Making Resistance Standards Similar to Leeds and Northrop Standards

[Gyro]

That's a comma, not a decimal point isn't it? same in the datasheet. Yes the cheaper 5695 is 1ppm to 400Hz, I don't think we have an image of the winding construction of that one.

Hard to think they would specify single digit Hz to 3 decimal places in the datasheet. It just seems more plausible when you're talking 1592Hz.

[ArdWar]

1592 Hz was (allegedly) from 10000 / 2π, making rad/s values in neat decades.
It is one of the common measuring frequency for artefact metrology alongside the usual 1kHz.

[Overspeed]

Hello

Ok that a comma and not a point so a typical UK/US system

I never use AC so as far that OK for DC /Pulsed DC that OK for me

a xdev webpage with some ( all ? ) Tinsley models

https://xdevs.com/review/tinsleyres/

85 and 95 are no the same , not the same connectors not the same housing ...
Regards
OS

[TimFox]

1592 Hz was (allegedly) from 10000 / 2π, making rad/s values in neat decades.
It is one of the common measuring frequency for artefact metrology alongside the usual 1kHz.

My Wayne-Kerr B221 admittance bridge operates at 1592 Hz for that reason.
An early 1950s model, the manual for which includes a table of reciprocals for those missing their sliderule.
The bridge shows negative capacitance when measuring an inductance:  it is the capacitance that would resonate that inductance at 1592 Hz.

[Victorman222]

What about the kind of wire that the standard is wound with?

For the materials, as i see it, there are two main kinds: the manganin like materials (manganin, constantan) and the nichrome style materials (nichrome, evanohm). The nichrome materials cant be soldered so they don't seem to be very suitable for diy. A shame since evanohm alloys seem to have better TC and temperature range than manganin.

Then choosing between manganin and constantan, it is said that manganin is more susceptible to mechanical stress than constantan, but constantan has a huge thermal EMF with copper of about 40 uV/K. Maybe the TEMF issue could be fixed by having the constantan wires soldered to copper wires at a point that equalizes their temperatures, for example a ceramic chip (like it's done in low TEMF reed relays).

After we chose our wire material, there is the question of what kind of insulation to get. There are three main kinds avilable: bare wire (no insulation), enameled wire, and enameled wire with silk over it. Bare wire seems only suitable for lower resistance values. Enameled wire is good but with smaller diameters like 0.05mm manganin is easy to rip by hand. On the other hand the silk insulation 0.05mm wire is stronger, but there may be a problem with humdity dependence as the silk expands/contracts as described in the NBS circular 470.

Also sometimes there are different anneal? grades, for example with the soviet wires there are: MT MM MС - manganin hard, manganin soft, and manganin stabilized.

It would be very interesting to hear your thoughts. Have you had any experience with the different wire materials and insulation types? Have i misunderstood or missed something important?

[shabaz]

The nichrome materials cant be soldered so they don't seem to be very suitable for diy.

They can be ferruled though : ) Although whether you'd want to do that or not, I have no idea, since once it is done, you'd have to find some alternate way of trimming since it's not a very reversible thing.

Photo shows ferrules on resistance wire (manganin; I didn't try soldering it directly), but this wasn't a resistance standard, it was just intended to be a dummy 4-ohm/8-ohm load which worked for several hundred watts. I didn't notice any change in resistance after subjecting it to that, but again I wasn't looking out for the same performance as a resistance standard so I can't comment on that. I doubt I checked beyond a few digits but I can't recall. For a standard, I imagine you'd want to protect from even faint oxidization, so possibly it wouldn't be good to have bare wire like this in free air. But I'm speculating, I'm not an expert.

[ZGoode]

I wasn't expecting this many responses to my question, lol
These are all great tidbits of information!  Since I already have some basic nichrome on hand, I'm going to try and practice some of the techniques I see here before I try and replicate them using expensive manganin or evanohm wire.  This might be the excuse I have been looking for to buy one of those small jewelry welding torches

[bsdphk]

I read a personal recollection of the history of resistance standards some years back.  (Possibly one of the founders of ESI?)

One of the first thing he mentions is that people thought they had soldered connections, but what they really had was a blob of solder holding a loose wire in proximity with the terminal.

He mentioned point-welding as the solution, and that's certainly inside the DYI perimeter.

[Conrad Hoffman]

A good place to start- https://www.eevblog.com/forum/metrology/manufacturing-custom-high-precision-low-tc-resistors/