Products > Test Equipment
Easy way to test the calibration of a DMM (Fluke 45)?
Fungus:
--- Quote from: J-R on April 04, 2024, 03:56:56 am ---Quite an incredible stance. You are OK with people adjusting their previously factory calibrated test equipment with some random reference? I think you should reconsider your position.
--- End quote ---
The sort of person who would do that deserves to do it.
tggzzz:
--- Quote from: shabaz on April 04, 2024, 04:32:49 am ---
--- Quote from: J-R on April 04, 2024, 03:56:56 am ---What about all the threads here for hacking the Agilent/Keysight scopes (one over 131 pages long)? No need for any West/East nonsense... People will hack equipment in their possession for various reasons and it has nothing to do with where they or the equipment came from. You're moving the goalposts now...
--- End quote ---
No I didn't, except perhaps in the most minor of ways. You were the one that stated that buying from AliExpress means frequently contributing to scammers. I merely responded. But, now you mention Keysight, you think it makes it any better that the scammers that I mentioned in return, are perfectly willing to do the same to fellow colleagues in our own countries too?
--- Quote from: J-R on April 04, 2024, 03:56:56 am ---Quite an incredible stance. You are OK with people adjusting their previously factory calibrated test equipment with some random reference? I think you should reconsider your position.
--- End quote ---
I'm perfectly OK with what I stated. Not my problem if you misinterpret. The text is there forever, and anyone can read it to judge for themselves.
--- End quote ---
Yes, the text is there - but you have snipped the context so a new reader has to actively search out the text. Snipping too much of a conversation is a technique frequently used by those that use dodgy debating tactics, e.g. strawman arguments, moving goalposts, ignoring valid counter-arguments, etc. This isn't stackexchange or EDABoard; multi-level quoting is encouraged.
IMHO J-R comes out of this discussion better than you do.
shapirus:
--- Quote from: mawyatt on April 04, 2024, 02:39:18 am ---You could see the Grid "Speed Up" at night/early morning and the "Dip" mid day when viewing the instruments chart recorder output over a 24 hours period.
--- End quote ---
You have just boosted my motivation to finally implement visualization for the frequency data that I'm already collecting with my homemade mains voltage data logger. I plot voltage (which btw is not even remotely suitable to check the accuracy of any voltmeter), but not frequency, yet.
tggzzz:
--- Quote from: shapirus on April 04, 2024, 10:08:32 am ---
--- Quote from: mawyatt on April 04, 2024, 02:39:18 am ---You could see the Grid "Speed Up" at night/early morning and the "Dip" mid day when viewing the instruments chart recorder output over a 24 hours period.
--- End quote ---
You have just boosted my motivation to finally implement visualization for the frequency data that I'm already collecting with my homemade mains voltage data logger. I plot voltage (which btw is not even remotely suitable to check the accuracy of any voltmeter), but not frequency, yet.
--- End quote ---
In the UK you could compare that with stats from official sources: http://gridwatch.templar.co.uk/download.php
(Great information, but appalling skeuomorphic GUI: click "white none" then click "white voltage" and "white frequency" and select the dates and times.)
shabaz:
--- Quote from: tggzzz on April 04, 2024, 08:37:54 am ---
--- Quote from: shabaz on April 04, 2024, 04:32:49 am ---
--- Quote from: J-R on April 04, 2024, 03:56:56 am ---What about all the threads here for hacking the Agilent/Keysight scopes (one over 131 pages long)? No need for any West/East nonsense... People will hack equipment in their possession for various reasons and it has nothing to do with where they or the equipment came from. You're moving the goalposts now...
--- End quote ---
No I didn't, except perhaps in the most minor of ways. You were the one that stated that buying from AliExpress means frequently contributing to scammers. I merely responded. But, now you mention Keysight, you think it makes it any better that the scammers that I mentioned in return, are perfectly willing to do the same to fellow colleagues in our own countries too?
--- Quote from: J-R on April 04, 2024, 03:56:56 am ---Quite an incredible stance. You are OK with people adjusting their previously factory calibrated test equipment with some random reference? I think you should reconsider your position.
--- End quote ---
I'm perfectly OK with what I stated. Not my problem if you misinterpret. The text is there forever, and anyone can read it to judge for themselves.
--- End quote ---
Yes, the text is there - but you have snipped the context so a new reader has to actively search out the text. Snipping too much of a conversation is a technique frequently used by those that use dodgy debating tactics, e.g. strawman arguments, moving goalposts, ignoring valid counter-arguments, etc. This isn't stackexchange or EDABoard; multi-level quoting is encouraged.
IMHO J-R comes out of this discussion better than you do.
--- End quote ---
I might try multi-level quoting in the future, to see if it is helps. Others (like me) may well prefer not to see repeated walls of text nested. You can't please everyone.
It's up to the reader if they wish to read previous comments or to step in part-way. I've been speedy with the responses so one doesn't need to traverse too far back. Anyone freshly googling how to test their calibration will easily be able to see the discussion around various options. It's not a difficult discussion to follow. If anyone is really stuck, I'm happy to clarify my comments at least.
My contribution started on page 2, with the following entire text:
--- Quote ---Very kind, generous offer to unofficially calibrate.
Just to put some sample numbers out there, for the AD584 cheap references (sub-$10 on AliExpress), by chance, a friend and I have both measured these devices (one sample each, purchased separately at different times) using two separate DMM6500 meters.
The label on it, claiming to have been measured with HP 3458A, is, of course, completely untrue (unless it's a completely broken HP 3458A!). They probably used (at best) a 6.5-digit meter, perhaps not even calibrated, and even then, they have typos in the printed values (the label on mine had a noticeably erroneous extra digit for one of the values!).
However, on the plus side, it turned out that the nominal voltage values (2.5V, 5V, 7.5V, 10V, were actually close enough to the real values, that it's very likely that one would be able to tell if that 0.02V discrepancy you're seeing between multimeters is a problem with one meter or the other, or both. In other words, a 20 mV discrepancy should be identifiable if it's present at one of those four voltages (2.5/5/7.5/10V).
Beyond three digits, you can't really rely on it with no measurement with a known calibrated instrument. Nevertheless, for the price (under $10) with no further measurement, it is a crude finger-in-the-air type of check if absolutely nothing better is available.
Just in case this helps, this was my sample result:
Label My measurement
------- ---------------
2.49954 2.49963
4.999501 4.99964
7.39875 7.49899
9.99823 9.99854
--- End quote ---
My last message in its entirety that you were referring to, which was on page 4:
--- Quote ---Quote from: J-R on Yesterday at 08:26:43 am
It's true that not everyone needs the same level of performance from their test equipment, but these random unknown references really are bad no matter how you look at it. The technical shortcomings have already been well discussed (and perhaps somewhat ignored), but a different point is that you are frequently contributing to people who would be totally fine scamming you wherever possible.
--- Quote ---That works both ways. There's no innocence on either side, with Westerners openly scamming by unlocking functionality that they have not paid for on Eastern test equipment. I don't choose to automatically mistrust every seller based on the occasional bad experience here or there.
--- End quote ---
Quote from: J-R on Yesterday at 08:26:43 am
Instead, send your money to individuals who are not really doing it for the money but for the love of the hobby. Win/win for everyone.
--- Quote ---Not everyone thinks the same. It is possible to "buy local" as well as to help others across the world, who might actually need the money.
--- End quote ---
Quote from: J-R on Yesterday at 08:26:43 am
And again my main point about why these cheap references are "dangerous" is that they have specific voltages printed on them and are sold as "references" so buyers apply additional weight to them. What ratio of buyers do we think have adjusted their DMM based on the "reference" compared to adjusting the "reference" based on their DMM?
--- Quote ---Let's guess at an extreme 90% of buyers adjusting their DMMs based on that board. Even if they did, so what? They would have a DMM that was possibly inaccurate by tens of mV at the most? What are the implications:
(a) For a hobbyist, if it affects their projects, it will be a great learning curve on what to trust. If something is worth doing, it's worth doing wrong.
(b) On the other hand, if you're a professional: a qualified engineer may well rely on prototype or 'uncalibrated' equipment when developing products; there's nothing abnormal in that. But equally, that engineer is in every way liable for trusting a $10 device over a calibration if they ignored a process, or were supposed to be working to a standard, or if a body of other professionals would not have done the same for that specific task.
--- End quote ---
--- End quote ---
Not one person in the discussion suggested that it was a good idea to calibrate a test tool with a $10 device. In fact, everyone went out of their way to mention that their suggestions were a spot-check to determine any significant glaring error at best.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version