Author Topic: T4D #2 - Voltage References, calibration, accuracy, resolution..  (Read 9237 times)

Yttrium

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Hello everyone,

In my opinion, this episode as well as T4D #3 - Metrology, Calibration and the Ultimate Multimeter Check about precision measurements in regards of multimeters and other devices are certainly of some value.

I can think of two main reasons for this, first because the subject is interesting and explores a subject not often covered by other electronics oriented bloggers.  Second, because of the video settings, the more relaxed, less formal environment.

In a world of accelerated time, direct to the point short demonstrations and answers, this format is refreshing.  I like to think of it as the slow food version of video!  Indeed not for everyone, but an important part of the whole.

Finally, as a suggestion for a future video in regards of precision, perhaps some low resistance 4-wire (Kelvin) measurements.  A feature of the soon to come Fluke 8846! :)  Let's see if those new leads really have a resistance of .02 ohm  according to the Fluke 287 (T4D #3, 14:42). ;)

Yttrium  :)
“Logic will get you from A to B. Imagination will take you everywhere.”  Albert Einstein 1879 - 1955

MJLorton

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #1 on: May 08, 2012, 03:28:51 AM »
Hello everyone,

In my opinion, this episode as well as T4D #3 - Metrology, Calibration and the Ultimate Multimeter Check about precision measurements in regards of multimeters and other devices are certainly of some value.

I can think of two main reasons for this, first because the subject is interesting and explores a subject not often covered by other electronics oriented bloggers.  Second, because of the video settings, the more relaxed, less formal environment.

In a world of accelerated time, direct to the point short demonstrations and answers, this format is refreshing.  I like to think of it as the slow food version of video!  Indeed not for everyone, but an important part of the whole.

Finally, as a suggestion for a future video in regards of precision, perhaps some low resistance 4-wire (Kelvin) measurements.  A feature of the soon to come Fluke 8846! :)  Let's see if those new leads really have a resistance of .02 ohm  according to the Fluke 287 (T4D #3, 14:42). ;)

Yttrium  :)
Thanks for that feedback Yttrium.

I know there are many folks who do find that pace too slow but I certainly enjoy it from time to time. I'm glad there are a few that appreciate it :-)

Yes...doing 4-wire measurements will be new to me so I'm keen to see what the results will be. As I mentioned in the last video I posted; I have purchased an old HP 3457A which also does 4-wire measurements  so there could be some interesting comparisons to come.

Cheers,
Martin.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

vredstein

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #2 on: May 09, 2012, 12:34:46 AM »
Hello everyone,

In my opinion, this episode as well as T4D #3 - Metrology, Calibration and the Ultimate Multimeter Check about precision measurements in regards of multimeters and other devices are certainly of some value.

I can think of two main reasons for this, first because the subject is interesting and explores a subject not often covered by other electronics oriented bloggers.  Second, because of the video settings, the more relaxed, less formal environment.

In a world of accelerated time, direct to the point short demonstrations and answers, this format is refreshing.  I like to think of it as the slow food version of video!  Indeed not for everyone, but an important part of the whole.

Finally, as a suggestion for a future video in regards of precision, perhaps some low resistance 4-wire (Kelvin) measurements.  A feature of the soon to come Fluke 8846! :)  Let's see if those new leads really have a resistance of .02 ohm  according to the Fluke 287 (T4D #3, 14:42). ;)

Yttrium  :)
Thanks for that feedback Yttrium.

I know there are many folks who do find that pace too slow but I certainly enjoy it from time to time. I'm glad there are a few that appreciate it :-)

Yes...doing 4-wire measurements will be new to me so I'm keen to see what the results will be. As I mentioned in the last video I posted; I have purchased an old HP 3457A which also does 4-wire measurements  so there could be some interesting comparisons to come.

Cheers,
Martin.

I tried to grasp the concept of 4-wire measurement through the explanation contained on this page
http://www.allaboutcircuits.com/vol_1/chpt_8/9.html
There's something in the concept or at least this explanation of the concept that short circuits my brain. Maybe it's because I can't easily see what's going on with the big arrows and little arrows. I can't see the difference between what this page calls "another pair of wires containing resistance" and just a longer pair of test leads.
Perhaps what's needed is a video featuring a side-by-side comparison of two identical circuits, one using a 2-wire setup, and another using a 4-wire setup. And an enhanced explanation of why "Any voltage dropped across the main current-carrying wires will not be measured by the voltmeter, and so do not factor into the resistance calculation at all."
You up for it?

MJLorton

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #3 on: May 09, 2012, 05:44:23 AM »
Hello everyone,

In my opinion, this episode as well as T4D #3 - Metrology, Calibration and the Ultimate Multimeter Check about precision measurements in regards of multimeters and other devices are certainly of some value.

I can think of two main reasons for this, first because the subject is interesting and explores a subject not often covered by other electronics oriented bloggers.  Second, because of the video settings, the more relaxed, less formal environment.

In a world of accelerated time, direct to the point short demonstrations and answers, this format is refreshing.  I like to think of it as the slow food version of video!  Indeed not for everyone, but an important part of the whole.

Finally, as a suggestion for a future video in regards of precision, perhaps some low resistance 4-wire (Kelvin) measurements.  A feature of the soon to come Fluke 8846! :)  Let's see if those new leads really have a resistance of .02 ohm  according to the Fluke 287 (T4D #3, 14:42). ;)

Yttrium  :)
Thanks for that feedback Yttrium.

I know there are many folks who do find that pace too slow but I certainly enjoy it from time to time. I'm glad there are a few that appreciate it :-)

Yes...doing 4-wire measurements will be new to me so I'm keen to see what the results will be. As I mentioned in the last video I posted; I have purchased an old HP 3457A which also does 4-wire measurements  so there could be some interesting comparisons to come.

Cheers,
Martin.

I tried to grasp the concept of 4-wire measurement through the explanation contained on this page
http://www.allaboutcircuits.com/vol_1/chpt_8/9.html
There's something in the concept or at least this explanation of the concept that short circuits my brain. Maybe it's because I can't easily see what's going on with the big arrows and little arrows. I can't see the difference between what this page calls "another pair of wires containing resistance" and just a longer pair of test leads.
Perhaps what's needed is a video featuring a side-by-side comparison of two identical circuits, one using a 2-wire setup, and another using a 4-wire setup. And an enhanced explanation of why "Any voltage dropped across the main current-carrying wires will not be measured by the voltmeter, and so do not factor into the resistance calculation at all."
You up for it?
Always up for a challenge...I've added it to my "to do" list. Thanks for posting the suggestion.
Cheers,
Martin.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

FOX

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #4 on: May 11, 2012, 03:52:26 PM »
Hi Martin,

just a reading suggestion about references is the Application Note 82 from Linear Technology. It's about "Understanding and applying Voltage references".
Another Voltage reference you might consider is the LTC6655, very low noise, very stable.
Or if you really want go high end the LTZ1000 would be your referece of choise.

I like your videos keep them going.
A closed Switch should have 0 Ohm or less

MJLorton

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #5 on: May 14, 2012, 04:20:51 AM »
Hi Martin,

just a reading suggestion about references is the Application Note 82 from Linear Technology. It's about "Understanding and applying Voltage references".
Another Voltage reference you might consider is the LTC6655, very low noise, very stable.
Or if you really want go high end the LTZ1000 would be your referece of choise.

I like your videos keep them going.

Hello Fox,

Very, very nice references....the datasheet for the LTC6655 gave some interesting info on supporting capacitors so that was handy.

I search searched the South African RS Components site and they don't seem to stock either packages....I'll keep these in mind once I've managed to implement the references I have in my hands at the moment.

Thanks again for posting this info.

Cheers,
Martin.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

olli

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #6 on: August 29, 2012, 01:59:54 PM »
Hello Martin,

First i like your Videos because you explain all in easy words. I am a Hobby Engineer an intrested in Music electronic, but also in Voltage Standards an Measurement Equipment. Maybe you can get the LTC 6655 as a sample from the linear Website. The LTZ1000A is the state of the art Reference but it is very hard to get. The circuit around it needs very low TC resistors and a good PCB layout. Becaus i only have a 4,5 Digit Handmultimeter i want to build the DC NUll Voltmeter from Conrad Hoffmanns Website http://conradhoffman.com/mini_metro_lab.html  Part 2 so i can make a long time Measurement with 3 References (lt 1019 with 2,5 Volts)

Greetz from Germany

Olli
« Last Edit: August 30, 2012, 07:48:03 AM by olli »

MJLorton

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #7 on: August 30, 2012, 03:07:35 AM »
Hello Olli,

Thanks very much for the feedback.

I managed to get the LTZ1000CH but have not tested it yet. I did read about the circuit layout and the challenges one needs to take into account to ensure it functions as a good reference. I'm hoping to receive another LT package as a sample through the local agents so if that goes well I'll try get the LTC 6655 as well.

Your link does not seem to go directly to the DC Null Voltmeter and I could not see it on the page....perhaps I need to wash the sleep out of my eyes?

Cheers, Martin.
Play, discover, learn and enjoy! (and don't be scared to make mistakes along the way!)

olli

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #8 on: August 30, 2012, 07:51:56 AM »
Hi Martin,

i have corected the link to http://conradhoffman.com/mini_metro_lab.html part 2.
Part 1 is reference standard and part 3 is 6 decade kelvin Varley divider.


Greetz from Germany


Olli

SeanB

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #9 on: August 30, 2012, 12:25:58 PM »
I built a simple one with an AD 590 (?) 10.000V unit, and it is good to check and calibrate all the multimeters I have, and to cheack at least at one spot across the ranges. Would love to compare it against a better standard, perhaps next month when I do my pilgrimage to SANAS to get masspieces certified. Will take it along and see if i can wangle a quick check against them if they have a 6 digit meter or a reference source there now. Range of masses they can do are impressive, biggest thing they calibrate are rail weighbridges. Impressive to see a 20 ton steel masspiece that is accurate to the 100g mark. Big strong floor there definitely. Lovely little museum in the lobby as well.

MJLorton

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #10 on: August 31, 2012, 09:13:23 AM »
SeanB...sounds fascinating...are you able to take photos?
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SeanB

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #11 on: August 31, 2012, 10:57:03 AM »
Checked - Ad581, 10.000V reference. May be able to get photos, depends on how they feel, but will take the camera anyway and ask. They are a pretty much nice set, they were hived out of the SA Bureau of Standards into a QUANGO now known as NRCS.

Kiriakos GR

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Re: T4D #2 - Voltage References, calibration, accuracy, resolution..
« Reply #12 on: August 31, 2012, 02:33:35 PM »
This topic acts as a teaser to me especially those days that I am exploring the Agilent portable calibrator.  :)

I will add one teaser photo so to trigger your imagination. :P LOL
Yes this calibrator as volt meter looks 12 counts out, but it is three years old too ( production date) .