Re: [volt-nuts] Looking for Fluke 845AB manual
Charles:
I have a Fluke 845AB original manual P/N 294173 dated November
- In comparing the "pdf" file "845A_AB_imeng0000.pdf", which is
also a scan of P/N 294173, which I downloaded from the Fluke website
sometime back and I find that this file is missing pages:
2-2
2-3
2-4
2-5
3-2
4-4
4-5
4-6
5-1
5-2
It also seems to be missing 1/2 of the schematic from the "dark
blobs", and to the right.
However the Fluke file does have a newer "Change/Errata
Information" sheet than I have.
If you still need these pages I can scan them into a "pdf" and
email them to you. You will have to do a "cut and paste" on the
schematic as I can only scan 8 1/2x 11 and the schematic is 8 1/2 x
34 inches, or 4 pages across.
Let me know.
Bill
You can purchase a complete high quality PDF of the 845A/AB manual from Dave
Henderson at http://www.artekmedia.com . I just purchased a download of the
manual for $10 US, and can vouch for its quality. Very clear scans, with
NO MISSING PAGES. It's P/N 294173, dated November 1967 copyright 1981.
Along the same thread, as Bill notes, there is a change/errata note in the
manual on Fluke's website that says:
A major circuit modification has been made to the Fluke Model 845AB. This
change entails the complete redesign of the Photo Modulator, previously
based on photo-conductive resistors. The new circuit now employs
optically-isolated Bilateral Analog FETs, and is fabricated on an additional
circuit board.
Updates to the relevant sections of this manual are now in process and will
be available for shipment approximately December 1993. This manual is
completely accurate with regard to specifications and operating
instructions. The circuit modifications are totally internal and are
completely transparent to the user.
If you have any questions regarding repair and/or service of your 845AB
please contact your nearest Fluke Service Center (see the list attached to
this change/errata.)
Does anyone have any info on the design changes described in the errata
note? The old photo modulator/demodulator design used by Fluke and HP is
troublesome due to deteriation of the photoresistors and neon bulbs, I
surely would like to see a schematic & parts list of the design change.
I'll bet the new circuit could be used in many of the Fluke differential
voltmeters, too.
David
dgminala at mediacombb dot net
David wrote:
You can purchase a complete high quality PDF of the 845A/AB manual
from Dave Henderson at http://www.artekmedia.com . I just purchased
a download of the manual for $10 US, and can vouch for its
quality. Very clear scans, with NO MISSING PAGES. It's P/N
294173, dated November 1967 copyright 1981.
I have a couple of the Artek manuals. I agree they are nice scans,
but I will never buy another one until they quit maxing out the
password security. The ones I have are screwed down so tight you
can't even rotate the pages to look at sideways schematics right-side
up on the monitor. All I care about is the original manual
contents. I don't care about the added features (OCR, bookmarking,
whatever) -- in fact, I'd prefer that they weren't there, so I didn't
have to close the bookmark window every time I opened the
manual. But you can't even use the basic scans as intended because
of the insane security. Anyone who is that paranoid about his
product can keep it.
as Bill notes, there is a change/errata note in the manual on
Fluke's website that says:
A major circuit modification has been made to the Fluke Model 845AB.
This change entails the complete redesign of the Photo Modulator,
previously based on photo-conductive resistors. The new circuit now
employs optically-isolated Bilateral Analog FETs, and is fabricated
on an additional circuit board.
Does anyone have any info on the design changes described in the
errata note? The old photo modulator/demodulator design used by
Fluke and HP is troublesome due to deteriation of the photoresistors
and neon bulbs, I surely would like to see a schematic & parts list
of the design change.
Does anybody know with certainty if Fluke actually made any of the
FET-switched units?
Best regards,
Charles
ps. Another list member has kindly contributed scans of the missing
pages for the 845A/AB manual. I will assemble a complete PDF and see
that it is uploaded to Didier's site, but it may take me a week or two.
Fellow voltage aficionados ,
If this has already been discussed - my apologies. I could not find
this topic in the past several months of list archives.
Like many of us, I have an ever growing collection of voltmeters and
related instruments. Like the man with two clocks who is never sure of
the time, I now have enough volt meters to have doubts about all of them.
So - I was wondering if those on this list with really good voltage
measurement capabilities would be willing to help those of us without.
What I have in mind is creating a small voltage reference circuit based
on one of the many available IC references that is stable enough in both
time and temperature to use as a transfer standard. I am thinking that
the actual voltage is not important, just the stability. Using the ICs
that I am familiar with the actual reference voltage would be around 5,
7, or 10 volts. Said reference would be mailed to a willing list member
who would record his reading of the reference and mail it back.
I don't have such a reference yet, but have breadboarded a couple and
the idea seems like it might work.
My first objective would be to obtain a reference that I could use to
get all my meters to agree. Since the best meters I have are an HP3455A
(best accuracy about 20 - 40 ppm, and only for 24 hours) and an ancient
(but very usable) Fluke 883AB (best accuracy is 100ppm), I would be very
happy to have a reference that I could trust to 10ppm.
So - two questions for the list:
-
Does this sound feasible? Am I overlooking anything that would keep
me from being able to transfer a 10ppm known reference? -
Any list members that would be willing to help with this? I
envision mailing a small package with the reference in it along with an
enclosed, postage paid, return box. I am asking for a member that would
take the reference, apply power, let it warm up, record the room
temperature and the reference voltage to within 10ppm, and return it to
me. If you prefer to respond off-list - smither@c-c-i.com.
BTW - I live in Friendswood, Texas (near Houston). Any fellow nutters
close enough that I could hand deliver the reference?
Best regards,
Bob Smither
Just a quick off-the-cuff thought: has anyone considered building a
voltage reference into the oven of a deceased OCXO? That would give you
a very stable thermal environment for very little work.
John
On 8/25/2011 1:14 PM, Bob Smither wrote:
Fellow voltage aficionados ,
If this has already been discussed - my apologies. I could not find this
topic in the past several months of list archives.
Like many of us, I have an ever growing collection of voltmeters and
related instruments. Like the man with two clocks who is never sure of
the time, I now have enough volt meters to have doubts about all of them.
So - I was wondering if those on this list with really good voltage
measurement capabilities would be willing to help those of us without.
What I have in mind is creating a small voltage reference circuit based
on one of the many available IC references that is stable enough in both
time and temperature to use as a transfer standard. I am thinking that
the actual voltage is not important, just the stability. Using the ICs
that I am familiar with the actual reference voltage would be around 5,
7, or 10 volts. Said reference would be mailed to a willing list member
who would record his reading of the reference and mail it back.
I don't have such a reference yet, but have breadboarded a couple and
the idea seems like it might work.
My first objective would be to obtain a reference that I could use to
get all my meters to agree. Since the best meters I have are an HP3455A
(best accuracy about 20 - 40 ppm, and only for 24 hours) and an ancient
(but very usable) Fluke 883AB (best accuracy is 100ppm), I would be very
happy to have a reference that I could trust to 10ppm.
So - two questions for the list:
-
Does this sound feasible? Am I overlooking anything that would keep
me from being able to transfer a 10ppm known reference? -
Any list members that would be willing to help with this? I envision
mailing a small package with the reference in it along with an enclosed,
postage paid, return box. I am asking for a member that would take the
reference, apply power, let it warm up, record the room temperature and
the reference voltage to within 10ppm, and return it to me. If you
prefer to respond off-list - smither@c-c-i.com.
BTW - I live in Friendswood, Texas (near Houston). Any fellow nutters
close enough that I could hand deliver the reference?
Best regards,
Bob Smither
volt-nuts mailing list -- volt-nuts@febo.com
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In message 4E56863A.7040708@febo.com, John Ackermann N8UR writes:
Just a quick off-the-cuff thought: has anyone considered building a
voltage reference into the oven of a deceased OCXO? That would give you
a very stable thermal environment for very little work.
I played with temperature stabilizing a MAX6250 with a peltier. The
results were quite promising, but I ran out of round tuits.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Hello Bob,
Im experimenting for some years with different references.
For a traveling reference with 10ppm I would use a heated reference like a
LM399.
You will find it in most of the serious 6,5 Digit Multimeters like HP34401A
or Keithley 2000.
I use them battery powered (NIMH-Cells) with a voltage stabilizer.
(the heater voltage has some influence on the output voltage).
Time stability can be determined by building several of them pre-ageing for
some 1000 hours
and then sorting out the extremes.
Of my 2 LM399s one is running pretty close to 2 LTZ1000A references
the other (a desoldered part from a old measurement card) is drifting around
by +/-25uV.
For unheated references like a MAX6250 you will have to determine the
temperature
very exactly. I use NTCs mounted directly at the ground pin of the Reference
to get
nearly the temperature of the reference with a resolution of 0.1 K.
When selecting some 3rd order compensated LT1027CCN8-5 references
you will be able to find some with a low TC near room temperature.
But all plastic references suffer from 2 things:
first: mechanical stress will shift output voltage.
So I solder only one pin directly to the pcb the others with thin wires
So for a traveling reference you will run into trouble.
2nd: when having calibrated the temperature out humidity will play a role.
On my LT1027 the humidity change is around 0.4ppm for each per cent of
relative humidity.
so for a change of 30% you will not get your 10ppm level.
The problem is that the humidity shift has a long time constant. Which is
around 4 or 7 days
with my 2 LT1027 references. So you will have to record the history.
With best regards
Andreas
----- Original Message -----
From: "Bob Smither" smither@c-c-i.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, August 25, 2011 7:14 PM
Subject: [volt-nuts] Traveling Standards
Fellow voltage aficionados ,
If this has already been discussed - my apologies. I could not find
this topic in the past several months of list archives.
Like many of us, I have an ever growing collection of voltmeters and
related instruments. Like the man with two clocks who is never sure of
the time, I now have enough volt meters to have doubts about all of them.
So - I was wondering if those on this list with really good voltage
measurement capabilities would be willing to help those of us without.
What I have in mind is creating a small voltage reference circuit based
on one of the many available IC references that is stable enough in both
time and temperature to use as a transfer standard. I am thinking that
the actual voltage is not important, just the stability. Using the ICs
that I am familiar with the actual reference voltage would be around 5,
7, or 10 volts. Said reference would be mailed to a willing list member
who would record his reading of the reference and mail it back.
I don't have such a reference yet, but have breadboarded a couple and
the idea seems like it might work.
My first objective would be to obtain a reference that I could use to
get all my meters to agree. Since the best meters I have are an HP3455A
(best accuracy about 20 - 40 ppm, and only for 24 hours) and an ancient
(but very usable) Fluke 883AB (best accuracy is 100ppm), I would be very
happy to have a reference that I could trust to 10ppm.
So - two questions for the list:
-
Does this sound feasible? Am I overlooking anything that would keep
me from being able to transfer a 10ppm known reference? -
Any list members that would be willing to help with this? I
envision mailing a small package with the reference in it along with an
enclosed, postage paid, return box. I am asking for a member that would
take the reference, apply power, let it warm up, record the room
temperature and the reference voltage to within 10ppm, and return it to
me. If you prefer to respond off-list - smither@c-c-i.com.
BTW - I live in Friendswood, Texas (near Houston). Any fellow nutters
close enough that I could hand deliver the reference?
Best regards,
Bob Smither
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
One point for LM399:
The output voltage is dependant of the orientation
of the reference. So do not forget to write
Top and Bottom on the carrying case.
My references have a shift of 20-30uV (3-4ppm) with orientation.
On a Keithley 2000 I have noticed a shift of 70uV for a 5V input voltage.
With best regards
Andreas
It is allready difficult to get a home made Vref stable in my own home.
I think it must be possible to do it but it must be build very stable
and oven controlled, in that case humidity will have less influence too
(I think)
No use of potentiometers. I use them in a homebuild one. To fine adjust
you do not need a screwdriver, it I can do it by tapping on the
cabinet ;-)
It is a nice plan (not for me, shipping will be no fun from here and I
have some references) That way you can make your own and calibrate it to
the know one.
I have a solartron 7601, I hook it up to my Westoncells and calibrate
the meter that way. (in the cal menu you can tell the meter what the
refernce voltage is you feeding the meter. I know the value of my cells
(worst case within 10uV) so this is a handy way. I then monitor my 332
or 735A with that meter so I know the correction.
Fred
Andreas Jahn schreef op do 25-08-2011 om 21:41 [+0200]:
Hello Bob,
Im experimenting for some years with different references.
For a traveling reference with 10ppm I would use a heated reference like a
LM399.
You will find it in most of the serious 6,5 Digit Multimeters like HP34401A
or Keithley 2000.
I use them battery powered (NIMH-Cells) with a voltage stabilizer.
(the heater voltage has some influence on the output voltage).
Time stability can be determined by building several of them pre-ageing for
some 1000 hours
and then sorting out the extremes.
Of my 2 LM399s one is running pretty close to 2 LTZ1000A references
the other (a desoldered part from a old measurement card) is drifting around
by +/-25uV.
For unheated references like a MAX6250 you will have to determine the
temperature
very exactly. I use NTCs mounted directly at the ground pin of the Reference
to get
nearly the temperature of the reference with a resolution of 0.1 K.
When selecting some 3rd order compensated LT1027CCN8-5 references
you will be able to find some with a low TC near room temperature.
But all plastic references suffer from 2 things:
first: mechanical stress will shift output voltage.
So I solder only one pin directly to the pcb the others with thin wires
So for a traveling reference you will run into trouble.
2nd: when having calibrated the temperature out humidity will play a role.
On my LT1027 the humidity change is around 0.4ppm for each per cent of
relative humidity.
so for a change of 30% you will not get your 10ppm level.
The problem is that the humidity shift has a long time constant. Which is
around 4 or 7 days
with my 2 LT1027 references. So you will have to record the history.
With best regards
Andreas
----- Original Message -----
From: "Bob Smither" smither@c-c-i.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Thursday, August 25, 2011 7:14 PM
Subject: [volt-nuts] Traveling Standards
Fellow voltage aficionados ,
If this has already been discussed - my apologies. I could not find
this topic in the past several months of list archives.
Like many of us, I have an ever growing collection of voltmeters and
related instruments. Like the man with two clocks who is never sure of
the time, I now have enough volt meters to have doubts about all of them.
So - I was wondering if those on this list with really good voltage
measurement capabilities would be willing to help those of us without.
What I have in mind is creating a small voltage reference circuit based
on one of the many available IC references that is stable enough in both
time and temperature to use as a transfer standard. I am thinking that
the actual voltage is not important, just the stability. Using the ICs
that I am familiar with the actual reference voltage would be around 5,
7, or 10 volts. Said reference would be mailed to a willing list member
who would record his reading of the reference and mail it back.
I don't have such a reference yet, but have breadboarded a couple and
the idea seems like it might work.
My first objective would be to obtain a reference that I could use to
get all my meters to agree. Since the best meters I have are an HP3455A
(best accuracy about 20 - 40 ppm, and only for 24 hours) and an ancient
(but very usable) Fluke 883AB (best accuracy is 100ppm), I would be very
happy to have a reference that I could trust to 10ppm.
So - two questions for the list:
-
Does this sound feasible? Am I overlooking anything that would keep
me from being able to transfer a 10ppm known reference? -
Any list members that would be willing to help with this? I
envision mailing a small package with the reference in it along with an
enclosed, postage paid, return box. I am asking for a member that would
take the reference, apply power, let it warm up, record the room
temperature and the reference voltage to within 10ppm, and return it to
me. If you prefer to respond off-list - smither@c-c-i.com.
BTW - I live in Friendswood, Texas (near Houston). Any fellow nutters
close enough that I could hand deliver the reference?
Best regards,
Bob Smither
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
----- Original Message -----
From: "Fred" pa4tim@gmail.com
No use of potentiometers. I use them in a homebuild one. To fine adjust
you do not need a screwdriver, it I can do it by tapping on the
cabinet ;-)
Thats one reason why I power the references from batteries within the
cabinet.
Of couse you will have to decouple/rf-filter the output of the reference
too.
(Carefully so that the reference does not oscillate).
with best regards
Andreas
Dear All,
Thank you so much for the great responses! You have all given me a lot
to think about.
Andreas mentioned the lm339. One candidate I am considering is the
lm119ah. Of the references I have at hand (lm119a, lt1027bcn, and
max6350cpa) the lm119a looks the most promising. Andreas mentioned that
humidity and stress can cause several ppm errors. The lm119a is in a
hermetic to-46 package in a thermal shield - so hopefully those effects
will be minimized. The idea that the orientation matters is a new one
for me. I will be sure to mark "TOP" on the final package.
Fred advised against the use of pots. I agree. I was thinking of just
using the raw reference output. For my purposes, I don't really care
what the voltage is as long as it is stable and can withstand shipping.
Warren - I appreciate the offer of a 1n825, but the TC is too large for
this purpose. I also suspect it will be noisier than the lm119a.
Dick and Charles M. - thanks for offering help with this project! I
will contact you off list for your address when I have a traveling unit
prepared and will welcome your measurements of it.
Charles S. - your understanding is correct - I would ship the unit to
anyone that is willing to measure it for me. You idea of shipping it
powered up deserves some more thought. One concern I had about this was
the added weight of the batteries for shipping. It may be an even trade
against having a transformer / rectifier / capacitor to make the
required power supply level.
Thanks all! Now to do some serious design and construction.
Bob Smither