[defaced thread] Affordable DMM Checkers: AC Reference...

[Majorassburn]

Will Start New Thread Later Without "tggzzz" Bullshit & Interference!

[tggzzz]

I design 'em and build 'em and they REALLY work! 
eBay Links:
https://www.ebay.com/itm/285825801852
https://www.ebay.com/itm/285823822244
https://www.ebay.com/itm/285807578003
https://www.ebay.com/itm/285823885283
Thanx for looking! 

Description states
"LT1236-10 Ultra-Low-Drift 5ppm 10V Reference."
"Final Trim to 10.0000 VDC @ 78F, 50% Humidity"
"NEW, Hand-Crafted in USA to Work PERFECTLY, No Returns."

That's 5ppm per what? Day, month, year, degree C, degree F, supply voltage, RH, shock (since the ICs are socketed)?

Picture below states "Designed to affordably verify the function of Digital Multimeters".
Does that mean it is suitable to verify the function of my Agilent 34410A, Keithley 2015 THD, Solartron 7081?

[coromonadalix]

I would say not ...  while i salute the projects,  they can not compare to well designed lm399  and ltz1000  ones or the AD xxx series too

to check 6.5 digits meters you need more ...

Resistors references   are weak ... say ordinary

[tggzzz]

I would say not ...  while i salute the projects,  they can not compare to well designed lm399  and ltz1000  ones or the AD xxx series too

to check 6.5 digits meters you need more ...

Resistors references   are weak ... say ordinary

"You might think that. I couldn't possibly comment"
https://villains.fandom.com/wiki/Francis_Urquhart

[Kosmic]

I design 'em and build 'em and they REALLY work! 
eBay Links:
https://www.ebay.com/itm/285825801852
https://www.ebay.com/itm/285823822244
https://www.ebay.com/itm/285807578003
https://www.ebay.com/itm/285823885283
Thanx for looking! 

Also, about those "0.05% Precision Resistors" do you know the temperature coefficient ? They look like your generic metal film and could be around 200-100 ppm/C. So even, if they were selected, change in ambient temperature could easily move them outside the 0.05% you are mentioning. I don't think calling them "Precision Resistor" is really accurate.

I don't want to be overly negative but all that look a lot like a modern snake oil salesman. Of course your clients are not going to complain, they are not equipped to validate your claims. I'm not even sure you are.

[Majorassburn]

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[Majorassburn]

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[Majorassburn]

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[tggzzz]

As for the ppm change in resistors, the documentation I include with every device reminds buyers that resistors (and other components) are temperature sensitive and that my specs for accuracy are based upon operation in a stabilized environment with no-draft ambient of 78F and 60% humidity.

Translation: the after-sales literature has sufficient caveats to cover my arse.

[tggzzz]

If you knew anything at all about selling these types of devices on eBay to somewhat unsophisticated buyers (which you obviously have no feel for), you would understand that choking an ad with globs of technical specifications would quickly cause buyers to skip to the next seller's ad.  Achieving a balance of general, parametrically illustrative specifications along with typical and comprehensible application information is about the best a seller can do in the very limited space-time available to encourage a transaction.

And yet your adverts do contain "gobs of technical specifications". And omissions.

In that context, consider Kosmic's earlier post:

...
I don't want to be overly negative but all that look a lot like a modern snake oil salesman. Of course your clients are not going to complain, they are not equipped to validate your claims. I'm not even sure you are.

Therefore, in my ads, I try to present a few technical specs as a reference base to validate the usability and quality of the device and also, present enough application information to help the potential buyer to recognize the intrinsic usefulness of the device and to stimulate the desire to buy one.
...
I have stated many times in this forum and elsewhere, that I do not claim my devices are going to satisfy the perfectionist demands of what they call "volt-nuts" or of those who are silly enough to seek a $20 calibrator that could actually perform well-enough to calibrate a DMM6500 or 34465A, etc.

If you limited the claimed to, for example, "...verify the function of 3.5 digit Digital Multimeters", then the points wouldn't even arise.

What you claim here (or "elsewhere") is irrelevant; what you claim in the advert is what matters.

[Zucca]

https://www.eevblog.com/forum/metrology/affordable-useful-ac-dc-references/

[Majorassburn]

deleted

[watchmaker]

[

If you limited the claimed to, for example, "...verify the function of 3.5 digit Digital Multimeters", then the points wouldn't even arise.

What you claim here (or "elsewhere") is irrelevant; what you claim in the advert is what matters.

This is basic measurement theory. While you need higher resolution than the manufactured reference to measure its calibration error, that same calibration reference can then be used on on lower resolution instruments (assuming it is stable).  If you only work in mA, you do not care what is going in pA.

So a lot depends on claims for where it should be used.  And the reliablity of the maker.

FWIW, I bought one of the current and voltage references from AliExpress.  It includes a sketchy paper claiming the actual values as measured by some reference down to the 7th decimal point.  Turns out these measurements were within a couple counts on my Fluke 45, Fluke 8842, HP 358a and Keysight 1252.

Have no idea why I bought it since all my instruments already agreed, but it was cheap and I am a measurement junkie (work down to 500 micro meters).

[tggzzz]

If you limited the claimed to, for example, "...verify the function of 3.5 digit Digital Multimeters", then the points wouldn't even arise.

What you claim here (or "elsewhere") is irrelevant; what you claim in the advert is what matters.

This is basic measurement theory. While you need higher resolution than the manufactured reference to measure its calibration error, that same calibration reference can then be used on on lower resolution instruments (assuming it is stable).  If you only work in mA, you do not care what is going in pA.

So a lot depends on claims for where it should be used.  And the reliablity of the maker.

FWIW, I bought one of the current and voltage references from AliExpress.  It includes a sketchy paper claiming the actual values as measured by some reference down to the 7th decimal point.  Turns out these measurements were within a couple counts on my Fluke 45, Fluke 8842, HP 358a and Keysight 1252.

Have no idea why I bought it since all my instruments already agreed, but it was cheap and I am a measurement junkie (work down to 500 micro meters).

Yes, repeatedly.

You bought it for fun. The only surprise is the degree of agreement.

But, as you know, it is relatively cheap and easy to get all your instruments to agree with each other. It is much more difficult and expensive to get them to agree with two other people's instruments

[watchmaker]

Yup!!

Interestingly, all my instruments agreed as shipped.  I cannot adjust the HP, the Keysight or the 8842.

This is indicative of "inter rater" reliability;which is a precursor to validity; which in this case would be verification against a standard such as NIST.

As for my uses, I kind of doubt I have time to get far enough along to be concerned with nano amps, let alone pico amps.  I am just starting capacitors and inductors.

I WOULD be very interested to learn where such measurements are used.  I know it is not an issue of "trivial precision".

FWIW, I have come to conclusion that the way to bring the world crashing to its knees is to end capacitors.  Who the hell knew?

Regards,

Dewey

[GigaJoe]

Thaaaat story happened in the past, it continues, and will be.

but ... damn  i missed "ULTRA HIGH PRECISION"  with isolation board .....
and ... honestly .... that board missed sticky copper foil ,  ( i assume, you know what im talking about)

[tatel]

Will Start New Thread Later Without "tggzzz" Bullshit & Interference!

Apparently you still have to grow that thicker skin. Why to open a new thread? Do you think there won't be people calling out your over-hyped shit?

Description states
"LT1236-10 Ultra-Low-Drift 5ppm 10V Reference."
"Final Trim to 10.0000 VDC @ 78F, 50% Humidity"
"NEW, Hand-Crafted in USA to Work PERFECTLY, No Returns."

That's 5ppm per what? Day, month, year, degree C, degree F, supply voltage, RH, shock (since the ICs are socketed)?

Picture below states "Designed to affordably verify the function of Digital Multimeters".
Does that mean it is suitable to verify the function of my Agilent 34410A, Keithley 2015 THD, Solartron 7081?

This ^^^ is over-hyping.

Even worse, if you have to use that "Made in USA" as a sales argument, you are obviously a scammer. Homeland is the last refuge of scoundrels.

If you are so confident your shit works PERFECTLY, you should accept returns OF COURSE.

Also, about those "0.05% Precision Resistors" do you know the temperature coefficient ? They look like your generic metal film and could be around 200-100 ppm/C. So even, if they were selected, change in ambient temperature could easily move them outside the 0.05% you are mentioning. I don't think calling them "Precision Resistor" is really accurate.

I don't want to be overly negative but all that look a lot like a modern snake oil salesman. Of course your clients are not going to complain, they are not equipped to validate your claims. I'm not even sure you are.

+1

I think you should be banned. You are evidently using this forum to promote your sales. But the worse is, you are too much aggressive.  If you can't take the very justified critics you receive, please go away. We don't need your burning ass here. Go care for your hemorrhoids elsewhere.

[abeyer]

Will Start New Thread Later Without "tggzzz" Bullshit & Interference!

This looks a lot like "Will delete history and repost to try to avoid genuine critique and sidestep the rule about not flogging products."

(That said, both parties have been behaving poorly and letting their shit-flinging spill out into unrelated threads... so a mod hammer on both might be called for.)

[quince]

The confusing parts here are entirely market based

Who buys a voltage reference for $20 on eBay?

What kind of person who needs a high precision voltage reference would spend $20 when they have a $500 budget?

Why would you promote a $20 voltage reference to a crowd of engineers who have $1,000-$100,000 of equipment sitting in their shed, who would be willing to spend $6000 if it meant getting another 2 digits of precision?

Why would you design a product for a market that doesn't exist?

There's plenty of room in the market for products where the schematic is public but the board files are private. You charge some mark-up on the cost of components+assembly, do some QC, and offer group buys to interested parties who would rather not build it. Skip the eBay fees, et cetera. Alternatively, save yourself the assembly cost and sell the parts kit at a discount. You make your money on the distribution+convenience+layout.

Small shops can make 50-80% gross margin on small-run products like this when they price them right.

No point going to the effort of assembling such a low-volume, low-cost, outdated product yourself with perfboard and then not even sharing the schematics.

[tggzzz]

And that, ladies and gentlemen, is a good example of why it is worth quoting someone rather than merely replying to their posts.

It avoids the problems that lead to the sardonic joke common amongst Soviet citizens when I was young (and probably since then too): students of Soviet history know how difficult it is to foretell Soviet history.

I wonder whether ebay seller sqwarrel will continue to sell the devices https://www.ebay.com/usr/sqwarrel

[coromonadalix]

well

I do salute some projects like this,  but there was a few wording / sentence / specs   etc ...    who did not make sense at all 

You have to be very careful on what you write or assume or display with great enthusiasm  ....

that's all  for me if you stay in the non professional segment ...

but if you assume better than that ... you have to be prepared and show / prove what you meant by x  or that x   ...

[tatel]

I wonder whether ebay seller sqwarrel will continue to sell the devices https://www.ebay.com/usr/sqwarrel

The listings he linked in this thread have been ended on Tue, April 23, but not those in the link you just provided. Well, I don't really care. A pity, but this guy obviously needs professional help. Not speaking about EE.

[wraper]

I wonder what logic was behind making these on a protoboard. Ordering custom PCBs is cheaper and 10x faster to assemble. Not to say look way more professional. Who in hell does this unless needs a few pieces at most and on the same day. That's beside other nonsenses with these.

[Zucca]

It's not because of "tggzzz"... 

[pcprogrammer]

 

High precision voltage reference, but you need to calibrate it first using the potentiometers on the prototype board. 

For 56 bucks delivered on my doorstep, I can make it myself and maybe even make something better.

You can't blame the guy for trying though. Unfortunately for him he came here to meet his doom.