Electronics > Metrology

Burster resistors

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guido:

Bought a Burster Digivar recently at the big national ham market for cheap. Seventies stuff, a bit of crusty inside. No info on the net and it seemed to be a multimeter of some sort. Some display driver seemed broken.



So i took it apart. Inside was a generic voltmeter module (nothing special), which contained some panaplex displays. Nice.
But also this came out:



A number of precision resistors from Burster. Type BP 2T from '76 to '78. A nice range: 1, 10, 100, 1k, 10k and 100k on the left (1 ohm is 0.05%, 10 is 0.02% and the others 0.01%). On the right some other values, a few 2k. They measure fine (two zero's after the decimal point with my 'not so' calibrated meters). Only the 198k seems off (could be the meters).

Plan is to put them in a box as 'resistance standard' and to have them checked. Then i can use them to calibrate my own meters.
Just a box with a number of connectors to connect them individually. Also have a 1M precision resistor to add.

Which resistor values require 4 terminals? 1 and 10 Ohms?
And does anyone know these puppies?

zlymex:
I suggest to use 4 terminal at least for 1, 10 and 100, better for 1k as well. I use 4 terminal for up to 100k but not for 1M.
A 4 terminal resistor can be used as 2 terminal but not the other way round.

zlymex:
Hi DiligentMinds.com,
Perhaps a little off topic to ask, but do you know what kind of wire Fluke used in their 81 Meg resistors in 5450A?
https://www.eevblog.com/forum/blog/eevblog-544-fluke-5450a-resistance-calibrator-teardown/75/
It's WW isn't it? I calculated again that even they use 0.0005 Evanohm, the length will be over 4 miles. Could that be done in reality or they use even thinner wire?

zlymex:

--- Quote from: DiligentMinds.com on March 29, 2016, 04:32:27 am ---
--- Quote from: zlymex on March 29, 2016, 02:38:22 am ---Hi DiligentMinds.com,
Perhaps a little off topic to ask, but do you know what kind of wire Fluke used in their 81 Meg resistors in 5450A?
https://www.eevblog.com/forum/blog/eevblog-544-fluke-5450a-resistance-calibrator-teardown/75/
It's WW isn't it? I calculated again that even they use 0.0005 Evanohm, the length will be over 4 miles. Could that be done in reality or they use even thinner wire?

--- End quote ---

Yes, it very well could be Evanohm, but the 100M value does not have to be that stable, so they may actually be some other technology inside the metal hermetic package [like metal oxide for example].

You can get Evanohm in even smaller diameters, but it is VERY expensive; and very easy to break while winding or welding.  Not something for the faint of heart to try...

I think if I were to try to make a high-value resistor, I would start with the LTC series from 3RLab [in Korea].  These are +/-2ppm/K, and come in high values up to 200M.  You only need one resistor for a 100M standard, and 5 of these resistors in series would make a 1G resistor.  Get some borosilicate ["Pyrex" brand] tubing, and some Dumet wire.  Weld the Dumet wire to each end of the resistor, and seal the resistor inside of the glass tubing using some PTFE spacers to keep it centered.  The Dumet wire matches the TC of the glass, so will make a good, lasting seal.  Evacuate [or fill with Argon] the glass tubing before sealing it with a MAPP gas torch.  Now you have a high-value resistor with good TCR, and because it is hermetically sealed it should have good time stability.  Maybe not as good as Evanohm, but if you calibrate it before each use, then it is "Good Enough" to calibrate a DMM.

See:  http://www.3RLab.com

--- End quote ---
Thanks for these info, very helpful indeed. I'll open another thread.

quarks:
here is a picture of my BURSTER Type 115 with 0.004% and around 1ppm/°C (unfortunately no longer available)

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