-
Is there toxic solder in an ESI SR1010?
Posted by
e61_phil
on 08 Apr, 2017 14:42
-
Hi,
I extracted this offtopic question out of the solartron thread.
I would like to modify the resistors in an ESI SR1010-10 transfer standard (build ~1962). Can anyone tell me, if there was toxic solder used? Like cadmium solder for low EMF or something like that or is it safe to desolder the resistors?
Thanks
Philipp
-
#1 Reply
Posted by
Vgkid
on 08 Apr, 2017 15:23
-
Why do you need to desolder the resistors?
-
#2 Reply
Posted by
e61_phil
on 08 Apr, 2017 16:11
-
Why do you need to desolder the resistors?
It is a 10R step version, but I don't have the shorting bars. Without these bars the unit is more or less useless for transfers. I would salvage the 10R resistors for other projects and replace them with hermetic 1k ones. However, I want to know if it is safe to solder inside an ESI SR1010.
-
-
To my knowledge, at least before the EU solder crazy happened, ESI used regular 60/40 lead/tin solder, currently I do not know for sure if they had to change over to a different solder. I have not worked on any 'newer' models but all the ones I have or have worked on were regular solder.
The SR1010 is still quite useful even without the shorting bars and the effort to remove those low ohm resistors from their mounts could likely change their values permanently.
-
-
I'd suggest you leave those resistors alone - that's a work of art that should be left un-touched. You'll never get those out without changing some of the TCR magic anyway.
On occasion I've seen those bars by themselves come up at auction, or maybe even leftover in a shop garbage can because someone didn't know what they were.
At the very least, see if you can have a set fabricated at a machine shop. Then you'd be good as new!
-
#5 Reply
Posted by
CalMachine
on 08 Apr, 2017 18:20
-
I'd suggest you leave those resistors alone - that's a work of art that should be left un-touched. You'll never get those out without changing some of the TCR magic anyway.
On occasion I've seen those bars by themselves come up at auction, or maybe even leftover in a shop garbage can because someone didn't know what they were.
At the very least, see if you can have a set fabricated at a machine shop. Then you'd be good as new!
Why do you need to desolder the resistors?
It is a 10R step version, but I don't have the shorting bars. Without these bars the unit is more or less useless for transfers. I would salvage the 10R resistors for other projects and replace them with hermetic 1k ones. However, I want to know if it is safe to solder inside an ESI SR1010.
I was just looking around for one here within the last few weeks, as well. I found that IET still sells them, but they are
extremely expensive.
http://www.ietlabs.com/shorting-bars.html
-
#6 Reply
Posted by
e61_phil
on 08 Apr, 2017 18:22
-
To my knowledge, at least before the EU solder crazy happened, ESI used regular 60/40 lead/tin solder, currently I do not know for sure if they had to change over to a different solder. I have not worked on any 'newer' models but all the ones I have or have worked on were regular solder.
The SR1010 is still quite useful even without the shorting bars and the effort to remove those low ohm resistors from their mounts could likely change their values permanently.
Thank you very much for this info! The SR1010 ist much older as the RoHS stuff. The verification sheet on the side is from April 1964. Excatly 55years ago
. Therefore, I think the soldering shouldn't take more effect on the resistors in absolute value than the 55 years.
I'd suggest you leave those resistors alone - that's a work of art that should be left un-touched. You'll never get those out without changing some of the TCR magic anyway.
On occasion I've seen those bars by themselves come up at auction, or maybe even leftover in a shop garbage can because someone didn't know what they were.
At the very least, see if you can have a set fabricated at a machine shop. Then you'd be good as new!
To clarify what I will do: I'm not that much interested in the 10R resistors (I don't want to throw them away, of course). I want to use this very nice case with 4 wire contacts to every resistor. And I want to equip higher value resistors (1k).
The resistors are specified with 1ppm/K. Do you think that will also change, if I desolder them? (This would be a pity, but not that important for what I want to do.)
I was just looking around for one here within the last few weeks, as well. I found that IET still sells them, but they are extremely expensive.
http://www.ietlabs.com/shorting-bars.html
Do you have a price?
-
#7 Reply
Posted by
CalMachine
on 08 Apr, 2017 18:26
-
I was just looking around for one here within the last few weeks, as well. I found that IET still sells them, but they are extremely expensive.
http://www.ietlabs.com/shorting-bars.html
Do you have a price?
$1,350
-
#8 Reply
Posted by
e61_phil
on 08 Apr, 2017 18:28
-
$1,350
The shorting bar only?
Furthermore, I can't believe that a 100R to 0,1R transfer within 1ppm is possible. 1ppm of 0,1R are only 100nR. Even with a good shorting bar it will be very hard to achieve.
-
-
Welcome to the world of low ppm <Laughing>.
Depending on what you're doing, you might need a lead compensator to accurately compare between two dividers. Several on eBay right now, and they are worth having if you're working with precision dividers, KVD's, etc.
At 55 yrs old, that SR unit is settled in just fine and will be stabilized - and valuable as-is. Just an idea: Have you looked around to maybe find another volt/resistance-nut willing to trade?
-
#10 Reply
Posted by
Vgkid
on 08 Apr, 2017 19:12
-
I believe that Doktor Pyka had a set made. Send him a pm.
-
#11 Reply
Posted by
e61_phil
on 08 Apr, 2017 19:13
-
I believe that Doktor Pyka had a set made. Send him a pm.
A set of what?
-
-
If you are looking for a set of resistors @ 1k, you may find parts from a Fluke 720A, DEKAPOT, or similar device a cheaper choice. They are already connected together and you just need to add the additional wires for the 4-W connection. Finding them at 1ppm/C spec may be difficult. They may also be matched TCR sets.
-
#13 Reply
Posted by
e61_phil
on 08 Apr, 2017 19:25
-
I don't need a set of resistors. I have a lot of hermetic sealed one. What I need is a nice housing with low thermal jacks. Therefore, I want to use the housing of the SR1010
-
#14 Reply
Posted by
Vgkid
on 08 Apr, 2017 19:34
-
I believe that Doktor Pyka had a set made. Send him a pm.
A set of what?
Shorting bars.
-
#15 Reply
Posted by
Kleinstein
on 08 Apr, 2017 19:50
-
Even when used the SR1010-10 seems to have a significant value.
http://www.used-line.com/list-calibrators/standards-resistors/esi-sr1010 The old age can even be an advantage as the resistors have settled. It's only the calibration that might be a little outdated. There might have be changes in the Ohms definition in between.
Soldering the 10 Ohms resistors could ruin there stability / adjustment. Also the 4 point 0 Ohms junctions will likely suffer a lot.
For soldering the 1 K resistors, it depends on there case. In general they tend to be less sensitive, as the main part that changes is the external wire. So more like similar absolute change as with the 10 Ohms.
-
#16 Reply
Posted by
e61_phil
on 08 Apr, 2017 20:14
-
-
#17 Reply
Posted by
CalMachine
on 08 Apr, 2017 21:38
-
Even when used the SR1010-10 seems to have a significant value.
http://www.used-line.com/list-calibrators/standards-resistors/esi-sr1010
Hehe, I will sell it immediately for the half of that price 
Ok guys, I understand! I won't touch the SR1010.
Thanks
Philipp
That's probably a good idea! They are great metrology artifacts in my eyes
And yes, the $1,350 was just for a set of shorting bars. Then there are a few parallel / series-parallel adapters you can get. There a few of those on ebay right now for ~$200. The shorting bars are what seem to be the hard thing to find. Once I get the adapters, I'm going to use our SR1010 with traceability our 10k Standard to step up to 100k and down to 1k.
-
-
-
#19 Reply
Posted by
e61_phil
on 09 Apr, 2017 06:11
-
These shorting bars might work for higher values, but for the 10Ohm/step version? I can't believe that. Has anyone such a shorting bar and can measure the resistance between the shorting bar and the connected jack?
I think anything above 10µR between these 0R junctions and the shorting bars will ruin your 1ppm 1:100 ratio
-
#20 Reply
Posted by
ap
on 09 Apr, 2017 07:27
-
I measured about 30 uOhms (with a 34420A, and the original 10 Ohms SR1010 and shorting bars; hard to measure precisely of course). The manual states 50 uOhms appr. value. As per their spec, and I have never checked / questioned their calculation, as I would think errors would have been identified by now, this still leads to the 1ppm spec you referred to.
In any case, the 10 Ohms SR1010 is a very good way to transfer 100 ohms to a precision 1 ohms resistance standard such as a Leeds&Northrup 4210. So no good idea to destroy it. Good you are beyond that.
Building a shorting bar yourself is ok, but no way arround heavy gold plating.
-
#21 Reply
Posted by
manganin
on 09 Apr, 2017 07:30
-
I would salvage the 10R resistors for other projects and replace them with hermetic 1k ones.
If you need a 1 kohm SR-1010, I have a duplicate. Late version, blue body / black face.
Please don't ruin the 10 ohm unit.
-
#22 Reply
Posted by
e61_phil
on 09 Apr, 2017 09:05
-
I measured about 30 uOhms (with a 34420A, and the original 10 Ohms SR1010 and shorting bars; hard to measure precisely of course). The manual states 50 uOhms appr. value. As per their spec, and I have never checked / questioned their calculation, as I would think errors would have been identified by now, this still leads to the 1ppm spec you referred to.
In any case, the 10 Ohms SR1010 is a very good way to transfer 100 ohms to a precision 1 ohms resistance standard such as a Leeds&Northrup 4210. So no good idea to destroy it. Good you are beyond that.
Building a shorting bar yourself is ok, but no way arround heavy gold plating.
Very intersting, thanks! I found the picture attached in the manual. They say (as you already said) around 50µR in series in R/10 configuration. R/10 is 1R with the SR1010-10 model. Therefore, additional 50µR should add 50ppm to 1R. How can one achieve 1ppm transfer with something like that?
-
#23 Reply
Posted by
Kleinstein
on 09 Apr, 2017 10:50
-
There might be a way to get less of the contact resistance, by using a different scheme for the voltage sensing contacts: that could be similar the Thomson bridge circuit, with averaging resistors and taking the voltage from the other contacts of the resistors - thus taking advantage of the 4 - terminal zeros.
-
#24 Reply
Posted by
e61_phil
on 09 Apr, 2017 10:56
-
Sorry, there is schematic above the picture. They use the shorting bars and a compensation network. In that circuit there is no addionational 50µR shown. Very interesting..