Is there toxic solder in an ESI SR1010? - Page 1
Forum section: electronics / general

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 08, 2017, 02:42:31 pm
content: 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?ThanksPhilipp

author: Vgkid
author_rank: Super Contributor
timestamp: April 08, 2017, 03:23:01 pm
content: Why do you need to desolder the resistors?

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 08, 2017, 04:11:58 pm
content: Quote from: Vgkid on April 08, 2017, 03:23:01 pmIt 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.

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: April 08, 2017, 05:37:19 pm
content: 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.

author: MisterDiodes
author_rank: Frequent Contributor
timestamp: April 08, 2017, 06:08:43 pm
content: 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!

author: CalMachine
author_rank: Frequent Contributor
timestamp: April 08, 2017, 06:20:10 pm
content: Quote from: MisterDiodes on April 08, 2017, 06:08:43 pmQuote from: e61_phil on April 08, 2017, 04:11:58 pmI was just looking around for one here within the last few weeks, as well. I found that IET still sells them, but they areextremelyexpensive.http://www.ietlabs.com/shorting-bars.html

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 08, 2017, 06:22:42 pm
content: Quote from: Edwin G. Pettis on April 08, 2017, 05:37:19 pmThank 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.Quote from: MisterDiodes on April 08, 2017, 06:08:43 pmTo 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.)Quote from: CalMachine on April 08, 2017, 06:20:10 pmDo you have a price?

author: CalMachine
author_rank: Frequent Contributor
timestamp: April 08, 2017, 06:26:00 pm
content: Quote from: e61_phil on April 08, 2017, 06:22:42 pm$1,350

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 08, 2017, 06:28:48 pm
content: Quote from: CalMachine on April 08, 2017, 06:26:00 pmThe 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.

author: MisterDiodes
author_rank: Frequent Contributor
timestamp: April 08, 2017, 06:51:55 pm
content: 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?

author: Vgkid
author_rank: Super Contributor
timestamp: April 08, 2017, 07:12:13 pm
content: I believe that Doktor Pyka had a set made. Send him a pm.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 08, 2017, 07:13:37 pm
content: Quote from: Vgkid on April 08, 2017, 07:12:13 pmA set of what?

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: April 08, 2017, 07:22:53 pm
content: 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.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 08, 2017, 07:25:47 pm
content: 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

author: Vgkid
author_rank: Super Contributor
timestamp: April 08, 2017, 07:34:50 pm
content: Quote from: e61_phil on April 08, 2017, 07:13:37 pmShorting bars.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 08, 2017, 07:50:37 pm
content: Even when used the SR1010-10 seems to have a significant value.http://www.used-line.com/list-calibrators/standards-resistors/esi-sr1010The 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.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 08, 2017, 08:14:36 pm
content: Quote from: Kleinstein on April 08, 2017, 07:50:37 pmHehe, I will sell it immediately for the half of that priceOk guys, I understand! I won't touch the SR1010.ThanksPhilipp

author: CalMachine
author_rank: Frequent Contributor
timestamp: April 08, 2017, 09:38:02 pm
content: Quote from: e61_phil on April 08, 2017, 08:14:36 pmThat's probably a good idea! They are great metrology artifacts in my eyesAnd 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.

author: MisterDiodes
author_rank: Frequent Contributor
timestamp: April 08, 2017, 10:45:42 pm
content: Here - You might get a quote from your machine shop, or make some yourself - drawing included:http://rfscientific.eu/esi-sb103-shorting-barshttps://www.eevblog.com/forum/metrology/esi-resitance-standard-sr1010-and-standard-resistor-sr104/

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 09, 2017, 06:11:36 am
content: 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

author: ap
author_rank: Frequent Contributor
timestamp: April 09, 2017, 07:27:20 am
content: 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.

author: manganin
author_rank: Regular Contributor
timestamp: April 09, 2017, 07:30:56 am
content: Quote from: e61_phil on April 08, 2017, 04:11:58 pmIf 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.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 09, 2017, 09:05:01 am
content: Quote from: ap on April 09, 2017, 07:27:20 amVery 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?

author: Kleinstein
author_rank: Super Contributor
timestamp: April 09, 2017, 10:50:54 am
content: 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.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 09, 2017, 10:56:19 am
content: 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..

author: CalMachine
author_rank: Frequent Contributor
timestamp: April 09, 2017, 02:21:08 pm
content: Quote from: e61_phil on April 09, 2017, 10:56:19 amhttp://www.ietlabs.com/esi-sr1010-resistance-transfer-standard.htmlCheck out the accessories tab.

author: manganin
author_rank: Regular Contributor
timestamp: April 27, 2017, 01:18:47 pm
content: Quote from: manganin on April 09, 2017, 07:30:56 amNot available anymore.Posted today to e61_phil (Germany).Before shipping I checked the first ten sections in series (binding posts A0/B0 --- A10/B10) against a calibrated SR104.-11,3 ppm 02/1995 (old cal certificate)and 22 years later:-13,5 ppm 04/2017Good chances that in addition to a ratio device, it can serve as a decent 10 kohm standard as well.

author: dacman
author_rank: Frequent Contributor
timestamp: April 27, 2017, 11:51:03 pm
content: The shorting bars have the sense terminals, not the current terminals, therefore they do not add (as much) to the resistance.The PC101 Parallel Compensation Network is for paralleling ten resistors and it's also where the current is applied. It plugs into the center binding posts.The SPC102 Series Parallel Compensation Network is for 3R || 3R || 3R, and also has the current terminals.100:1 Parallel spec is 1 PPM + 0.1 uOhm (or 2 PPM at 0.1 Ohm).10:1 Series Parallel spec is 1 PPM + 1 uOhm.There are no shorting bars nor compensation networks for using 10 resistors in series.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 28, 2017, 10:18:53 am
content: Quote from: dacman on April 27, 2017, 11:51:03 pmThey add resistance due to the plugs. This is also described in the SR1010 manual.Quote from: dacman on April 27, 2017, 11:51:03 pmThis should compensate for these errors. Does anyone know what's inside the PC-101?

author: manganin
author_rank: Regular Contributor
timestamp: April 28, 2017, 10:55:58 am
content: Quote from: e61_phil on April 28, 2017, 10:18:53 am0,2 ohm 500 ppm resistors which connect in series with the contact resistance to make sure that it doesn't affect the current distribution.

author: mc172
author_rank: Frequent Contributor
timestamp: April 28, 2017, 11:34:37 am
content: If a few people want some of these shorting bars I could make some for forum members on my manual milling machine. How many people are interested? If more than say five people want a set I'm willing to do it.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 28, 2017, 03:50:20 pm
content: Quote from: manganin on April 28, 2017, 10:55:58 amThanks! Now, I understand how it works.Quote from: mc172 on April 28, 2017, 11:34:37 amDepends on costs and material/finish.I played around with LTSpice and the compensation resistors seems not very crucial, but the contact to the shorting bars seems to be very crucial. 100µR per contact leads to a 100:1 error of 1,5ppm for 10R/Step

author: mc172
author_rank: Frequent Contributor
timestamp: April 28, 2017, 10:55:34 pm
content: I can make it out of whatever you want, within reason. Stainless steel, brass, copper, no problem.I'd prefer to not have to send it to a plating shop but me what you want and I'll suggest how much it'll cost. I doubt it'll be more than £200 for a set, though, unless the thickness gets to 6 mm or more. The drawing MisterDiodes linked to suggests 2 mm thickness. I don't actually know anything about the ESI SR1010 so 6 mm might be way too thick, I have no idea.

author: dacman
author_rank: Frequent Contributor
timestamp: April 28, 2017, 11:10:06 pm
content: The shorting bars do connect the parallel resistors which adds resistance, but the 100 uR spec is from end to end. (Gold tends to make a very good connection, and I clean the connections with a cotton swab with a very little bit of mineral oil to clean off any grit and to keep from scraping up the gold.)

author: CalMachine
author_rank: Frequent Contributor
timestamp: April 28, 2017, 11:21:48 pm
content: Quote from: mc172 on April 28, 2017, 11:34:37 amI would be interested in a set

author: babysitter
author_rank: Frequent Contributor
timestamp: April 29, 2017, 08:42:22 am
content: I aquired some 2mm copper sheet from egay, and the local locksmith was able to cut it according to a eagle drawing. Still missing connectors (I used the existing 4mm ones of the SR1010) and gold plating. Will post the eagle board drawing sometime in the next... 2 years.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 29, 2017, 08:49:10 am
content: Quote from: babysitter on April 29, 2017, 08:42:22 amDid you measure the resistance between two connected sockets? For the SR1010-10Ohm/Step it should be really low (<=2*50µR). And without the PC-101 you will get about 20ppm of error for a 100:1 transfer, even with below 50µR contact resistance. Would be really interesting if gold plating is needed.

author: manganin
author_rank: Regular Contributor
timestamp: April 29, 2017, 10:21:00 am
content: I have succesfully used 30x3 flat copper bar. Thicker than that will eventually ruin the binding post threads.Rigid enough and provides lower resistance than the original. Used in power bus bars and therefore easily available.From the home machinist point of view the 1:100 only type is much easier make: only six slots 7,0 diameter and 8,0 deep measured from the edge.

author: e61_phil
author_rank: Frequent Contributor
timestamp: April 29, 2017, 10:35:18 am
content: Isn't it possible to drill holes in the copper bar only? Not very comfortable to unscrew every binding post, but it will be very easy to build at home.

author: ap
author_rank: Frequent Contributor
timestamp: April 29, 2017, 11:58:39 am
content: Sure, you could just drill, much easier. However, you still need the gold plating. And it needs to be relatively thick too, to avoid abrasion.

author: manganin
author_rank: Regular Contributor
timestamp: April 29, 2017, 01:49:01 pm
content: Quote from: e61_phil on April 29, 2017, 10:35:18 amSix holes in copper in a straight line evenly spaced may sound easy. Until you start to drill.The manufacturing tolerance defines the contact area of each connection.Machine with a coordinate table is a must.

author: quarks
author_rank: Frequent Contributor
timestamp: May 01, 2017, 09:29:47 am
content: just in case anyone needs this information:original shorting bar SB 103 has 1.7mm thickness

author: CalMachine
author_rank: Frequent Contributor
timestamp: May 21, 2017, 01:20:37 am
content: Quote from: quarks on May 01, 2017, 09:29:47 amI'm curious... does anyone know the thickness of the gold plating used for these type of connections? For some reason in the back of my memory bank, I've got 0.15 microns thickness rolling around. I'm trying to get a set of these shorting bars made ASAP and could use as much info as possible.

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: May 21, 2017, 04:24:00 am
content: Back in the good old days, the standard gold plating was 50 microinches, in some instances it would be specified thicker but 50 was the 'gold standard' <grinning>.

author: CalMachine
author_rank: Frequent Contributor
timestamp: May 21, 2017, 01:29:21 pm
content: Quote from: Edwin G. Pettis on May 21, 2017, 04:24:00 amAnd that is gold plated directly onto the copper? Or does there require an intermediate layer?

author: Andreas
author_rank: Super Contributor
timestamp: May 21, 2017, 02:06:42 pm
content: Hello,You will need a Ni plating first on copper to apply Au.With best regardsAndreas

author: CalMachine
author_rank: Frequent Contributor
timestamp: May 21, 2017, 02:19:06 pm
content: Quote from: Andreas on May 21, 2017, 02:06:42 pmhttp://www.lowthermal.com/pdf/2758-series-data.pdf,How did they get away with not using nickel in these? I would not like to introduce nickel, if possible. Would that even matter here? Is there nickel in gold plating on the bindings that ESI used?

author: Andreas
author_rank: Super Contributor
timestamp: May 21, 2017, 02:22:09 pm
content: Hello,Thats the usual procedure for durable gold layers on copper contacts.Otherwise the gold layer will not last long.with best regardsAndreas

author: Robert763
author_rank: Super Contributor
timestamp: June 04, 2017, 10:12:50 pm
content: Hi,I'd be interested in pair of shorting bars.I really miss having access to the prototype machine shop at my last employer. My current employer has lots of machines but as a designer I'm not allowed to use a pillar drill for work, never mind a mill for a homerhttps://www.eevblog.com/forum/Smileys/default/sad.gifI 'm a new owner of a SR1010-100 (early ESI model). Picked it up today at the Spalding radio rally allong with two GR 1409-U standard capacitors (0.2uF 0.05%). I saw the first capacitor and the seller said " I've a couple of other bits like that" and produced the second capacitor and the SR1010. I asked how much and tried not to show two much surprise when he said £3 each for the capacitors and £15 for the SR1010https://www.eevblog.com/forum/Smileys/default/smiley.gifG8RPI.

author: 0.01C
author_rank: Regular Contributor
timestamp: June 05, 2017, 03:30:44 am
content: Quote from: Robert763 on June 04, 2017, 10:12:50 pm£15 for a SR1010,very good price