Many years ago, there was an article (in Popular Electronics?) that needed a
very high value resistor. They built it by drawing a line between two
terminals with Higgins India Ink. No idea if the ink is still made the way it
was 50 years ago...
> So how does one make ones
The 3M model 703 static electric field measurement gun can measure the
magnitude and polarity of a static field.They use a 200 millicurie tritium
source and a high resistance circuit to do the measurement. The tritium
source is used as an ionization source. It runs off of two 9V
Oops... should have said 0.8 mm and not 1 mm.
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I got in my latest PCB based shorting straps for test equipment banana jacks
from OSHPARK. You can find them here:
http://www.eevblog.com/forum/metrology/copper-binding-post-shorting-straps-for-low-thermal-emf-alloytempering/msg1389056/#msg1389056
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Mine have 2 oz copper on each side and some via stitching between the sides.
I am waiting for the prototypes from OSHPARK to determine if / where I can add
additional vias without compromising the structural integrity by creating
"break me here" fault paths.
I have a 4-way layout in the
If the two wire straps work out, I will probably do a four wire short. When I
need I four wire short (which isn't very often), I usually just use a freshly
stripped piece of copper wire.
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It's basically an "E" shaped PCB around 15x35mm that can be used to do things
like short between sense and drive banana jacks.
-
> I'm trying to imagine what you are describing - is this PCBs with 4mm banana
> plugs installed or a small PCB with two slots at 3/4" centres to match
The main use of these would be shorting sense to drive jacks. They could also
be used for input shorts. The advantage over bare copper would be the ENIG
gold finish... bare copper quickly forms oxide layers and copper oxide has a
horrible thermal EMF. Granted, ENIG gold basically involves
Recently on EEVBLOG there was a thread where a guy mentioned that he was going
to machine some shorting bars for banana jack out of copper. I made the
suggestion to gold plate them to avoid copper oxide issue. Another guy
mentioned making them like a PCB (like Fluke does).
I did a little
I think you may be paying to much... check out the pricing at gojgo.com
They do excellent work for very low prices. Also check how the price varies
with quantity. Often you can get 5X the number of boards for a 20% increase
in total price (excluding shipping).
>
I used to make button / keytops by making a mold of a compatible one in clay or
silicone rubber and filling it with epoxy followed by a lot of fiddly work
carving out the interface to the keyswitch plunger.
These days 3D printers are your (frustrating) plastic pal who's fun to be with.
Not always.. A guy I worked with was pulling a ceramic 40 pin dip out of a
socket when it broke... sliced his finger to the bone. There was initially
some concern that it was a BeO ceramic. Checking with the manufacturer showed
it was not. I checked the socket afterwards, and it seemed
Once you get past 99.99% purity funny things begin to happen... I have some
100% pure Cu oxygen free cable (says so right on the jacket) made in China that
is magnetic! You can't do that with the cheap stuff, now can you? ;-) Oh,
and it is so pure that it has three times the resistance of
When making the CdSn solder you want to avoid contamination with other metals.
It doesn't require much contamination to lose its magic foo powers. So no
metallic molds or tools used.
And what, no shaved cadmium with a Bordeaux garlic reduction? Try it, it's
delicious ;-)
I don't know if it the proper way but I used a very nice fume hood. Measured
the metals (high purity), melted them in a quartz crucible, stirred with a
quartz rod, and cast it in a ceramic block with a spiral pattern machined into
it with a ball mill. You don't want to contaminate the
A few years back I whipped up a batch of Cd/Sn solder... but I had access to
the proper equipment to do it safely. And no, you can't have any!
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Yep, a single 8-pin chip with 4 pins used (VCC, GND, in, out). I did
something very similar to this in an ATTINY-13 (OK I used a TINY85, but the
code was less than 200 bytes long). I can't share it since somebody paid for
the thing and it is not directly applicable, but it is rather
At one time I came across a Russian company that was selling JJA's based on
high-temperature superconductors (liquid nitrogen cooled). They had both JJA
chips and complete systems. They were not quite as good as the helium cooled
devices but were quite a bit cheaper and easier to work with.
Most NiMH cells have a capacity of around twice what a NiCad has, so a NiCad
charger that works at a C/10 charge rate will be charging NiMH cells at C/20.
That can be an acceptable trickle rate for NiMH cells, but I prefer something
in the C/40 neighborhood. I put some in an electric shaver
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.
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Mark's Law of Rubidium Goodness... the bigger the box, the better it is. The
HP5065A is one of the best units ever made. It can rival a cesium beam unit.
The X72 is a horrid little creature.
I would also go with the M100 / FRK units. The LPRO an FE56xx units were
designed for telecom use
I stopped by my favorite electronics store to buy some more Oldaker meter
probes. Alas, I was told that Oldaker had a fire and is no longer in
business. They were a small (7 person), family owned business that made
really nice and affordable test leads. Apparently they don't plan on
Egad, I just read through that EEVBLOG thread... now I need a mind enema...
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Maybe a Tektronix AM502 module and the single slot TM501 mainframe?
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It's a lot harder than making stable capacitors... particularly for low
inductance values. I think the process involves the use of rainbow flavored
unicorn tears. There are some 0.01% standard inductors on Ebay starting at
around $400 each. Also some .1% ones for a lot less. Decent L
One thing to watch out for on the 5450A is burned out segments in the
14-segment LED displays. The display chip they used is rather weird (each 14
segment digit is actually two 7-segment displays mixed together) and VERY
unobtainium. Mine has a missing segment on one of the digits and I have
Think twice about those Vishay metal film resistors... they have known
stability problems (particularly concerning humidity). Also they can have
problems meeting their own specs. There is an active thread of eevblog.com
concerning the issue. Consensus seems to be precision wire wound
Probably a wonkey electrolytic cap... In the old TV days, this was usually
caused by a coupling capacitor, not a filter capacitor.
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Most low-end 3D filament printers can print in either PLA, ABS, or even
nylon. PLA prints are known to distort in a hot car. ABS is extruded at
around 250C. I think nylon is a bit higher. I would think that ABS would
work well.There are now some low-ish cost (like under $3000)
John Miles has included my HP-3458A cal ram data dumper program in the latest
release of his excellent GPIB Toolkit package. You can download it from the
KE5FX web site. The released version produces the formatted listing of the
various cal RAM values in its output (it is the same version
Using Legos!
http://arxiv.org/pdf/1412.1699v2.pdf
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Another program that is supposed to be very nice is DIPTRACE. Their free
version is limited by pin count... Eagle's free version is limited by board
size. Eagle has more community support than the other packages.
I have uploaded a .ZIP file with the source code and Windows .EXE file for the
calibration/data memory data dumper program here:
http://s000.tinyupload.com/index.php?file_id=0219779600667150
This output of this version of the program also produces a formatted/commented
listing of what the
Yes, the program requires GPIBKIT. Copy the code to the GPIBKIT directory.
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It's only for the 3458A.
Unless you want to play with the code, you only need the pre-compiled .EXE in
your GPIBKIT directoty.
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Eagle has a freeware version that is for non-commercial projects of smaller
physical size. It is a very stable program... it has never crashed on me.
Eagle has LOTS of community support.
All the PCB services that I mentioned can fab boards directly from Eagle .BRD
files so you don't even
Another package that has a good reputation and is fairly inexpensive is
DIPTRACE. It is supposed to be easier to learn than most packages. Their size
limits are based upon pin count, not board size. Their non-commercial free
version is limited to 500 pins/2 layers. A local university
OSHPARK.COM is in the US and will do three boards for $5/sq inch... with no
setup or shipping charges.
For larger boards or quantities dirtypcbs.com and gojgo.com make nice boards
for dirt cheap (particularly for boards under 5x5 or 10x10 cm). They can be
1/10th the cost of OSHPARK.
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...
Yes, I have laid out a pair of boards that has the battery module circuits on
them. One board plugs into the mainframe (it has the thermistors on it) and
the other has the rest of the circuitry. I have not ordered them yet... I
need to buy the festoon lamp connector and have been waiting
I suspect that 90% of the work could be done with a single kit. That will get
one card out of the chassis. But, there are always those annoying problems
where getting two cards out can make life a little easier. With two kits you
could also hack up the extra 44-pin board to make a smaller
The TM500/5000 and HP5370 extender kits are now available (actually they were
ready a few weeks ago, but I was going to be out of town and did not want to
leave people hanging).Prices are:HP5370 extender card kit - has 2 x 36 pin
extenders and 1 x 44 pin extender. $30 setTektronix TM500/TM5000
The tightest clearances are where an etch runs between two pin on the ribbon
cable connector. The connector pin are spaced 0.10 apart. The pads are .060
octagonal pads so edge-to-edge is a .04 gap. A .016 trace runs in that gap.
So there is a .012 clearance between the pad edge and trace.
I tried to send you a copy of my program, but the email bounced...
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BTW, you can get LEDs that are designed specifically for flash applications.
They can handle high peak currents, have decent color spectra, and/or fast
rise/fall times. There are also LED driver chips made for flash applications.
I would probably use green or yellow LEDs, but the white ones should not be a
problem.
I built an LED analyzer/integrating sphere and one of the features is a
circuit that optically measures the LED driver PWM frequency. It can also
detect the minute variance in LED intensity from an LED
No web page, but a little description here. It has changed quite a bit from
the original description. Now uses TAOS color sensors. Suppors Melexis IR
thermometer chips. Has 16 bit A/Ds. Processor is an ATMEGA 1284. The control
program is based on Lady Heather. Besides LEDs it can
5200A extender cables are a go! Connectors and boards are on order (from a
different board fab in Hong Kong this time). One board goes on each end of the
extender. Boards are connected by a 50 pin and 40 pin ribbon cable.
Those are not holes... they are polarity markers on the silkscreen for the
connectors.
I do have one concern about doing the extender with ribbon cable. It is rated
for 300V and three of the card slots do have 300V on them.
I have a 732A that is missing its battery module. Does anybody have or know of
a source for a replacement?
Also, would there be any interest in a replacement circuit assembly for the
battery module? It would probably consist of a small board that plugs into the
2x6 pin edge connector and
I thought about a lithium pack, but that would probably require a new power
supply board or extensive mods to the current one. The charging system for
lead-acid batteries and lithium batteries is quite a bit different. Not sure
what it would take to reliably/safely cobble a lithium
I'm porting over my HP3458A NVRAM data dumper program to use John Miles GPIBKIT
routines. It should make it usable with most GPIB interfaces out there and be
able to run under more modern versions of Windoze.
My first crack at it is working, but it is quite a bit slower than my original
I have the GPIBKIT version of my HP3458A cal ram data dumper program available.
If you want to try a copy shoot me an email. If it works out, I'll see if
John wants to include it in the standard toolkit distribution.
You will need to download GPIB tool kit from the KE5FX.COM web site, run
The program outputs a 2kB (or 2 x 32kB) binary ROM image files files along with
a couple of ASCII format files of the data. 2kb for CAL ram and 32kb for DATA
ram (probably not needed, but it can dump the data RAM chips). The binary
files have the extension .hi and .lo (CAL ram data is only
You REALLY don't want to mess with that 24 pin NVRAM chip... it contains the
calibration memory. If you bugger the data in it, you get to spend a couple
of grand getting the meter back into working order. I know a couple of people
that did just that.
The solution is to first make a backup
The problem with removing the chip and copying it is the very real chance of
glitching the contents in the process. Much better to make a backup copy first.
The 32Kx8 NVRAMS are used for system memory and things like storage of user
programs and data.
Note that the two 32Kx8 devices are form
Why risk having to re-cal the meter? There are several GPIB-232CV's on Ebay
right now... Two of them are under $60 Buy-It-Now... cheap enough to be
worth trying. The Prologix USB converter is around $100... $150 new from the
factory.
I recently bought a couple of these gizmos: ($19 bucks a pop)
http://www.ebay.com/itm/261527017059?ru=http://www.ebay.com/sch/i.html?%3Cem%3Efrom%3DR40%26_sacat%3D0%26_nkw%3D261527017059%26_rdc%3D1
Stick in a semiconductor/r/l/c/etc, press the button, and it tells you what
it is, the
The HP3458A MREAD command returns a 16 bit value as a decimal integer. The 2kB
cal SRAM is only 8 bits wide and the values are returned in the high byte. On
two of my machines the low byte is always B9 hex. One the other one (earlier
serial number) it is always FF.
I did some more playing around with the 3458A memory dumper this weekend. I
built up another system using a different computer/cables/software/GPIB
interface (one I built using an AVR chip that emulates the Prologix RS-232/USB
converter). I noticed than a couple of dumps of the CAL ram
I got in my prototype extender cable boards from OSHPARK.COM today. OSHPARK
only builds boards in multiples of 3 and I only ordered three boards so could
only build one cable. It seems to work very well. I tested it with several
different TM500 and TM5000 modules (using another set of cables
I have three HP3458A's and decided it was time to back up the battery backed
static RAM chips. I wrote a program to dump the RAM contents over the GPIB bus
using the undocumented MREAD command as documented by Poul-Henning. I dumped
both the 2kB CAL rams and the 32kW auxiliary data RAMs
A few people have asked what the extender board looks like. Attached is a
rendering of the board. The same board is used on each end of the cable. One
of the boards would have the edge connector soldered to the top, the other
plugs into the mainframe. Two 39 or 40 pin ribbon cables connect
I am looking for some (well at least one) DL02614 dual character 14 segment
common cathode LED display modules. These were used in the Fluke 5450A
resistance calibrator. They were made by Litronix and maybe Siemens.
Yeah, and it's a weirdo too. Each digit is built as two seven-segment
displays, so there are two cathode lines and 7 anode lines per char. All the
current 7 seg displays have 14 anode lines per char.
I've thought of doing a replacement front panel board (probably using a micro
and LCD
Is one used as an exponent, and doesn't need all segments to work?
Nope... no joy there...
The missing segment is the top segment of one of the digits.
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Valhalla is still around.. I've purchased manuals from them (a bit pricey,
low quality repros). Email or call them and ask. But on a couple of their
products they have disavowed all knowledge of their existence...
Some Russian company has a JJ standard that uses high-temp superconductors and
liquid nitrogen cooling. Because of things like grain boundary issues in the
HTS, it is not quite as good as a 4K cooled unit.
-
Of course at the
present time given the fact that the JJ has to be
One problem with leaving the 3458A on all the time is the vacuum fluorescent
display. These have a rather limited lifetime and leaving them on 24/7 puts a
lot of hours on the tube. Someday those displays will become unobtainium...
Take a close look at the photos of Malones nice little voltage reference boards
(http://www.voltagestandard.com/Home_Page_JO2U.html). The voltage reference
chip is mounted on an isolated peninsula of PC board material to help isolate
it from stress due to environmental changes.
A common fault with these is the Mostek CPU/peripheral chips on the
motherboard. The pins corrode away.
Another common fault is with the video monitor. I had one where the socket on
the CRT was bad... intermittent connection to the filament. Another blew a
couple of transistors. Also the
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