Test Equipment Anonymous (TEA) group therapy thread

[d-el]

Kelvin wires:
- raw copper wires with Teflon insulation
- copper lugs
- Pomona 4892 banana
- Mueller copper alligator
- Sn81/Bi19 solder
- copper shielding from coax cable

[TERRA Operative]

Where did you get the teflon wire? And what did you use to strip the plating from the lugs?

I've been thinking of making my own kelvin cable for a while now too.

[Cyclotron]

Hydrochloric acid (HCl, muriatic acid) to remove tin from copper lugs. You can also use friction methods, such as media blasting.
If you use acid, please do so with care and preparation.

What was the solder used for? Also interested in the cable.

I've used this with good results:
https://www.ebay.com/itm/163693011252?var=463177839477

[d-el]

Where did you get the teflon wire? And what did you use to strip the plating from the lugs?

Teflon wire — Soviet МГТФ 0.020 wire.
I etched the terminal plating with nitric acid (HNO3), concentration about 20-30%.

[d-el]

What was the solder used for?

For solder wire to lugs.

I chose the heaviest lugs, specifically for wire cross-sections of 5-10 mm^2, so crimping won't work. Terminals with a cross-section of 0.5-1.0 mm^2 are too thin and narrow.

[m k]

Can you access cal data?
Are those models equal enough that cross comparing used currents can be meaningful?
Assuming here that the resistor value is pretty stable.

I have two HP 34401A and Fluke 8505A models, but environment is not very stable and some machines have been off for too long.
One article opinioned that drying after long off period must be at least few weeks.

For the wires,
I read that better leave wires loose than knit them side by side.
Intuition says that twisted pair is even better.

Some time ago around here was an active situation of good 4-wire shorts.
It went pretty far to nA level, or lower.
Then somebody opened HP's own 4-wire short and now the situation is pretty passive.

[d-el]

Can you access cal data?
Are those models equal enough that cross comparing used currents can be meaningful?

K2001 support read cal data by GPIB. But what to use it for?
Ohms current generator is not very absolutely precision, but very stable. Absolutely currency value depend direct from feedback resistor (Vishay Metal foil).

Range	K2001	K2010
20/10Ohms	9.2mA	10mA
200/100Ohms	0.98mA	1mA

[m k]

For guesstimation of how far they are from the spot.

[d-el]

I need to replace the o-ring; the old one is damaged. I'll also change the oil. Will regular transformer oil do?
Does anyone know what the oil level should be?

[Robert763]

I need to replace the o-ring; the old one is damaged. I'll also change the oil. Will regular transformer oil do?
Does anyone know what the oil level should be?

No, not transformer oil. The correct oil is food / medical grade refined mineral oil. This comes under different names in different countries. In the UK it's called liquid paraffin in other countries white mineral oil. It is used as a laxative for humans and horses. Small quantities can be bought from a pharmacy but larger quantities are reportedly cheaper from equine suppliers.

The level should be enough to fully cover the resistor but leaving an airspace of at least 10% of the volume of oil to allow for expansion. The exception to this is if the housing has a bellows to allow expansion but this is rare.

I note that the actual resistor is a Julie Research Labs item. One of the better makes.

[Vince]

I might be in an on-going effort to downsize my TE collection, starting with the largest and heaviest pieces, but that doesn't mean I don't keep en eye out for the odd piece that might find my fancy, especially if it's small and light and affordable.

So, when I found this puppy on leboncoin.fr, I just could not resist.  One more piece in my collection of '90s Metrix ASYC meters.

An MX51Ex, the ATEX version of the MX 50/51/52 series.
I have a thing for these somehow (I already have an MX57Ex, the ATEX version of the MX53/54/56 series)

The ad didn't look like much : a single picture of the thing, turned off, not much infos in the description.
But it looked in really good nick and was more than fairly priced (by French standards at least), at 75 Euros. Still for the sake of it I tried to bargain the seller, somehow it worked and I got it for only 60 Euros + 5 Euros shipping.

When I received it, I was shocked : this thing doesn't just look "nice", it's actually brand new from all I can see ! 
Not only is it 100% percent cosmetically, but also, the sides of the case have absolutely ze-ro screw driver / prying marks ! This is absolutely impossible on these meters because nobody knows how to open them the proper/intended way, which does not involve any screwdriver prying...

Also, buckle up, the LCD still has its protective film on it ! 

It also came with the original, still sealed, little plastic bag containing spare fuses.

The meter unsurprisingly doesn't turn on. I cracked it open and there was an Energizer 9V battery in it, with 1.25V left at its terminals and a "best before" date of 2004 ! So most likely the original battery that was installed at the factory.

I enjoy the H/W particularities of ATEX meters, somehow. Makes them a bit special / out of the ordinary 
The rubber piece that covers the entire battery/fuses compartment for IP purposes, is there, as with any of these meters.
However once you remove it, there is an extra cover that goes over the battery and 500mA fuse. Hard clear plastic, secured with a BTR metal screw into a beefy brass metal insert. The 500mA fuse has a very unusual form factor as you can see. Looks like a soldered / leaded yellow plastic capacitor or something. Good luck finding one of those I guess ! So I am extremely glad that the meter came with a spare one of those.

What surprised me is that although the meter, being an ATEX, has its 10A input deleted / input jack plugged, and the function switch does not allow to select 10A of course... as you can see the 10A fuse is nonetheless present inside the meter for some reason ! And the bag with the spares also provides a 10A fuse !
Weird....
I might crack it open fully to check traces and components on the PCB, to see if there are more traces left of the 10A range other than the fuse...

It also came with the paper work, untouched : a cal certificate, user manual and an ATEX booklet detailing the conformance certificates. One for coal mines and another for explosive environments. The accompanying leather case is also like new.

Also comes with the original test leads, which are crap, as always. I have never understood why Metrix made such nice meters, sold for a lot of money (I remember in 2015, Farnell was still selling the MX57Ex, for around 2 grand no less !!! ). It's not like they were in the "budget" meter business...

Anyway, I am super happy to have found this little gem, a beautiful addition to my Metrix collection, that will be cherished...

An excellent X-mas present to myself, for not a lot of money at that. Me happy.   

I also have a couple MX52 which I could now sell I guess, or maybe keep for parts to keep the MX51Ex going long term.

I put a new(er) battery in the thing, also an Energizer as it happened, expired in 2021 with 8.17V left, meter seems to be fine 
Somehow, no corrosion traces on the battery contacts from the 25 year old factory battery. Only a tiny bit of corrosion on one of the terminals of the battery itself but that was about it.

[d-el]

Robert763, thank you for the information. I found it at a local pharmacy nearby. Here it's called "Олія Вазелінова", the ingredients list says "Paraffinum Liquidum". To the left is the drained oil, you can see that it is yellow, but it smells a little
I refilled one resistor.

Like the design of this resistor better. The cap is threaded, and the smooth edge fits into the cap groove. No rubber seals, just simple assembly. The other resistors require an O-rings.

[TERRA Operative]

Glancing at that thumbnail, I though it was a tequila shot.

[m k]

The 500mA fuse has a very unusual form factor as you can see. Looks like a soldered / leaded yellow plastic capacitor or something.

Littelfuse and Bussmann are notorious makers.

https://www.littelfuse.com/products/fuses-overcurrent-protection/fuses/hazardous-area-type-fuses/pico-259

BAS Ex 832302
https://hubbellcdn.com/certificationdoc/TX6363_01-Sira-02ATEX2162X-Iss-3.pdf

[44kgk1lkf6u]

I never worked with things of such precision.  So please bear with me.

What is the oil for?

When the bare copper wires and lugs were mentioned earlier, how are they better than solid twisted pair Ethernet cables with no lugs?

[Vince]

The 500mA fuse has a very unusual form factor as you can see. Looks like a soldered / leaded yellow plastic capacitor or something.

Littelfuse and Bussmann are notorious makers.

https://www.littelfuse.com/products/fuses-overcurrent-protection/fuses/hazardous-area-type-fuses/pico-259

BAS Ex 832302
https://hubbellcdn.com/certificationdoc/TX6363_01-Sira-02ATEX2162X-Iss-3.pdf

Thanks ! It's incredible that these very unusual fuses are still being made, when more common / regular HRC ceramic fuses of appropriate specs, are often unobtainable or, in the rare event that you can find them, are sold at 50 Euros or more a pop...

[Robert763]

The function of the oil is primarily thermal. It keeps the internal parts close the ambiant temerature. For lower resistance values that are tested at higher current it transfers the heat away from the resistance element. The lower value eleents tend to be tube shaped for a large surface area. It also produces a chimney effect to promote convective flow of the oil.  For high resistance like this one it helps improve the insulation resistance and reduce leakage.
In high precision calibrations the whole resitor is placeed in a temperature controlls oil bath. The oil inside the resistor case keeps the actual element close to the oil bath temperature.

[Cyclotron]

Glancing at that thumbnail, I though it was a tequila shot.

Looked like a urine sample to me. You always have to make sure your resistor standards are healthy. Don't want any urinary tract infections.

[m k]

OT
mineral vs. synthetic oil.
Both are the same thing.
When oil is distilled it's mineral oil.
When some of those distilled components are mixed back its synthetic oil.

Generally everything degrades over time, hydro-carbon chains are no different.

Back in the day Citroen had LHM hydraulic oil.
It was said not to be hygroscopic, but was still ordered to change after some years of use.
Later it was replaced with LDS that doesn't need changing, only adding.

Maybe it's sealants and not oil first.
Don't know how it is now but earlier it was so that LDS was not for LHM machines.

[Vince]

     UK SPECIAL   





Just found this ad in my daily leboncoin.fr search, a piece of TE that's out of the ordinary for sure, caught my eye / interest :

https://www.leboncoin.fr/ad/bricolage/3108084806

The ad gives some information / history on the thing.

It's called " VELA ", standing for " Versatile Laboratory Aid " later renamed " Versatile Laboratory Instrument ".
It was designed by Data Harvest for the University of Leeds.
The university used it for educational purposes, to help students do their lab experiments in physics or chemistry.

It was meant to be attached to the then popular / widespread BBC Micro 8 bit computer.
It runs on a 6502 CPU and the EPROM contained a bunch of programs to do various I/O tasks : generate signals or acquire / digitise signals and send that to the BBC micro for analysis.


So, very much a UK special. Did any of our UK friends here, of the BBC micro era,  ever used or knew about this device ?!


Guy wants freaking 200 Euros for it, he is on crack. Plus, I don't have a BBC micro or any 8 bit computer, and not being from the UK, I never used it in school so I have no particular sentimental connection to this instrument...

[Robert763]

Never heard of it. If done for a university it was probably expensive.
There were a multitude of add-ons for the BBC B to do just about anything. Price and quality varied.
I was a big BBC B fan. I used one once to verify the life of a small DPCO relay. We wanted to use it on aircraft and the CAA didn't belive the datasheet life. The user port and a 2N2222A turned the relay on and off and the joystick port measured the contact resistance. One contact was carring current and the other "dry" switching. Every 100 operations the values were recorded. The little relay far exceeded it stated life. A military specfication "aerospace" relay cost fifteen times as much and had a lower quoted life. The CAA got a 4 inch high stack of fanfold test values and we got our modification approved. 

Robert.

[factory]

Never seen one of those before, then again the BBC computers weren't used much in the schools I went to, they had newer machines (Crap'n'tosh) by then, can't remember if the college had any. Only thing I remember being used with a BBC was some kind of primitive robot (the size of a modern robot vacuum cleaner). One of the BBCs was quite vandalised, the keys mixed up & some missing in one room.

I'm not interested in buying it, but for anyone that is, it's probably completely useless without the software & cables, that battery inside is trouble waiting for it to leak, if it hasn't already.

David

[KG7AMV]

Latest Tektronix Surplus Haul.

Tektronix
TSG-130
TSG-271
TSG-170
TSG1001

HP 6634A

I know a long shot on this group but Does anyone have a copy of the Tektronix SDP1000 development software archived? I would like to have it just in case things go south on the TSG1001 TV Signal Generator.
 
I will be doing a tear down of this equipment on my youtube.

[d-el]

Several O-rings arrived. The 25x2.5 mm ones were the best fit.
One of the housings was missing a countersink, which damaged the O-ring. I chamfered it.

[Zephyr]

[snip]
It's called " VELA ", standing for " Versatile Laboratory Aid " later renamed " Versatile Laboratory Instrument ".
It was designed by Data Harvest for the University of Leeds.
The university used it for educational purposes, to help students do their lab experiments in physics or chemistry.

It was meant to be attached to the then popular / widespread BBC Micro 8 bit computer.
It runs on a 6502 CPU and the EPROM contained a bunch of programs to do various I/O tasks : generate signals or acquire / digitise signals and send that to the BBC micro for analysis.

It appears to be very versatile 
Can it do anything as a standalone unit, or is more of just a curiosity piece? If it was a custom made device, and needs a seperate interface or controller, I'm guessing it won't be able to do much on it's own.

I do like those angled face chassis though for building controllers into though.

Bill