Author Topic: ESI SR104 leaking oil  (Read 860 times)

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Offline nikonoid

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ESI SR104 leaking oil
« on: December 03, 2017, 06:51:05 AM »
I recently acquired a used SR104 10k resistor. To my surprise it came with signs of leaking oil. See the photos.

There is definitely some oil still left on the inside as I can hear it slashing and bubbling if I tilt the box a bit over 45 degrees, left then 45 degrees right.

Have you ever heard about something like that?
Does your SR104 make a slashing noise, if you dear to tilt it?
What can I do to troubleshoot?


I got a calibrated Keithley 2002 and a not yet calibrated 3458a. I measured the resistor with K2002 and it seems to have right value. I read it at +3.1 ppm. My k2002 was reading +2.7ppm low (on 20k range, same temp) during recent calibration. This makes this resistor approx +5.8 high, minus 1.7ppm 1990 adjustment, divided by 49 years (manufactured in 1968 and rated as +0.00ppm at that time) gives +0.08 ppm per year.  I know using K2002 for this is very crude, but this is the best I have.

Should I try to assess temperature coefficient? Monitor stability? Thank you very much.

 

Offline CalMachine

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Re: ESI SR104 leaking oil
« Reply #1 on: December 03, 2017, 06:58:38 AM »
Good pickup!   :-+  The one we've got at the lab doesn't exhibit the sloshing, bubbling, or signs of leaking.  It definitely sounds like you've had a significant amount of oil loss.   I never tore ours down, so I've only seen the insides from posts here on EEVblog.  If you don't need those stickers intact, it might not hurt to investigate a little further.
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Offline DiligentMinds.com

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Re: ESI SR104 leaking oil
« Reply #2 on: December 03, 2017, 07:01:52 AM »
All of my SR-104's have this "sloshing noise"-- yes, you can hear the oil moving around inside-- that is normal.

I don't think your resistor is leaking oil from inside-- I think someone put oil in the temperature well, and then forgot to remove it-- so when you tip the unit over it is leaking out of the well-- not out of the hermetically sealed enclosure inside.  I use 99% IPA instead of oil for this reason-- oil is just too messy.  The temperature well is normally only used during calibration of the internal temperature sensor-- by placing a calibrated SPRT in the well.  This is only done if you ask the Cal-Lab to do it.

You might want to clean up your unit and remove the oil from the well as best you can.

Don't worry, everything is OK !!!
 

Offline ManateeMafia

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Re: ESI SR104 leaking oil
« Reply #3 on: December 03, 2017, 07:46:20 AM »
nikonoid,

That was a good find and I hope DiligentMinds is correct. Your resistor is a couple of months older than mine and was just calibrated at Process Instruments.

If you contact PI, they can give you a quote to measure the TCR. The pricing is competitive and about half of what IET would charge you.
 

Offline Twoflower

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Re: ESI SR104 leaking oil
« Reply #4 on: December 03, 2017, 08:27:33 AM »
To check if there's enough oil in it: Why not compare the weight of the unit with the ones of the others here? Probably there's no need to use a metrology class balance.
 
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Offline nikonoid

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Re: ESI SR104 leaking oil
« Reply #5 on: December 03, 2017, 09:26:36 AM »
Thank you, guys.

CalMachine: I am not sure, if I am ready to open mine.  ;)  I saw the resistor tear down thread you are taking about. When I was poking around the web, I found the photo of the insides of SR104. I just sharpened it a bit. It is attached if anyone is interested. When looking really carefully I can see 10 of 999R475 resistors, two trimmer resistors and two black temperature sensors, in possibly Teflon stands.

DiligentMinds.com: This sounds encouraging. I have a resistor laying on its side for few hours to see if there is any additional oil leak.

ManateeMafia: I will look into PI. I am afraid the calibration could cost as much as resistor itself. It was calibrated by Agilent in 2004. I am wondering if there is any way to get a copy of that cal certificate.

Twoflower: This is a brilliant idea! I will get a reasonable scale on Monday and publish results.

I have three Vishay 10K z-foil resistors with extremely stable tempco, and also 10K SR1010. I am considering measuring them against each other to tempco and stability comparison.
 
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Offline Edwin G. Pettis

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Re: ESI SR104 leaking oil
« Reply #6 on: December 03, 2017, 11:03:51 AM »
None of the SR-104s I've used have ever had sloshing, that is not normal, brand new SR-104s do not slosh, my SR-104 does not slosh.  While the oil is present for thermal considerations, imparting a large thermal mass to slow down temperature variations, the lack of 100% oil will not directly affect the resistors themselves.  If the power levels are kept to a normal minimal amount, say less than 100mW as is the usual procedure, there will be no danger to the resistors.  If you have a leaky SR-104 and it keeps leaking, the only alternative is to find the leak and seal it, however if you observe normal operating procedures, you will not cause any harm or change to the resistors, just expect them to react to temperature changes quicker than normal.  You will have to give the SR-104 some time to stablize at whatever power level you're using since there will be reduced time lag.  The lack of full oil will not affect the resistor's characteristics as such, just how fast they respond to temperature and power.

The main question is why is it leaking and what caused the leak?  If it was caused by dropping for instance, there is always the possibility that something inside has been affected, including one or more resistors depending on how hard the jolt was.  Only time and measurements will tell.
 
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Online chuckb

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Re: ESI SR104 leaking oil
« Reply #7 on: December 03, 2017, 12:01:48 PM »
Reference the attached Vishay VHP document. On page 5, table 5 the last item is a 999.475 ohm resistor, 0.05% tolerance. Manufactured for somebody in sets of 10.

From the IET product page for the SR-104. The ESI and TEGAM version of the SR-104 10k ohm standard used mica card wirewound resistors.

"The NEW SR102, SR103 and SR104 are no longer designed using Evanohm-R wire but instead use 10 custom hermetically sealed oil-filled resistors. Each resistor is individually tested and then combined in sets that are matched for absolute tolerance and temperature coefficient. These sets are then allowed to age typically for several years before use.

The resistors are still connected in series, parallel, or series-parallel to achieve the final resistance value. The set of 10 resistors are then hermetically sealed in the same esi stainless steel oil-filled housing. This efficiently dissipates heat into a larger mass and keeps all of the resistors at the same temperature. Each SR102, SR103 and SR104 is tested using an MI6010 and transfer standards that are calibrated annually by primary standards labs such as NRC. Typical calibration uncertainty is < 0.4 ppm."

Anybody know when the changeover happened? Maybe it was a year or two after the January 2007 purchase from Tegam.
 
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Online Vgkid

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Re: ESI SR104 leaking oil
« Reply #8 on: December 03, 2017, 12:08:07 PM »
I only noticed the sr10X change a few months ago. I guess they ran out of aged/stable components.
Anyone know what is inside the srl series?
If you own any North Hills Electronics gear, message me.
 

Offline DiligentMinds.com

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Re: ESI SR104 leaking oil
« Reply #9 on: December 03, 2017, 01:23:06 PM »
Thank you, guys.

CalMachine: I am not sure, if I am ready to open mine.  ;)  I saw the resistor tear down thread you are taking about. When I was poking around the web, I found the photo of the insides of SR104. I just sharpened it a bit. It is attached if anyone is interested. When looking really carefully I can see 10 of 999R475 resistors, two trimmer resistors and two black temperature sensors, in possibly Teflon stands.

DiligentMinds.com: This sounds encouraging. I have a resistor laying on its side for few hours to see if there is any additional oil leak.

ManateeMafia: I will look into PI. I am afraid the calibration could cost as much as resistor itself. It was calibrated by Agilent in 2004. I am wondering if there is any way to get a copy of that cal certificate.

Twoflower: This is a brilliant idea! I will get a reasonable scale on Monday and publish results.

I have three Vishay 10K z-foil resistors with extremely stable tempco, and also 10K SR1010. I am considering measuring them against each other to tempco and stability comparison.

This looks like it was put together by Awesome14 !!!  :palm:

I guess that people that like sausage, should never visit the sausage factory...

Now, why in hell would they put hermetic resistors inside of another hermetic can?   :-//

EDIT ::

Oops-- just read the post above.  I guess this construction is the "new method".  All of my SR104's are very old models from ESI-- so probably made with the old method with Evanohm wire on mica cards.  These old resistors are scary stable-- I wonder if the new ones made with VPG resistors are as stable with respect to time... ?  :-//
« Last Edit: December 03, 2017, 01:29:37 PM by DiligentMinds.com »
 

Offline manganin

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Re: ESI SR104 leaking oil
« Reply #10 on: December 03, 2017, 10:14:26 PM »
Quote from: IET
The NEW SR102, SR103 and SR104 are no longer designed using Evanohm-R wire but instead use 10 custom hermetically sealed oil-filled resistors.

Of course they ruined that too.

Quote from: IET
IET continues to manufacturer the SR102 & SR104 to the same exacting specs as esi/Tegam

The specification is 0.5 ppm/year but a typical ESI made SR104 shows drift almost ten times better and predictable. And continues to do so for decades and probably centuries.

I recently acquired a used SR104 10k resistor. To my surprise it came with signs of leaking oil.

The oil left in the thermometer well is the most likely explanation for the leakage. But if you are very unlucky, cold non-pressurised air shipping can actually crack the glass hermetic seal. Most vulnerable are the resistors manufactured prior 1972-1973 which have the feed throughs attached directly to the steel container. Brass supporting rings were added later.

Does your SR104 make a slashing noise, if you dear to tilt it?

There needs to be some air to allow the oil thermal expansion without explosion. If you tilt it fast enough you can hear the slashing or whatever you call it.

 

Offline CalMachine

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Re: ESI SR104 leaking oil
« Reply #11 on: December 05, 2017, 04:19:48 AM »
I had a chance of measuring our standard SR104 today.

With lid - 5577.5 g
Without lid - 4658.4 g
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Offline nikonoid

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Re: ESI SR104 leaking oil
« Reply #12 on: December 05, 2017, 02:00:07 PM »
Reference the attached Vishay VHP document. On page 5, table 5 the last item is a 999.475 ohm resistor, 0.05% tolerance. Manufactured for somebody in sets of 10.

From the IET product page for the SR-104. The ESI and TEGAM version of the SR-104 10k ohm standard used mica card wirewound resistors.

"The NEW SR102, SR103 and SR104 are no longer designed using Evanohm-R wire but instead use 10 custom hermetically sealed oil-filled resistors. Each resistor is individually tested and then combined in sets that are matched for absolute tolerance and temperature coefficient. These sets are then allowed to age typically for several years before use.

The resistors are still connected in series, parallel, or series-parallel to achieve the final resistance value. The set of 10 resistors are then hermetically sealed in the same esi stainless steel oil-filled housing. This efficiently dissipates heat into a larger mass and keeps all of the resistors at the same temperature. Each SR102, SR103 and SR104 is tested using an MI6010 and transfer standards that are calibrated annually by primary standards labs such as NRC. Typical calibration uncertainty is < 0.4 ppm."

Anybody know when the changeover happened? Maybe it was a year or two after the January 2007 purchase from Tegam.

That is a very interesting find. The tempco in spec is much worse. I guess Tegam conditions, monitors and selects resistors for better performance.

BTW, resistors in Tegam photo have 0.047% tolerance, not 0.05%, but close enough...
 


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