Author Topic: ESI Resistance Standard SR1010 and Standard Resistor SR104  (Read 22734 times)

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Offline BradC

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #50 on: September 30, 2019, 03:35:28 am »
Yes, and nowadays it's quite simple to supervise humidity using integrated sensors. Since i have a lot of desiccant in that SR1010, i won't touch it any more, but observe humidity inside.
[..]
  If you don't intend to replace the "consumed" (or "spoiled") desiccant, but just observe the internal humidity, why use a non-zero amount of desiccant in the first place?

The dessicant isn't there to remove humidity, it's there to buffer it.
 
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Offline dietert1

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #51 on: October 02, 2019, 04:47:17 am »
Slowly i am coming to grip with our SR1010-1K and here is an example measurement. This is a resistance bridge with a voltage divider 10 V to 3.3 V (3x 1 KOhm) and one 1KOhm resistor serving as a 6.7 mA current source to the DUT, which is an Alpha Electronics HCZ500R00 (Vishay hermetic foil). The DUT has been in a 40 °C oven for about a week. Bridge is driven by our Geller reference.
I logged the bridge voltage difference and the temperature of the dry and boxed SR1010 with our two HP 3456A. During the night the SR1010 temperature was following the decreasing room temperature for about 5 hours. Vertical axis is 1 ppm, horizontal is 0.5 K. Red line is a calculated filter, green a line fit.
Now i can correct the SR1010 temperature dependence numerically (linear -1,84 ppm/K)

Regards, Dieter
 

Offline dietert1

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #52 on: November 04, 2019, 08:32:21 am »
After i got about 10 uV of thermal EMF by heating a copper lug between fingers, i checked the materials used in a SR1010. I think the binding posts are gold-plated steel as well as the nuts on them (front and back). The trapezoidal plates inside appear to be copper. This construction is prone to generate thermal EMF. The other SR1010 i am operating in a box, well protected from air movement, generates about 300 nV.
Pomona 3770 copper binding posts fit, but their diameter in the back is about M4 and the holes in the plates are more like M6. And the Pomona posts come with steel nuts. So one needs to buy copper nuts and washers in addition.

Regards, Dieter
 

Offline splin

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #53 on: November 04, 2019, 05:40:07 pm »
After i got about 10 uV of thermal EMF by heating a copper lug between fingers, i checked the materials used in a SR1010. I think the binding posts are gold-plated steel as well as the nuts on them (front and back). The trapezoidal plates inside appear to be copper. This construction is prone to generate thermal EMF.

I'm having a very hard time believing that ESI would have used gold plated steel - these aren't cheap items. Have you checked with a magnet? Could someone have replaced them before they came into your possession?
 

Offline dietert1

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #54 on: November 04, 2019, 08:44:41 pm »
Of course i can't guarantee the binding posts are original, but the web is full of images of SR1010 and they look like original. And they are identical on the two SR1010 we got from two different sources.
I just checked it, the binding posts and nuts are non magnetic. They don't have the reddish shine of copper nor the golden color of brass inside, but appear white. Maybe silver? I'd prefer copper, since i am using copper lugs and copper cables.

Best regards, Dieter
 

Offline Edwin G. Pettis

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #55 on: November 04, 2019, 11:54:58 pm »
The normal material for ESI terminals is Tellurium Copper, it is a dull golden color usually, depends on the alloy's mix.
 

Online Kosmic

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #56 on: November 05, 2019, 01:43:59 am »
Personally I would not replace the binding post with Pomonas.

What protocol and instruments (meter / cable / connectors) are you using to measure the thermal EMF ?
« Last Edit: November 05, 2019, 04:37:49 am by Kosmic »
 

Offline dietert1

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #57 on: November 05, 2019, 07:58:50 am »
I am not really measuring thermal EMF, since it's a dirt effect and i think it will be negligible  once i have the correct materials. A simple test i always do is: Connect one of the resistors with four copper lugs and copper wires to the HP3456A input (input terminals are made of copper). After a minute or two i get a zero reading of -0,6 uV. This is "without" thermal EMF. Then i heat one of the lugs on the SR1010 terminal between my fingers, so there will be a 5 or 10 °C temperature increase. The HP 3456A reading slowly creeps up to about 10 uV and it slowly returns back to -0,6 uV as soon as i take my hand off. This may take two or three minutes. I can repeat that on the other terminal giving -10 uV.

The binding posts are certainly not copper, they look white inside like steel or silver. I guess the SR1010 is from a time when users were satisfied with 1 or 2 ppm results, which are easy to get if you keep the lab at 23 °C and don't touch the setup. In my current bridge experiment i have 3.3 V across the DUT and see a 0.3 ppm difference on voltage reversal, so thermals appear at a 1 uV level.

Regards, Dieter

 

Online Kosmic

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #58 on: November 05, 2019, 03:01:37 pm »
I am not really measuring thermal EMF, since it's a dirt effect and i think it will be negligible  once i have the correct materials. A simple test i always do is: Connect one of the resistors with four copper lugs and copper wires to the HP3456A input (input terminals are made of copper). After a minute or two i get a zero reading of -0,6 uV. This is "without" thermal EMF. Then i heat one of the lugs on the SR1010 terminal between my fingers, so there will be a 5 or 10 °C temperature increase. The HP 3456A reading slowly creeps up to about 10 uV and it slowly returns back to -0,6 uV as soon as i take my hand off. This may take two or three minutes. I can repeat that on the other terminal giving -10 uV.

Interesting, I will try to repro with my SR1010.

The binding posts are certainly not copper, they look white inside like steel or silver. I guess the SR1010 is from a time when users were satisfied with 1 or 2 ppm results, which are easy to get if you keep the lab at 23 °C and don't touch the setup. In my current bridge experiment i have 3.3 V across the DUT and see a 0.3 ppm difference on voltage reversal, so thermals appear at a 1 uV level.

In the manual of the SR1010, ESI don't specifically talk about the binding post but they explain in details how the resistor were made and how they selected materials that create low EMF when coupled to copper. I would be surprise if in the end they decided to use cheap steel binding post.

Technically IET still sell binding post similar to the one used back in the days by ESI. Like Edwin mentioned, they are made of tellurium copper.

https://www.ietlabs.com/binding-posts-bp-1000.html

It's also important to note that Tellurium Copper is more silver/white than red.
« Last Edit: November 05, 2019, 03:07:30 pm by Kosmic »
 

Offline dietert1

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #59 on: November 05, 2019, 05:10:57 pm »
The binding posts in our SR1010s look different. They have two different isolators (different shape and different color). The outside isolator looks dark brown and fits into the hole. The inside isolator looks like teflon and has a larger conical hole covering up the other isolators end.

By the way, the tellurium copper of the Pomona 3770 body material appears reddish, similar to the trapezoidal sheets inside the SR1010. If something looks white, probably it has little copper. Even brass doesn't look white. I know this can't replace a chemical analysis.

Meanwhile i ordered copper screws to test whether they work better and will report later.

Regards, Dieter
 

Offline MegaVolt

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #60 on: November 06, 2019, 09:01:41 am »
I checked my SR1010 100 kOhm with a magnet. If it is not disassembled, then the magnet has nothing to be attached to.
 

Online Kosmic

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #61 on: November 06, 2019, 02:45:02 pm »
I am not really measuring thermal EMF, since it's a dirt effect and i think it will be negligible  once i have the correct materials. A simple test i always do is: Connect one of the resistors with four copper lugs and copper wires to the HP3456A input (input terminals are made of copper). After a minute or two i get a zero reading of -0,6 uV. This is "without" thermal EMF. Then i heat one of the lugs on the SR1010 terminal between my fingers, so there will be a 5 or 10 °C temperature increase. The HP 3456A reading slowly creeps up to about 10 uV and it slowly returns back to -0,6 uV as soon as i take my hand off. This may take two or three minutes. I can repeat that on the other terminal giving -10 uV.

Interesting, I will try to repro with my SR1010.

So I tried quickly with non ideal connectors (brass banana), non ideal meter (34401a, the 7.5 meters are sleeping ::)). Heating for 30 sec with a hot air rework station at 100deg (the binding post was probably a lot cooler) I was able to get around 3uV offset. In 4W Ohm mode it's generating 1 to 2 ppm of noise.

Look like it's less of a problem in my case.
 

Offline dietert1

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #62 on: November 06, 2019, 08:58:07 pm »
Kosmic, this was for a binding post like the ones on the IET website you linked?

Meanwhile i found this table in a Keithley 2700 manual:

Table E-1   
Material thermoelectric coefficients   
   
Material                           Thermoelectric potential
Copper-Copper                    0.2 µV/°C
Copper-Silver                    0.3 µV/°C
Copper-Gold                    0.3 µV/°C
Copper-Cadmium/Tin            0.3 µV/°C
Copper-Lead/Tin                  1–3 µV/°C
Copper-Kovar                    40 µV/°C
Copper-Silicon                  400 µV/°C
Copper-Copper Oxide    1000 µV/°C

So it appears the thermal voltages i actual had in my setup (220 and 250 nV) are a good result even for a copper-to-copper contact.

Can anyone explain why Pomona and others use Cu-Te? Tellurium is listed with 500 uV/°C, so i'd guess even a small fraction of Te could distort everything.

Regards, Dieter
« Last Edit: November 06, 2019, 09:08:13 pm by dietert1 »
 

Offline razvan784

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #63 on: November 06, 2019, 09:48:13 pm »
So it appears the thermal voltages i actual had in my setup (220 and 250 nV) are a good result even for a copper-to-copper contact.
I get around 3 uV with Pomona 5291A cables (supposedly CuTe bananas with CuBe springs) stuck into a 34401A (Cu sockets). This is when heating the cable end that sticks into the meter with my fingers. I also see the opposite polarity when heating the other cable, and the offsets take several minutes to decay - which is to be expected.
I guess they are called "low emf" not "zero emf" for a reason :)
I get about the same behavior with Multi-Contact Multilam bananas (brass body, CuTe spring) and Multi-Contact LS4 (CuBe hollow bananas).
Edit: for comparison, I get around 9 uV for a Pomona 5291A stuck into a Pomona 3770 binding post (also supposedly CuTe), and on the order of 100 uV for a copper-Kovar junction (made with a pin from a hermetic transistor package -- like the LTZ1000 uses :) ). That is certainly not "low emf". So your binding posts are certainly not steel.

Can anyone explain why Pomona and others use Cu-Te? Tellurium is listed with 500 uV/°C, so i'd guess even a small fraction of Te could distort everything.
It's been discussed on this forum before, apparently the reason is mechanical. Pure Cu is hard to machine, CuTe is apparently much easier, while still retaining "low emf" characteristics.
« Last Edit: November 06, 2019, 10:15:28 pm by razvan784 »
 

Online Kosmic

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #64 on: November 07, 2019, 04:57:03 am »
Kosmic, this was for a binding post like the ones on the IET website you linked?

No, I got the old traditional ESI version.

 

Online MiDi

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #65 on: November 07, 2019, 08:50:27 am »
Can anyone explain why Pomona and others use Cu-Te? Tellurium is listed with 500 uV/°C, so i'd guess even a small fraction of Te could distort everything.

Someone mentioned Cu-Te is used for better machinability and I guess it is harder than pure copper.
For spring contacts e.g. in plugs there is often used Cu-Be, because it has better properties for that purpose.

I had searched for infos about T-EMF for these materials, but could not find anything.

Edit:
The T-EMF for copper to copper should depend on differences of the purity.
Theoretically if only copper from same batch is used the T-EMF would be 0.
« Last Edit: November 07, 2019, 08:57:13 am by MiDi »
 

Offline MegaVolt

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Re: ESI Resistance Standard SR1010 and Standard Resistor SR104
« Reply #66 on: November 08, 2019, 10:51:23 am »
Theoretically if only copper from same batch is used the T-EMF would be 0.
Any material is not only copper.
 


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