My Resistance Standard Box

[lyndonasia]

Hello Everyone,

Years ago, myself and a work colleague were into wood working.  We had a standard joke that the worst possible compliment was the combined compliment / insult.  Upon seeing one of our fine creations someone would remark:

     "Wow, that's really nice!  Did you make it yourself?"

Arrrggghhh!

When I was younger and had very little money and even less patience, many of my completed projects looked just awful.  Terrible looking front panels with felt pen markings for labels and far too many toggle switches!!

I recently got back into electronics and started to do a few projects.  This time around I was determined to make things look a bit more presentable.  Here are a few photos of my precision resistance standard.  I used the "Draw" program in the free software suite called LibreOffice.  (I have been using Linux exclusively for the last 15 years or so.)

There was a bit of a learning curve but I am now able to make a decent looking front panel label much more quickly than before.  I will attach the file for the front label in case you would like to duplicate this project or just play around with the drawing.  The jiffy box was purchased locally in Hong Kong at an electronics shop in Sham Shui Po district.  I printed the label on a laser printer and then laminated it.  I used a piece of double sided adhesive backing cut out from an A4 sheet.  You should be able to find these sheets at your local stationary store.  Here is a photo of the completed project:



I think it looks pretty good and so far... no one has asked me if I made it myself! 

More photos and the label file are attached below.  Please note that I could not upload a file ending in ".odg" so I renamed it with ".odt".  You may very well have to rename the file in order to get it to open properly.  (i.e. resistance standard.odg)

Best Regards,

Lyndon

[Wh1sper]

Looks good!
Thank you for sharing the odt

[Bored@Work]

I am so tempted to ask a particular question ...

[krivx]

Are the resistors soldered or just clamped into the jacks?

[lyndonasia]

@krivx
They are soldered and clamped.

The binding posts had two flat washers.  I bend the tips of the resistor leads carefully in a small arc.  I then soldered each of the leads to one of the washers.  I arranged the two washers so that the soldered lead was sandwiched between the two washers and then put it all together.

My first idea was simply to solder the resistor to the end of the binding post but this method ended up being much better.

Cheers, Lyndon

[lyndonasia]

@Bored@Work

LOL!

Actually, I thought someone would have done so by now!  Anyway... that's a good sign I guess. 

[Sam__]

That's a really nice looking cover.

As an engineer it's easy to forget about the look and usability of a product sometimes.

[lapm]

Now that looks very very nice... Newer tough i could use computer to generate front panels that way. Thanks for the tip..

[CaptnYellowShirt]

Fluke's technical note on this kind of thing says solder is the way to go: Thermal EMF variability < Lead stress stability.

[Vgkid]

Do you mind posting the tech note?

[CaptnYellowShirt]

Do you mind posting the tech note?

"Overall solder (especially low thermal solder) is probably superior to other connection methods, which may have a tendency to result in poor connections over time due to loosening or corrosion."

[iloveelectronics]

Looks fabulous! Glad to know there's another HK residence on the forum!

[acbern]

few comments on this one:
are these low emf binding posts? I do not know this brand, would be interested to know, maybe they are a lower cost alternative to the pomona ones. they should be low emf, to use the 1ppm/0.01% accuracy.
also, any reason why these were not made 4-wire. at the resistances and tolerances used, that would be desirable.

thirdly, does anyone have experience with resistor aging. vishay foil with low aging rates (<1ppm/year) are all oil filled. I built a set of vishay foil standards, using 0,05ppm/k types (at room temperature), but except for the 10k type, i did not use hermetic ones due to cost. so i was wondering if anybody has experience with aging (the non-hermetic ones are said to age/change by about 20ppm over a year, depending on humidity; vishay says that). idea would be conformal coating (after baking) or putting them in a case filled with silicone oil.

what puzzles me is, I spend a lot of money calibrating them, and then they change by as much as 20ppm. I use them for some precision measurements, so 20ppm is pretty high in that respect.

[tszaboo]

They are indeed nice. Do you know which Vishay Foil resistor series is the re-branded Riedon USR?

[acbern]

I'm about to build my own box. Did you do anything to prevent the aging?

Will be using these resistors: http://www.vishaypg.com/docs/63187/zseries.pdf

There is nothing to my knowledge that you can do. Potentially you could insert into oil, but I have not tried. Conformal coating will not help. For stable references the epoxied capacitors are not usable. You need hermetic ones, i.e. oil filled to get below 1ppm/a aging at no load. Wirewound will not do it either (below 1ppm/a)