43833@bgtnsc04-news.ops.worldnet.att.net:

In news:Xns94A6E015C728Bjyanikkuanet@204.117.192.21,
Jim Yanik typed:

Too bad TEK had to sell off the IC/hybrid manufacturing unit;that
killed all the 2400 series scopes. I tried to warn 'em about that
one,well before they did it.DAMN them TEK beancounters!

And, because it was an obsolete fab, whoever bought it probably scrapped
it soon after.

No,they kept the process,but stopped making the "TEK-made" IC's for TEK
because of the low volume of parts bought by TEK.
Actually,the TEK IC processes were,I believe,state-of-the-art at that time.
Maxim was the company that bought the TEK ICO/Hybrid line.

Triquint Semiconductors,still in business,was spun off by TEK many years
ago.

--
Jim Yanik
jyanik-at-kua.net

 

[RCC boy]

I bought a programmer from this site a year ago.
It works very well.

http://www.geocities.com/hughesinnovations/urp.html

Jason


"Richard W. Solomon, W1KSZ" <w1ksz@earthlink.net> wrote in message
news:r80i409g0n07em88k9o84hql8o3181t70g@4ax.com...

Looking for an EPROM Programmer, something like the
the Needhams EMP-10 would be ideal.

Thanks, Dick, W1KSZ

 

[Jim Adney]

On Thu, 11 Mar 2004 00:53:17 -0800 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

+----/\/\/\---o 3V
|
|
| +--o 150V
| |
- o---[meter]----+----/\/\/\----+----/\/\/\----o 300V
1 mA

What's puzzling me more now is that with the 3V resistor not in series
with the other resistors, there seems no need for the other resistors to
be different in value. But they still are.

I agree. I liked your first iteration better, too.

How sure are you this time? ;-)

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Tobin Fricke]

On Fri, 5 Mar 2004, Tobin Fricke wrote:

I have an old (from 1984) GPIB-PC interface card from National
Instruments, an 8-bit ISA interface card to the IEEE-488 / GPIB / HPIB
instrumentation bus.

It turns out that version C13 "for 488.1 boards"[1] of the GPIB-PCII/IIA
driver works with this board ("ASSY180100-02 REV G", "GPIB-PC",
"National Instruments, (c) 1984").

Tobin Fricke

[1] ftp://ftp.ni.com/support/gpib/doswin3/gpib-pcii.iia/488.1/

 

[Watson A.Name \"Watt Sun]

Jim Adney wrote:

On Thu, 11 Mar 2004 00:53:17 -0800 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

+----/\/\/\---o 3V
|
|
| +--o 150V
| |
- o---[meter]----+----/\/\/\----+----/\/\/\----o 300V
1 mA

What's puzzling me more now is that with the 3V resistor not in series
with the other resistors, there seems no need for the other resistors to
be different in value. But they still are.

I agree. I liked your first iteration better, too.

How sure are you this time? ;-)

Yeah, I measured once and cut twice this time. ;-) I double checked
the wiring, and even tho all the wires are uniformly black and pass
behind things that hide them, I'm reasonably certain of it this time.

I drilled some holes in a piece of bare PCB and removed the binding post
nuts, and it fits over the binding posts okay. I'll have to drill some
more homes in it for some more binding posts and buy a few more binding
posts from ratio snack. That way I'll have some holes to poke banana
plugs into instead of having to use bare wires.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------