Mark Sims | 26 Jun 23:00 2016

Thermal EMF of common solder

Several years ago I made my own CdSn solder...  I had access to a proper chem lab with fume hoods, etc.   And no,  I
can't supply any and won't be making any more. 		 	   		  

Keithley 2001 - do you need to open it to calibrate it?

I got the 2001 that I ordered yesterday. There are a few things that make
me feel uneasy about it, so I will probably return it.

The calibration seal is missing off the front, which is obvious from the
eBay photo, but also one at the bottom which looks as though one needs to
open in order to get inside the unit. That had a seal, but has been broken.
I'm wondering if that would be a normal part of the calibration routine, or
if someone has opened this up after it was calibrated.

The cal was due "Jan/12/10", which I assume means the 12th of January 2010.

Also, although when I see the pictures on eBay I never noticed it, a closer
inspection of the photos .

does show that the hole on the front where a calibration seal would be
placed, has at one time in the past had a device too large pushed into the
hole. The hole is no longer round as I would expect it to be.
Andrea Baldoni | 26 Jun 16:12 2016

Thermal EMF of common solder

Hello All.

I measured the thermal EMF of two common solder, the lead free
Sn96.5/Ag3/Cu0.5 and the old Sn60/Pb40.
I have ordered a spool of Sn96/Ag4 (the recommended low-thermal-EMF replacement
for cadmium based one) and I will post the result for this too.
I could probably find also Sn97/Ag3 and Sn97/Cu3 if it's reasonable to check
them; I accept suggestion on what else to try between the RoHS complaint ones.

Copper - Sn96.5/Ag3/Cu0.5 -> 3.4uV^C
Copper - Sn60/Pb40 -> 3.3uV^C

Best regards,
 Andrea Baldoni
Russ Ramirez | 24 Jun 18:59 2016

Keithley 2182A

Just wondering if any of you might have a PDF of the subject Nanovoltmeter?

Illya Tsemenko | 24 Jun 18:38 2016

Re: Keithley 2001 vs HP 3457A multimeters / Any problems to watch out for on Keithley 2001? (Todd Micallef)

Aha! :)

Hi David,

First few sour points to make sure you got what to expect.
* 520$USD is bit steep for 2001 from 90's you got, and VFD seem to be 
fairly faded according to auction pics.
* It may be still have issues internally, even though showing reading 
does not reveal anything in first glance.

2001's are fairly capable DMMs and I personally dealt with no less than 
7pcs of them over last years. Currently I still own four units of same 
age as your win (judge from S/N). While they are worse than 2002/3458 in 
terms of stability/noise, I would not trade my 2001's to fancy 
3446X/34470 meters.

Also 2001 support scan-card addons so you can easily expand DMM with 
scanner function, or even nanovolt-preamp if you dedicated enough. I'm 
working on nanovolt support with 2001, but that's long story. Some 
details with DIY card I covered here:

To get you ready:

1). It's bit tricky to setup and need little bit of time to get familiar 
with, but otherwise on par with modern 34470/DMM7510 with bit worse 
resistance/current specs. No RS232, so bit more expenses to come for 
GPIB interfacing if you don't have that already.
As Todd pointed out already to my repair article, some bits of info are 
linked there, as well as firmwares and documentation.
Here's example test log with reading 1mV DC voltage with three meters : 
(Continue reading)


Keithley 2001 vs HP 3457A multimeters / Any problems to watch out for on Keithley 2001?

I've got an HP 3457A (6.5 digit multimeter) which has served me well.  But
I see a Keithley 2001 7.5 digit meter on eBay

which sort of tempted me as

1) It has an extra digit, I have not looked to see how much that extra
digit gains one. It would be nice to think the uncertainty is only 10% of
the 6.5 digit 3457A, but I very much doubt that's the case. I have not
looked at the specs closely.

2) I see it was a current model at Farnell selling at £4150 + 20% VAT =
£4980, so quite a bit of money. The 2001 is not a cheap meter.

3) It was £650 or "best offer".

4) The 3457A is a great meter, but is much older.

Anyway, my offer of £380 (GBP), was accepted, which is 7.6% of the current
cost of this new from Farnell. As I write, this is around $520 (USD), but
with the UK just voted to exit the EU, and the pound fallen quite a bit,
that US price may not be very representative. But it seems fairly cheap. I
can't see any Keithley 2001's sell for that low on eBay, unless they have
had faults.

Having made an offer, it been accepted, and me paid for it, now I decide to
see if it was a good or bad idea! I think one is compare the meters first,
then make a decision to buy or not, but I have done this the other way
(Continue reading)

David C. Partridge | 13 Jun 18:32 2016

New scan of Solartron 7081 Service Manual is now available.

I just uploaded a new scan of the Solartron 7081 Service Manual. It is
scanned DUPLEX including schematics.  It has been extensively cleaned up and
combines data from the final revision of the manual plus selected
information from other sources.

Most of the document is A4 portrait, while the schematics are A3 landscape.
This scan has had numerous annotations and corrections made, particularly
errors in the schematics.

The AC Linearity Modification details are included on the AC RMS Converter

Schematics for both the 2564 version (board 70817504) and 2764 version
(board 70817514) are included.


The whole document with the exception of the schematics has been OCRed.


Lou Amadio | 6 Jun 03:51 2016

Replace neons with LEDs in Fluke 845AB

Question for Dallas Smith:

I want to replace neons with LEDs in my Fluke 845AB.

Following your instructions below, did you mount the LEDs where the neons
were on the PCB and use the plastic light tubes or did you mount the LEDs
hard up against the LDRs in the yellow foam block?

Thanks, Lou


Dallas Smith, 2 years ago

Permalink <>

Raw Message


“Finally got around to modify my Fluke 845ab with LED 's for the chopper
circuit. Used the 17 volt windings for LED's (Mouser
941-C513AMSNCW0Y0511 Warm White Round LED) instead of the 130 volt, move
red wire on transformer pin 9 to pin 7.This winding is 180 degrees out
of phase, so I reversed the steering diodes (CR106 & CR107) I left in to
help make sure the phase was correct for the LED's when connecting.
Change R154 to 6K to set the brightness, selected for good operation of
the zero control. Then install jumper to replace C119. Also changed the
filter integration response caps C111 to .022uF and C116 to 47uF, this
stabilized the jitter to a manageable mode of operation. Meter now works
(Continue reading)

Frank Stellmach | 5 Jun 14:20 2016

LTZ1000 project build

This whole discussion does not really apply to the LTZ1000 circuit, that 
is the bare 7.15..V output, w/o step up amplifier, as all drift 
parameters were attenuated by orders of magnitude, depending on the 
resistors, R1-R5.

In the eevblog thread, several volt-nuts measured the real dependency, 
in contrast to the datsheet, which simply claims 1:100 attenuation for 
each of these resistors:

R1 	R2 	R3 	R4 	R5 	author
120 	70000 	70000 	12-15k 	1k 	
-1/770 	-1/250 	-1/1400 	+1/100 	
-1/600 	-1/238 	-1/1000 	+1/87 	
1/714 	1/250 	1/3333 	1/105 	
-1/670 	-1/238 	-1/1184 	+1/74 	-1/75 	Andreas

Therefore, even humidity effects at most affect R4/R5, with 1/75 impact.

I also think, that it's possible for volt-nuts to measure such residual 
effects, by assembling several references, keeping the parameter of 
question (e.g. humidity or temperature) constant for the master 
reference, varying this paramater for a DUT, and evaluating the drift by 
(Continue reading)

Lars Walenius | 3 Jun 18:01 2016

Re: LTZ1000 project build


Do you have any idea of the aging and humidity sensitivity of these 2ppm/C resistors?

I have tested many resistors during the years and my opinion is that tempco is not the biggest problem for
normal nuts use but of course may be if you sell a product. For a nut it is quite easy to check the tempco but not
aging and humidity sensitivity.

Of the resistors I have tested it is only hermetical sealed resistors that I don´t see a humidity
sensitivity on. Even if they are bulk metal foil, wire wounds or metal films with low tempco´s they seem to
have very varying humidity sensitivity if not sealed. Lower values of resistance (100-1k) normally
seems to be better than 10-100kohm values that in all families may have up to 1-2ppm/%RH.
Last year I bought wire wounds, to be used in a LTZ1000 based design, that were supposed to be insensitive to
humidity but they were not. They were even worse than other brands of WW and had several months of time
constant. After a while the manufacturer admitted that it was a problem in the manufacturing and they were
humidity sensitive. So far I haven´t received a replacement.

Of course if you have a resistor with 2ppm/%RH and a seasonal variation of 50%RH it is only maximum 1ppm
seasonal variation on the output on the LTZ. That is not easy to measure for most of us nuts.


Från: ian@...<mailto:ian@...>
Skickat: den 26 maj 2016 13:35
illya@...<mailto:illya@...>; volt-nuts@...<mailto:volt-nuts@...>
Ämne: Re: [volt-nuts] LTZ1000 project build

Hi all,

(Continue reading)

Frank Stellmach | 27 May 11:28 2016

LTZ1000 project build


I monitor two DIY LTZ1000 references, standard circuit from LT 
datasheet, since about 7 years.

These are running on 45°C, and are using 5 precision wirewound resistors 
(PWW), T.C. ~0.2 .. 4ppm/K.
BOM cost are currently 42.85$ for the LTZ1000 (non A!!) directly from LT 
(recommended, beware of chinese fakes), and about 7-10$ for each resistor.
So each reference may be built for about 100$ in total.

By avoiding some pitfalls, like excessive heating, causing hysteresis 
effects, these reference will have an annual stability of typ. 
-0.8ppm/year, without any special treatment, like "ageing", slots in the 
PCB, or usage of extremely sophisticated and expensive metal foil resistors.
One only has to monitor the drift of each reference if it's having this 
typical drift rate, or not.

Andreas Jahn currently makes a great job in investigating on the overall 
T.C. performance of his LTZ references, in terms of selecting these PWW 
resistors, trimming by 400k resistor, and LTZ lead length.

I'm doing that drift monitoring by comparison of a total of 4 
references, that's an additional LTZ1000A in a 3458A, pimped to 65°C, 
and not running continuously (practically no drift), and two stacked 
SZA263 in a Fluke 5442A, which have typ. +1ppm/yr, but this instrument 
also is not powered continuously.

The differences within this group are still within +1/-2ppm after 7 years.

(Continue reading)