Author Topic: KickStarter: High Accuracy Programmable & Cute Resistance Substitution Box  (Read 5202 times)

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Offline Tigerwoods

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Quote
I repeat...
Why do you want to see results from out-of-calibration equipment?

Such equipment might have rich experience, that's why I want to learn from it.

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What value would it add to your claims and/or your device?

NOTHING for my claims & device. Instead, I might adding one gentleman‘s name to my friends' list.
« Last Edit: July 20, 2022, 03:48:34 pm by Tigerwoods »
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Offline free_electron

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since " IET says "the OS-260 residual resistance is automatically factored out in output resistance value".

wouldn't it be easier to specify
1) the residual resistance of your device. this would satisfy the request from people to know what this value is.
2) display the SET value , except for 0ohms

let me explain 2:
i SET 100 ohms. The device knows its residual is 0.23 ohms (established during the calibration) , so the device programs the internal resistor array to 99.77 ohms so that you will measure 100 ohms at the terminals (which is what we have asked from the device). So it displays 100 ohms and we will measure 100 ohms. The residual has been taken into account, no need for user calculations.

Since the device knows its residual (stored in eeprom during calibration ) you cannot enter a value lower than the residual. it will refuse a request to set 0. if you enter any number lower than, or equal to the residual the display shows the residual value and/ or the text -LIMIT-

How's that for a solution ?

- your are not hiding anything
- what i request is what i get at the terminals
- if the residual drifts it can be calibrated away.
- no user calculations needed.

you could even store the contact resistance for every relay (assuming they don't drift) so you can compensate the chain for whatever request you have.
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Any comments, or points of view expressed, are my own and not endorsed , induced or compensated by my employer(s).
 
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Offline tggzzz

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I repeat...
Why do you want to see results from out-of-calibration equipment?

Such equipment might have rich experience, that's why I want to learn from it.

If you want a "rich experience", then I suggest trying a flight in a glider, or having a "tasting meal" at a 3* Michelin restaurant, or learning to align your chakra with you reiki.

You say "1.30" but I say "1.31" cannot lead to anything useful.

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Quote
What value would it add to your claims and/or your device?

NOTHING for my claims & device. Instead, I might adding one gentleman‘s name to my friends' list.

I accept that your culture and language differ from mine.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline Tigerwoods

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Thank you so much for your help to explain.

But I'm afraid we sometimes mixed up "residual" and "offset of the range".

For the traditional resistance box, the function of residual is used for describing the accuracy in the format like "±(n% + residual)" - "n%" is for base resistors while “residual” is for internal wires, switches and terminals.

As for the output range, it's ture for traditional resistance box that in general "residual" equals to "offset of the range".

While for QR10 and OS-260, we don't need "residual" to participate in the description of the accuracy, since we just treat base resistors, internal wires, switches and terminals "equally". So we just say the accuracy is "±n%".

As for the output range, for example, say QR10 is 1 Ω-1.2 MΩ. You might still insist 1 Ω is the residual, but I would say 1 Ω is just the offset of the range. Since if this 1 Ω is residual, then the description of QR10 accuracy should be ±(n% + 1 Ω) - however, accuracy description like this is incorrect for QR10.

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How's that for a solution ?

- your are not hiding anything
- what i request is what i get at the terminals
- if the residual drifts it can be calibrated away.
- no user calculations needed.

Cannot agree more. Honestly, I NEVER though this could be an "event".
To say the least, for QR10, will there be any loss of advantage if we just delete that row on the comparison table?
« Last Edit: July 20, 2022, 06:26:19 pm by Tigerwoods »
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Offline Magnum

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I am just a hobbyist and newbie, so that might be the problem why I don't understand the discussion:

I set a value on the device, it tries to set the output as close as possible and tells me the actual (calibrated) output value. I don't have to care about residual resistance. IMHO everything is fine.

The only thing that matters for me is the TC, aging of the resistors and if the relays degrade over time. TC is stated, I don't know if resistors normally change their values over time. Maybe humidity might be a problem? If I understand it correctly, to get the lowest resistance all relays need to be closed. Is it possible to close all relays manually and just measure the resistance? That would be an easy way to see if the contact resistance of the relays changes as an indication for recalibration / relay maintenance.
 
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Offline Tigerwoods

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Hi,
Quote
I set a value on the device, it tries to set the output as close as possible and tells me the actual (calibrated) output value. I don't have to care about residual resistance. IMHO everything is fine.
Great.

Quote
The only thing that matters for me is the TC, aging of the resistors and if the relays degrade over time. TC is stated, I don't know if resistors normally change their values over time. Maybe humidity might be a problem?
1) TC is ok, in general it's much lower for most points (since different base resistors that with opposite slope can cancel each other on TC).
2) Aging is depending on your actual application. If only for light load application, Vishay 0204 MELF resistor is not that ”fragile“, especially for <=25 ppm grade.
For resistor, in general, the longer you use, the more stable it will be.
Anyway, NEVER overestimate such "general purpose" tool as "resistance standard", since they major in different fields.
3) As for humidity influence, to my experience it can be ignored since QR10 is almost sealed (Just remember don't let water/dews in). But for > 1MΩ output measurement, be careful for humidity, EMF, Electrostatic and even parasitic capacitance of the cables.

Quote
If I understand it correctly, to get the lowest resistance all relays need to be closed. Is it possible to close all relays manually and just measure the resistance? That would be an easy way to see if the contact resistance of the relays changes as an indication for recalibration / relay maintenance.
That's a very good idea. :-+
Just press key "0" and then press key "OK" to confirm.


« Last Edit: July 21, 2022, 04:26:44 pm by Tigerwoods »
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Offline tggzzz

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Hi,
Quote
I set a value on the device, it tries to set the output as close as possible and tells me the actual (calibrated) output value. I don't have to care about residual resistance. IMHO everything is fine.
Great.

Quote
The only thing that matters for me is the TC, aging of the resistors and if the relays degrade over time. TC is stated, I don't know if resistors normally change their values over time. Maybe humidity might be a problem?
1) TC is ok, in general it's much lower for most points (since different base resistors that with opposite slope can cancel each other on TC).

That statement is wishful and too optimistic: TCs can just as easily add.
Resistors from the same batch tend to have the same characteristics, and will tend to add.

If there are design characteristics that ensure cancellation, then let's hear what they are.

You won't have enough independent resistors in series at any one time for there to be a statistically useful chance the overall TC will be smaller.

Quote
2) Aging is depending on your actual application. If only for light load application, Vishay 0204 MELF resistor is not that ”fragile“, especially for <=25 ppm grade.
For resistor, in general, the longer you use, the more stable it will be.
Anyway, NEVER overestimate such "general purpose" tool as "resistance standard", since they major in different fields.
3) As for humidity influence, to my experience it can be ignored since QR10 is almost sealed

Almost sealed is not sealed. Over the years changes in atmospheric air pressure will force air in and out of your device, and that will take moisture in and out.

Quote
(Just remember don't let water/dews in).

In a sealed device, the internal humidity can easily reach 100%, with condensation. All that is needed is for the device to be transported or stored at a lower temperature than when it was manufactured. Start by thinking of the temperature of an aircraft's cargo hold. Then consider storage in a loft or unheated room.

Hence, unless you tell us the temperature and humidity when your device was manufactured, we cannot assess whether condensation will have occurred before it reaches us or while stored with us.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline Magnum

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I will give it a try. So I can check it out and don't have to speculate how it performs.
Now I just have to wait until December...
 
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Offline tggzzz

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I will give it a try. So I can check it out and don't have to speculate how it performs.
Now I just have to wait until December...

... how your one performs by testing.

Without knowing what is defined by design, another one might perform very differently.

One of the main USPs of HP test equipment was that it "just worked as advertised". Indeed, Paul Ely was the recipient of a famous memo from Dave Packard when a computer did not perform as advertised. Ely framed the memo, hung it on his wall, it became a "Bill and Dave" story, and Ely had a good career in HP because he did The Right Things.

I hope the example you receive satisfies your requirements :)
« Last Edit: July 21, 2022, 10:53:51 pm by tggzzz »
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline Tigerwoods

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I will give it a try. So I can check it out and don't have to speculate how it performs.
Now I just have to wait until December...
Thanks man, for your trust and open. I already see your order and we'll try our best to get it done ahead of schedule.
I love peace, alright let's fight.
 

Online ledtester

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Re: KickStarter: High Accuracy Programmable & Cute Resistance Substitution Box
« Reply #60 on: September 14, 2022, 09:40:39 pm »
I happened to run across a similar product -- the "OhmStar" made by Labmetric:

https://www.labmetric.com/specifications

and here's a short demo video:

Ohm star RTD Promo
https://youtu.be/z8Q-UG3CGSg

An ebay listing:

https://www.ebay.com/itm/253114984571

During the video the device seems to be making bursts of clicking sounds - probably from relays.
 


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