Burster resistors

[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]

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?

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

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)

[guido]

He could make some 4W standards with them that directly plug into the front of a DMM.  Make the 2 "sense" banana plugs removable, and then they can also be used to calibrate hand-held meters.

I like this idea, just separate small pcb´s which directly connect into a 4W meter (i have HP3456A with 4W and a Prema 5000 without). If i can get a good solution to make the banana plugs removable (otherwise it won´t fit the Prema). Hand-helds can be done with one pair of connectors hanging in the air. I´ll look into that, it´s put on my to-do list.

Meter was 10 euro´s 

Thanks for the info so far.

[Edwin G. Pettis]

To Zlymex,

I very much doubt that the Fluke 81Meg resistor is wire wound, not that it isn't possible to get a length of wire that long, for the smallest wire size available that is 16,200 feet nominal, the problem being that the largest bobbin size which is 0.500" D x 2.000" long can only hold about 30Meg with the smallest wire.  Not to mention if and that is a big if, a length of wire over 3 miles long could be obtained, the winding time alone would be in hours.  This very fine wire cannot be wound at high speed or you risk breakage.  Unfortunately with the high cost of fine wire, high values of resistance become quite expensive, unless the requirements need the stability and reliability of wire wounds, the cost is often not justified any more.  Even 10Meg resistors are going to cost quite a bit, granted they can be on the order of 1PPM/°C or less with very high stability but it is going to cost you.  With the exception of repairing resistor standards, I generally have not recommended the cost of PWW resistors, I will quote them of course but unless you really need them, you're probably going to say ouch!  Nothing can be done about it per se, the wire manufacturers pretty much price the wire at whatever they think the market will bear.  Despite metal costs coming down dramatically in the last year or two, the price of Evanohm has not come down.  I've had about roughly a 300% price hike in cost over the last decade or so which is something I have no choice but to pass on to customers.

To give you an idea, for that 81Meg resistor, the cost  for 16,200 feet would be around $434.00 and that is just for the wire.

[zlymex]

To Zlymex,

I very much doubt that the Fluke 81Meg resistor is wire wound, not that it isn't possible to get a length of wire that long, for the smallest wire size available that is 16,200 feet nominal, the problem being that the largest bobbin size which is 0.500" D x 2.000" long can only hold about 30Meg with the smallest wire.  Not to mention if and that is a big if, a length of wire over 3 miles long could be obtained, the winding time alone would be in hours.  This very fine wire cannot be wound at high speed or you risk breakage.  Unfortunately with the high cost of fine wire, high values of resistance become quite expensive, unless the requirements need the stability and reliability of wire wounds, the cost is often not justified any more.  Even 10Meg resistors are going to cost quite a bit, granted they can be on the order of 1PPM/°C or less with very high stability but it is going to cost you.  With the exception of repairing resistor standards, I generally have not recommended the cost of PWW resistors, I will quote them of course but unless you really need them, you're probably going to say ouch!  Nothing can be done about it per se, the wire manufacturers pretty much price the wire at whatever they think the market will bear.  Despite metal costs coming down dramatically in the last year or two, the price of Evanohm has not come down.  I've had about roughly a 300% price hike in cost over the last decade or so which is something I have no choice but to pass on to customers.

To give you an idea, for that 81Meg resistor, the cost  for 16,200 feet would be around $434.00 and that is just for the wire.

Thanks Edwin, appreciate very much.
That's true for high value WW. I once tried to order 10 Meg resistors, the manufacturer said they did not do that anymore because they didn't have the thin wires required.
I got some inside photos of an 9 Meg, it seems to me the wire is not much, only a single layer perhaps, wondering how they made it.
I'm very much tempted to teardown my only Fluke 81 Meg resistor although it is a salvaged and rare to find.

[Edwin G. Pettis]

That is certainly an odd looking resistor, for a 9Meg using the smallest wire available 0.0004" diameter, that is about 1800 feet of wire on there.  You can't get any smaller than that and get any kind of length, it is very difficult as is with 0.0004" wire.

For 10Megs, I can get the wire, that is no problem, it's the cost involved.  I can get any size wire I need for that matter but like I said, unless it is for a standard not many people are going to pop for the expense otherwise.

[zlymex]

That is certainly an odd looking resistor, for a 9Meg using the smallest wire available 0.0004" diameter, that is about 1800 feet of wire on there.  You can't get any smaller than that and get any kind of length, it is very difficult as is with 0.0004" wire.

For 10Megs, I can get the wire, that is no problem, it's the cost involved.  I can get any size wire I need for that matter but like I said, unless it is for a standard not many people are going to pop for the expense otherwise.

Thanks again. I have another inside photo of MC brand(?) 5 Meg, Is this from U.K.? do they still make wire wound resistors now days?

[RobK_NL]

MC brand(?) 5 Meg, Is this from U.K.? do they still make wire wound resistors now days?

Mann Components, long since acquired by Vishay (who else?).

https://sites.google.com/site/johnhurll/home/vishay-mann

[zlymex]

MC brand(?) 5 Meg, Is this from U.K.? do they still make wire wound resistors now days?

Mann Components, long since acquired by Vishay (who else?).

https://sites.google.com/site/johnhurll/home/vishay-mann

Thank for that. The MC I was talking about is like photo below, and there is also a VM brand that seems disappeared as well.

[RobK_NL]

They went under the name Vishay-Mann for several years. That would be the VM logo.