EEVblog #544 - Fluke 5450A Resistance Calibrator Teardown

[EEVblog]

What's inside a vintage Fluke 5450A Resistance Calibrator used in cal labs to calibrate multimeters?
Coto reed relay: http://www.farnell.com/datasheets/1486738.pdf
High Resistance measurement with a relay matrix:

[daddario]

I've always found precision resistors absolutely fascinating.
When I first opened up my Cambridge Instrument co. 5 'digit' decade box for cleaning, I've must have spent at least half an hour just examining all the hand-wound resistors and the stupendous switches in it. No painting or piece of architecture can match up the beauty and and the art of these things. Amazing.

[sipo75]

I stumbled upon the Fluke 5450A only last  week on eBay and was tempted to buy one. But they are still on the high side for transatlantic shipping.

As usual a great teardown.

[Vgkid]

What a great teardown. I love seeing precision resistors in test gear. It will be interesting if this video drives up prices. If I was rich I could have bought one over the summer, but I bought a broken multimeter instead.

[Dave]

Yep, Sprague are definitely still around. Does Vishay Sprague ring any bells?

Great video, mate. I really love precision test gear, be it old or young.

[EEVblog]

Does anyone else a see an ad below the embedded youtube video above?
I've never seen that before. I don't know if that's youtube or the forum plugin?

[jebcom]

Does anyone else a see an ad below the embedded youtube video above?
I've never seen that before. I don't know if that's youtube or the forum plugin?

I don't see an ad below it. A small Fluke ad showed up at the bottom of the video itself briefly, but that's common.

[Scutarius]

No ads, with and without adblock.

[V42bis]

I wonder if they just get as close as they can first time on the low value wire wound 1 ohm or if there is a tweek while building them. It would be impossible to get the right wire length first time.

Great work Dave

[EEVblog]

Here is what I mean

[Orpheus]

It occurs to me that by feeding the wire through a conductive guide or nozzle, they could measure its resistance AS it was wound. No guesswork needed.

[BravoV]

No embedded ads here at my Chrome at my PC, and also Safari and Chrome at ipad.

Example from my Chrome at PC :

[Vgkid]

No embedded ads on IE either.

[Treehouseman]

Here is what I mean

Dave, I'm afraid you need to check your PC for an infection. I noticed some text overlaid on the bottom of the player and it said "Deal Finder". After looking it up, came across this (http://www.bleepingcomputer.com/forums/t/497925/removal-of-deal-finder-malware/) where someone posted an image of it that the ad looks very similar to yours. There should be info on how to remove it there, if there isn't sufficient information or the method listed doesn't work I'll see if I can dig something else up.

[NiHaoMike]

Why aren't the resistors mounted inside a thermal oven to reduce the effect of ambient temperature and sealed in a hermetic chamber with desiccant to prevent humidity from changing the values?

[Kryoclasm]

Those 1 ohm and 1.9 ohm resistors look like they are wrapped on mica sheets

I'm betting those cost a very pretty penny each.




Wiki snippet about Mica Sheets...
These sheets are chemically inert, dielectric, elastic, flexible, hydrophilic, insulating, lightweight, platy, reflective, refractive, resilient, and range in opacity from transparent to opaque. Mica is stable when exposed to electricity, light, moisture, and extreme temperatures. It has superior electrical properties as an insulator and as a dielectric, and can support an electrostatic field while dissipating minimal energy in the form of heat; it can be split very thin (0.025 to 0.125 millimeters or thinner) while maintaining its electrical properties, has a high dielectric breakdown, is thermally stable to 500 °C, and is resistant to corona discharge.

Sheet mica is used in electrical components, electronics, isinglass, and atomic force microscopy.

[acstd90]

The 1 and 1.9 ohm resistors are mounted on Mica card
The % for the resistors and the nominal value is a specification for the actual resistance value around the nominal cardinal value. The actual specification of the resitance used for calibration purposes is the absolute specification and the TC specification. The ppm / % is used in the entry mode. The entry mode is to enter the value seen on the meter under test and the 5450 will reply with the difference of the device under test with respect to the standard in ppm or %. Relays on the sockets allow for ease of replacement but they also keep heat from the coil farther away from the PCB that has the resistors mounted on it. Same with the regulator mounted on the flex strip.

[kaushleshchandel]

Does anyone else a see an ad below the embedded youtube video above?
I've never seen that before. I don't know if that's youtube or the forum plugin?

I don't see any ads either.. Only links to your own videos...

[alm]

I agree that this looks like Spyware/Adware on Dave's computer.

[Lightages]

It looks to me that the regulator that is connected to the board with that flat flex cable was to thermally isolate it from the rest of the circuit. I think it is obvious why one would do that.

[BravoV]

Really surprising to see that new "branded"  benchtop DMM just can't do auto ranging decently, isn't that strange ? 

[calexanian]

Potter and Brumfield relays have been around since Moby Dick was a guppy, Guardian relays are just about as old. Also that does appear to be mica in those low value resistors, You never forget that broken edge appearance. The reason for the sockets on those relays was multi fold. First it was unheard of and frowned upon to directly solder those relays as many of them used polystyrene in the casing for low leakage and it would melt when soldered quite easily. Also I recall people would be nervous about the limited switching life numbers for those relays. Some of the various platings had ridiculously  low cycle counts before replacement like 10,000 times, particularly for gold plating which these most likely are. Somewhere I have a bucket of those things from our OLD products and I used to play with them when I was a kid. Then one day we started buying PC mount relays from Hasco (And still do 30 years later) Those appear to be Micalex or Micanol plastic in those sockets, fancy fancy expensive mil spec. Its typically that mint green color.

[alm]

Really surprising to see that new "branded"  benchtop DMM just can't do auto ranging decently, isn't that strange ? 

No. What's the problem? Any decent autoranging system will be designed with some hysteresis to prevent the meter from nervously switching between two ranges. In general a stable reading with one digit less is preferable to the meter switching range every few seconds due to noise. If you want to force the meter to choose one particular range, use manual ranging. Calibration procedures will always call for manual ranging.

[ddrl46]

Here is what I mean

I've had that happen before, some shitty extensions in Google Chrome (I assume you are using Google Chrome as well) add that under images / videos. Try disabling all your extensions and enabling them one by one to figure out which one is causing it. A virus scan probably isn't a bad idea either.

If I remember correctly that deal finder thing is called Superfish.

[Stonent]

Those 1 ohm and 1.9 ohm resistors look like they are wrapped on mica sheets

I'm betting those cost a very pretty penny each.




Wiki snippet about Mica Sheets...
These sheets are chemically inert, dielectric, elastic, flexible, hydrophilic, insulating, lightweight, platy, reflective, refractive, resilient, and range in opacity from transparent to opaque. Mica is stable when exposed to electricity, light, moisture, and extreme temperatures. It has superior electrical properties as an insulator and as a dielectric, and can support an electrostatic field while dissipating minimal energy in the form of heat; it can be split very thin (0.025 to 0.125 millimeters or thinner) while maintaining its electrical properties, has a high dielectric breakdown, is thermally stable to 500 °C, and is resistant to corona discharge.

Sheet mica is used in electrical components, electronics, isinglass, and atomic force microscopy.

Mica is one of the few materials that can provide a physical barrier, yet allow alpha radiation through. It's pretty much the exclusive material used in high sensitivity geiger probes.