Mark Sims | 18 Nov 01:44 2014
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Fluke 5200a extender

I recently bought a small insulation tester DMM off of Ebay ($20, search for "bm500a insulation tester"). 
It can test at 250/500/1000V.  I built up three of the 5200A extender cables and tested them.  There were no
problems at 1000V (even though the ribbon cables are only rated for 300V and there are some pretty tight
clearances on the boards where etches are routed between pins of the ribbon cable headers).  It looks like
there should be no problem handling the max 190V potential difference between two adjacent pins on the
5200A bus.
I tested the cables by shorting all the top side pins and shorting all the bottom side pins on an edge
connector,  hooking the completed extenders to that edge connector,  and testing the resistance between
the top side and bottom sides.  That tests all the adjacent wires on the ribbons and the tight clearances.   		
	   		  
Frank Stellmach | 15 Nov 16:53 2014
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Precision resistor testing

Richard,

if you need to measure the T.C.s of your assemblies, then your 3458A is 
stable enough to do that nice volt-nuts project. You only need a 
temperature stable environment, a precise thermometer (PT100, precision 
NTC), a 2nd DMM for the thermometer, and data acquisition.

I also have done these delicate measurements on Vishay VHP202Z with high 
stability that way. Also important was the good coupling between the DUT 
and the thermometer, and also that they were having a thermal mass (alu 
block and alu case). See Andreas' thread and my setup here:
http://www.eevblog.com/forum/projects/t-c-measurements-on-precision-resistors/30/

As this is a relative measurement, this T.C. measurement can be easily 
done with an uncalibrated 3458A also.

After that, it should be relatively easy to find a cheap possibility to 
measure the absolute value of these reistors at a certain temperature. 
That would fully characterize the resistors.

Frank
Mark Sims | 15 Nov 02:42 2014
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Precision resistor testing

Just for grins I asked IET what it would cost to calibrate my SR104 resistor and they quoted something like
$1000.   I did not respond and a couple of weeks later they sent an email along the lines of "Hey if that was too
much, let's talk... we can work out a price..." 		 	   		  
Richard Moore | 14 Nov 23:36 2014
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Precision resistor testing

I’ve built a little box with two 10kohm precision resistor assemblies, using Fluke resistors — one
ass’y is two 20k managing wire on shellacked mica cards in parallel, and the other is made of eight 5k wire
wounds in sealed green plastic cases in series/parallel. These are not exactly 10k ohms each, but are
about 30ppm (high) for the mica card, and 20ppm (low) for the green plastics, according to my HP 3458A. 

I would like to get them accurately characterized, but never having done this, I don’t know who to have do
it or how much it would cost. Any ideas or suggestions? They can be shipped anywhere cheaply as the box is
small, light, and very durable.

TIA
ed breya | 11 Nov 08:43 2014

Re: HP419A Meter Pegged to Right

If you're talking about washing the board only, I'd say go for it. 
Just run the hottest tap water on it, and a little liquid dishwashing 
detergent, and scrub it thoroughly with an old toothbrush. Then lots 
of rinsing and drying - compressed air can knock out a lot water from 
parts that may trap some.

If any greenish films persist you may want to pour vinegar over it, 
scrub it, then repeat the above process. Just make sure that any 
final washing step is with an alkaline (detergent) - not acidic - material.

If battery juice has worked into the board edge connector, you may 
have to flush it out too.

Ed

At 07:28 PM 11/10/2014, you wrote:
>I'm trying to bring an HP419A back to life.
>
>I managed to replace the corroded nicads with two obsolete power tool 13.2v
>nicad packs. The bucking cell, I swapped for an LR50 alkaline. When fired
>up, the meter pins to the right. Randy Evans posted elsewhere the same
>problem with his 419. Perhaps this is a pattern failure due to the battery
>salts that have invaded the instrument. Anywhere these salts have worked on
>a non-noble metal, the corrosion is permanent. There was a good deal of
>salting on the main amp board connector...easily removed from the gold
>plating with an abrasive eraser. Numerous component lead to solder joint
>areas are corroded, but in no way has the corrosion worked its way to the
>point of opening connections. I can spot faint pools of salts right on the
>FR4. I would like to wash the board in water. I can plastic wrap the pots
>which are all ganged in the upper right of the board, but I'm not sure what
(Continue reading)

Stan Katz | 11 Nov 04:28 2014
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HP419A Meter Pegged to Right

I'm trying to bring an HP419A back to life.

I managed to replace the corroded nicads with two obsolete power tool 13.2v
nicad packs. The bucking cell, I swapped for an LR50 alkaline. When fired
up, the meter pins to the right. Randy Evans posted elsewhere the same
problem with his 419. Perhaps this is a pattern failure due to the battery
salts that have invaded the instrument. Anywhere these salts have worked on
a non-noble metal, the corrosion is permanent. There was a good deal of
salting on the main amp board connector...easily removed from the gold
plating with an abrasive eraser. Numerous component lead to solder joint
areas are corroded, but in no way has the corrosion worked its way to the
point of opening connections. I can spot faint pools of salts right on the
FR4. I would like to wash the board in water. I can plastic wrap the pots
which are all ganged in the upper right of the board, but I'm not sure what
a water wash would do to the composition resistors, and the electrolytics.
Since I'm certain there must be salt all over the board that is invisible,
mechanical removal of visible salts would be an exercise in futility.

Any votes for a water wash? Any better ideas?

BTW the neons are shot. That's another big unknown. My first take is to try
and replace them. I have on order NE-2Us, and NE-83s. These are better for
photoconductor illumination due to having more radioactive Krypton than
NE-2Hs...Very important to fight the Dark Effect. Unfortunately, I suspect
the original neons were probably custom manufactured for HP chopper work.
We'll just have to see....

Stan
Frank Stellmach | 7 Nov 09:03 2014
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Fluke 893 vs 895.........or other?

David,

The calibration of the 332D and of the 5200A requires more than null 
voltmeters only, but that should be clear I assume..

On page 4-4 of the manual from 1972, the 332D calls for a DC Voltage 
Calibration System, Fluke 7101, 7105 or equivalent, including another 
332D, an 845A null voltmeter , 750A reference divider, 720A Kelvin 
Varley, and a Weston standard cell.

Also look for the 335D manual from 1978, which describes the latest 
circuit updates, and has got better schematics..

Check if your 332 already got the FET chopper, the small reference 
including the reference amplifier and a small KLIXON oven, and the 
4-4-2-1 three deck calibrate type sample string already. (D version 
should have that already)

A brief discussion of the instruments versions you may find here:
http://www.eevblog.com/forum/testgear/fluke-332baf-in-the-slaughterhouse/

The 5200A needs an AC/DC transfer standard, including several thermo 
converters.

It's pretty expensive and difficult to collect all these old 
instruments, but maybe it's fun also..

The 3458A on the other hand would replace all these calibration 
instruments to certain limits.. you could completely calibrate the 332D, 
for instance... The 3458A may serve as a Null voltmeter, a reference 
(Continue reading)

David Garrido | 5 Nov 23:13 2014

Re: volt-nuts Digest, Vol 63, Issue 5


So what I am hearing is that I should find either a Fluke 8506 or HP 3458A.................hmmmmmmmm.  I have
always wanted that HP!!!!!

:  )

David
Dan Kemppainen | 5 Nov 20:02 2014

Re: Voltage Reference.

Andreas,

If I proceed down this path, it will be a learning experience. As with
most learning projects, a bit of 'overkill' is usually present.
It's just plain old fun to over engineer something! :)

The LM399 does look like a nice package. Do they all come with the
thermal shield, or is that an option that needs to be purchased separately?

Dan

On 11/5/2014 12:00 PM, volt-nuts-request@... wrote:
> Message: 1
> Date: Tue, 04 Nov 2014 19:20:09 +0100
> From: Andreas Jahn <Andreas_-_Jahn@...>
> To: Discussion of precise voltage measurement <volt-nuts@...>
> Subject: Re: [volt-nuts] Voltage Reference.
> Message-ID: <545918D9.2020105@...>
> Content-Type: text/plain; charset=utf-8; format=flowed
> 
> Hello Dan,
> 
> If you dont need the low noise and long term stability of the LTZ1000 then
> the LM399 will do the job without special resistors (like T.C. less than 
> 5ppm/K).
> 
> The only thing that I recommend is to do a good thermal isolation for 
> the references.
> 
> With best regards
(Continue reading)

Michael Hong via volt-nuts | 4 Nov 21:45 2014

Solartron 7071 Calibration key

One member of the list sent me a copy of 7081 key and it worked like a charm on my 7071!

Michael
David Garrido | 4 Nov 14:46 2014

Fluke 893 vs 895.........or other?

Hello All,

I am in the process of putting together AC/DC voltage standards in the home lab.  I want to add the necessary
equipment to check out the gear and need a differential voltmeter / null detector as called out in the
service manuals for the Fluke 5200A and 332D that I have recently acquired.   I am new enough to this that it
would be helpful for me to have the brain trust here offer a little experience to my thoughts.

The manual for the Fluke 332D stipulates that I need (2) 895A or equivalent.

The Fluke 5200A manual calls for a Fluke 887A and a 931A or equivalent.

And................................... I will be adding a Fluke 5205A to finish off the standards.

There is a very nice 893A at a local shop with ALL factory new accessory cords and a fair price.  Will this fill
the bill or should I be looking specifically for the 895, 887, and 931?

Or................are there any others that are better suited, like the 845A.  Fluke has so many darn
Differential Voltmeters and Null-Detectors that it seems a daunting task to sort it all out.

Cheers,

David

Gmane