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Using Arduino => Project Guidance => Topic started by: jean507 on Jan 21, 2013, 01:32 am

Title: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 01:32 am
Hi,

My goal is to measure a very fine wire with 10 µm (or better) precision using the arduino. I've been looking around for a way to do this and I could not find anything other than laser micrometer. (i.e. http://www.micro-epsilon.com/optical-micrometer/micrometer/optoCONTROL_1200/index.html (http://www.micro-epsilon.com/optical-micrometer/micrometer/optoCONTROL_1200/index.html))

Is anyone familiar with a strategy/way to achieve this in a DIY fashion using the arduino. What kind of sensors would you need?

Thank you

Boots
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: johnwasser on Jan 21, 2013, 01:41 am
It might help if you give an actual dimension for  "very fine wire". 

I'm guessing you are measuring the width of the wire.  Is that true?

How frequently do you need to make the measurement?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: dhenry on Jan 21, 2013, 01:50 am
one approach would be to use the wire to set the gap between two metal plates and measure the capacitance between them.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: PeterH on Jan 21, 2013, 01:57 am

My goal is to measure a very fine wire with 10 µm (or better) precision using the arduino.


Have you considered using a microscope?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: gardner on Jan 21, 2013, 02:24 am
Perhaps measure the resistance of a known length of wire, and correlate to cross-sectional area and thereby diameter.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 04:30 am

It might help if you give an actual dimension for  "very fine wire". 

I'm guessing you are measuring the width of the wire.  Is that true?

How frequently do you need to make the measurement?


Thanks for the reply.

I am talking about a wire of AWG44 around 0.0585 mm in diameter.

Yes, I am measuring the width/diameter of the wire and I would like to make the measurement several time per seconds using the Arduino.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 04:32 am


My goal is to measure a very fine wire with 10 µm (or better) precision using the arduino.


Have you considered using a microscope?


Thanks for the reply.

Yes, but I need to take the measurement automatically and several times per seconds.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 04:34 am

one approach would be to use the wire to set the gap between two metal plates and measure the capacitance between them.



Thanks for the reply.

I am not familiar with this approach. Would you have some examples or perhaps reading on that technique of wire diameter measurement.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: rvasque on Jan 21, 2013, 04:38 am
Are you serious?
You need to be able to distinguish .001mm precision?

What are you doing?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 04:46 am

Are you serious?
You need to be able to distinguish .001mm precision?

What are you doing?


Hi,

10 micrometers = 0.01 millimeters
AWG44 is finest wire gage I would like to be able to measure. I'm trying to read the diameter of the said wire as it unwinds from its spool.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: rvasque on Jan 21, 2013, 04:59 am
I'm thinking 1micron... but still, 0.01mm resolution?

And what's your contraption/Arduino supposed to do when you detect a delta change of 0.01mm in the wire diameter?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 05:02 am
I am interested in tightly spooling the wire on a coil former. The coil will then be used for another project and it has to be well packed. Instead of working form the theorical diameter of the wire when making the coil, I am interested in measuring it as it unwinds from it's original spool (more accurate).
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: zoomkat on Jan 21, 2013, 05:26 am
Quote
Is anyone familiar with a strategy/way to achieve this in a DIY fashion using the arduino. What kind of sensors would you need?


The arduino and its limitations are fairly well understood. The sensor you seek will be the challange. kind of like wanting to use an arduino to turn an empty pizza box into a flat screen tv.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: JimboZA on Jan 21, 2013, 05:30 am
Quote
measure a very fine wire with 10 µm (or better) precision


But how accurate do you want it?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 05:32 am

Quote
measure a very fine wire with 10 µm (or better) precision


But how accurate do you want it?


I would be really happy if I could record the wire diameter within 0.001mm. I'm not sure if that is possible.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: rvasque on Jan 21, 2013, 05:39 am
Quote
I am interested in tightly spooling the wire on a coil former. The coil will then be used for another project and it has to be well packed. Instead of working form the theorical diameter of the wire when making the coil, I am interested in measuring it as it unwinds from it's original spool (more accurate).

So you're trying to wind inductors? Are these audio inductors?

I'm just thinking, who cares about the EXACT diameter of your wire (and whatever 0.01mm variations it has)... it's more important to get the correct inductance and DCR (within % tolerance) of your limited equipment? .... rather than worrying about it's diameter?

Maybe build an inductance meter using an Arduino (very possible, with high accuracy) and have your machine keep winding until the set inductance value is reached -- regardless of your wire diameter variations.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: JimboZA on Jan 21, 2013, 05:43 am
This (http://en.wikipedia.org/wiki/File:Accuracy_and_precision.svg) is a nice diagram explaining the difference between accuracy and precision
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 05:57 am

This (http://en.wikipedia.org/wiki/File:Accuracy_and_precision.svg) is a nice diagram explaining the difference between accuracy and precision


Yes I understand. I would like to know if there is a technique that would maximize both accuracy and precision when dealing with a wire and target resolution of 0.001 mm.

Any thoughts?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: johnwasser on Jan 21, 2013, 02:23 pm
If I wanted to wind a coil with maximum packing density (like for a Tesla coil secondary) I would just have the feed carriage lag a little behind so that the new wire is pressed lightly against the previous turn.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: PeterH on Jan 21, 2013, 02:26 pm

Instead of working form the theorical diameter of the wire when making the coil, I am interested in measuring it as it unwinds from it's original spool (more accurate).


I'm skeptical that your measurement accuracy would be better than the manufacturing accuracy. Have you measured the actual thickness, and does it vary (between spools, or  within a spool) by enough to matter?

If your goal is just to wind wire onto a coil former then I would have thought you effort would be better spent designing the winding mechanism so that the wire stacked itself correctly. Doesn't a conventional winder sort this out for you? I'm surprised that it's necessary to do anything with any great precision when feeding the wire on, or that there are any benefits in knowing the wire thickness precisely.

If you really do need to know the wire thickness as an academic exercise then I'd use a micrometer. If it's necessary to measure this repeatedly at different places along the wire then I'd pass it between a pair of fixed/floating rollers and use a micrometer to measure the position of the floating roller. But this still feels as if you're solving the wrong problem.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 02:44 pm
Hi,

Thank you all for the answers.

My idea is to spool the wire exactly from one "lip" of the coil former to the other without any gaps. To solve the gap problem, lag works quite nicely. However, even if I measure the wire at several place and use that measurement any slight variation of the wire creates problems when it comes to calculating the amount of turns required (coil_length / wire_diameter). Over several thousands of turns even a variation of 0.001mm can amount to a gross gap. I was thinking that actively measuring the wire diameter for discrepancies would allow me to set the number of turns as a "moving target" during coiling so that the wire ends up exactly at the lip.

Perhaps I should be looking for a strategy/some kind of sensor that would be able to sense the presence of the wire when it reaches the coil lip instead of trying to measure the error? I want to minimize contact with the wire as it is coated with a fine layer of plastic (that I want to avoid stripping away).
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jolphil on Jan 21, 2013, 03:14 pm
Hi,
How much variation is in the wire itself or  the thickness of the insulating coating? How would this effect your project?
Goodluck,
jolphil
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: PeterH on Jan 21, 2013, 04:36 pm
Are you trying to determine when a single layer of the coil has reached the far lip (and presumably needs to reverse to form a new layer), or when the layers of the coil have built up to the required outside diameter?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 04:47 pm

Hi,
How much variation is in the wire itself or  the thickness of the insulating coating? How would this effect your project?
Goodluck,
jolphil


There is enough variation that taking several 0.001 precision measurements of the wire and using an average to calculate the amount of turns (coil_length / wire_diameter) yields inconsistent results. This can be due to the coating or other imperfection in the wire. This affects my project because I aim to make "multi-layer" coils and so I need to be able to stop exactly at the "lip" of the coil before reversing the direction of coiling.

If there is still a gap left between the wire and the coil lip, the reversal is problematic.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 21, 2013, 04:51 pm

Are you trying to determine when a single layer of the coil has reached the far lip (and presumably needs to reverse to form a new layer), or when the layers of the coil have built up to the required outside diameter?


Yes;

I am trying to determine when a single layer of the coil has reached the far lip in order to properly reverse to form a new layer.

Stopping exactly on the far lip is required in order to properly reverse to the new layer and keep a tight packing without overlaps. When using a single average value for the wiere diameter, the accumulation of error over thousands of turns yields inconsistent results (i.e. the wire will stop before or after (spool unto itself) the far lip).

Basically, I am trying to find a way that will guarantee that the wire will always stop exactly at the far lip.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: JimboZA on Jan 21, 2013, 05:07 pm
Quote
Stopping exactly on the far lip is required in order to properly reverse to the new layer


But unless the error was such that you had accumulated an integral number of wire thicknesses, that's not going to help.

Let's say it nominally holds 100 turns along the length. You measure that the wire is a bit thicker say, and by the time you get to where the 99th row  would be, you think Oops, we've actually got 99.5 thicknesses. So what do you do? You can't fit another full turn into 0.5 of turn's gap, so you can't stop exactly on the far lip anyway... not in terms of wire widths.... so you reverse with half a wire width gap.

(That made sense to me in my head- might need a drawing to describe it but I cba doing that right now.)

Point is, I'm pretty sure there are best-practices for doing this commercially, and I don't think this is one of them with all due respect.

Title: Re: Measuring a very fine wire with 10 µm precision
Post by: PeterH on Jan 21, 2013, 05:09 pm

Stopping exactly on the far lip is required in order to properly reverse to the new layer and keep a tight packing without overlaps.


By measuring the wire thickness you could estimate the number of turns needed but I don't see how you'd ever get it exact.

I don't know whether it would be practical with wire that fine, but I wonder whether it might be more effective to detect the outer diameter change as the wire hits the lip at the end of the former, rather than try to predict when it will hit? If you used a floating pulley, you'd need to detect a movement equal to the thickness of your wire.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: rvasque on Jan 21, 2013, 05:46 pm
Boots, me thinks you're approaching this problem from the wrong direction.

Also, copper wires are force-drawn/pulled through a die at the factory, so they're pretty much the same diameter.  Being able to detect variations of 0.001mm won't do squat to what you're trying to accomplish. It's immaterial.

I would concentrate my efforts on a mechanism for consistent tight winding, and accurate inductance values.  If the wire ends in the middle of the coil (to achieve the correct inductance value), then so be it. Tape the wire at that spot, then run a few inches of flying lead wires, solder to the transformer terminals (or solder to a thicker flying lead wire). The wire doesnt necessarily have to end at the lip. -- thats how commercial audio transformer makers do it.

EDIT:
The core you use for your transformer will also have variations in their permeability. Even if you got your wire diameter detector correct (which I doubt), the next core you grab may be slightly off, and the next transformer you wind will not end up exactly at the lip (to achieve the correct inductance value)... so now what? You're back to where you started.  You cannot predict where the wire should end because you'd have variations in the size and permeability of your core (if you care about getting the right inductance value).
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: Silverdog63 on Jan 21, 2013, 08:34 pm
I try to go back to the original question, how can I measure the wire with that precision ?
I don't think there is a practical mechanical way to achieve such precision.
So what about a digital microscope ?
http://www.leica-microsystems.com/products/digital-microscopes/
well I don't know your budget (there are cheaper options), but the idea is to "enlarge" the wire, and measure the variation of the image. I mean, measure the difference of light transmittance .....  
Maybe it's just an weird idea but I have no other.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: robtillaart on Jan 21, 2013, 09:47 pm
Lets try to design the sensor you need,

design 1: - conductive wire
-----------------------------------
imagine a V shaped sensor that guides the wire.
depending on the thickness of the wire it will be higher or lower in the V shape
make the sides of the V of a conducting material with known (relative to wire high) resistance
The place of the wire will change the resistance of the V as the level where the wire is short-cuts the current.


design 2: - shadow
-------------------------
place a laser let the wire move in front of it.
@10uM a known amount of light will pass above and below the wire
make that minimal @12 uM - you need mirrors at exact angles
place a TSL235 in the laser bundle - this convert intensity to frequency.
when the diameter varies the intensity will vary

laser >-------------------- | -  -  -  -   -  - [sensor]

now shoot!





Title: Re: Measuring a very fine wire with 10 µm precision
Post by: szangvil on Jan 21, 2013, 09:58 pm
Best option is to use an optical microscope. "Seeing" 1um is not hard at all. Get a decent CCD camera from Pixelink or Basler or any other brand with a 1" sensor and a pixel size of 2-3um. You'll also need a microscope and some basic image processing to automatically identify the wire (easy when looking for a straigth line on a uniform backgound)
It shouldn't cost more than $1000.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: osterchrisi on Jan 21, 2013, 11:01 pm
Hello, I think the weapon of your choice would be a so called 'micrometer'  :P http://en.wikipedia.org/wiki/Micrometer

Plus: If you want to measure in such small dimensions, be aware of the fact that even the warmth of your hand and also the atmosphere around the wire has an impact on the extension of the wire. I'm going with vasquo's oppinion.

//edit: With what I want to say: If you're going to measure a wire by applying voltage, it will expand slightly due to warming up slightly (electrons colliding inside the copper), so I assume you can basically forget that...
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: Silverdog63 on Jan 21, 2013, 11:34 pm

Hello, I think the weapon of your choice would be a so called 'micrometer'  :P http://en.wikipedia.org/wiki/Micrometer


No I don't think so, resolution and precision are not enough
maybe something like this ...
http://www.keyence.com/services/download.php?file=im6000_ka.pdf&fs=IM-6000&ws=none&img=oc_cmm_lp.jpg&layout=d2d&lil_id=1309212783&lil_ly=aln-l_tfsz-20_dfsz-16&aw=gagooglekaim899063b&gclid=CLC97ta9-rQCFUFb3god9Q8AvQ
but again, the budget is ?
I think szangvil and robtillaart have the point.

Title: Re: Measuring a very fine wire with 10 µm precision
Post by: rvasque on Jan 21, 2013, 11:53 pm

Lets try to design the sensor you need,

design 1: - conductive wire
-----------------------------------
imagine a V shaped sensor that guides the wire.
depending on the thickness of the wire it will be higher or lower in the V shape
make the sides of the V of a conducting material with known (relative to wire high) resistance
The place of the wire will change the resistance of the V as the level where the wire is short-cuts the current.


You do know the wire is insulated (and not BARE). It's a "magnet" wire, the kind used to make coils. If you strip the insulation just so you can measure it's resistance, well, you just made your coil useless.

I think the OP needs to visit an audio transformer manufacturer so he can see how it's done. These guys don't measure their wire diameters to micron precision or use lasers or microscopes as they wind. But they do measure their inductance and DC resistance values. They don't care where the loop ends. Overwind a few extra turns, measure, unwind, measure, tap it, then tape it.  Done. 

Have you guys seen the insides of an audio transformer?
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: PeterH on Jan 22, 2013, 12:21 am

The place of the wire will change the resistance of the V as the level where the wire is short-cuts the current.


I don't think that would work, because the wire is insulated. Using a camera and microscope seems like the most likely approach to me, but the other option would be to create a rolling version of a standard wire gauge (using a pair of opposed precision ground rollers with a slight taper, and angled so that they tended to pull the wire away from the narrow end of the V as it rolled between them). The height of the wire in the gauge would tell you the thickness of the wire to whatever precision you wanted, as long as your rollers were sufficiently accurate.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: zoomkat on Jan 22, 2013, 01:29 am
For initial optical testing, there seems to be inexpensive microscope cams up to advertised 800x power.

https://www.google.com/search?q=webcam+microscope&num=100&hl=en&lr=&tbo=d&source=lnms&tbm=shop&sa=X&ei=ndz9UP6aE-iD0QH6oIHoDw&ved=0CAwQ_AUoAA&biw=1173&bih=642
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: Jack Christensen on Jan 22, 2013, 01:42 am
If we're winding inductors here, the inductance of a coil is proportional to the number of turns squared. If the aim is to produce an inductor with a specific inductance, then the number of turns would be the important parameter to control. There should be little effect if things get scrambled a bit at the ends.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: Jack Christensen on Jan 22, 2013, 02:02 am
Thinking further, the concept of measuring one parameter (wire diameter) and calculating the number of turns based on that is flawed. It is an open-loop system and doesn't take a myriad of other variables into account, therefore the calculation will never be perfect. What if the next batch of forms are slightly different in size? What if the standard deviation of same changes? Etc. etc.

A better approach would be to somehow sense when the winding reaches the end of the form rather than calculate it. This is a feedback mechanism that allows for all those other variables (including the ones we haven't thought of) and doesn't require constant measurements of the input (wire). Maybe it's the angle of the wire from the supply point, or maybe tension, etc.

I can buy any number of products that are neatly wound on their spools, e.g. string, thread, wire, solder, etc. There must be some fairly common mechanism to do this that you just need to discover. The wheel has already been invented here. The question I would ask is how are all these other products wound on their spools neatly, not how can I invent an original contraption to do it.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: dan38711 on Jan 23, 2013, 03:24 am
Hello all, I want to thank you for your participation in this thread so far. My name is Dan and am Boots507's colleague. I would like to better explain our motivation for creating "perfectly" wound coils. In Non-Destructive Testing (eddy-current), electromagnetic coils interact with conducting samples via induction processes. Theoretical models can be compared to experimentally acquired data in order to infer geometrical and electrical properties of the sample. However, this approach requires integrating the electric filed over the cross-section of the coil. Thus, these solutions are highly sensitive to the quality of the coil. More explicitly, they assume that the coil has a uniform turn density and a rectangular cross-section. Therefore, we need a machine that creates ideally stacked coils.

An exact solution gives the theoretical inductance of a coil based on inner diameter, outer diameter and number of turns (uniform turn density and rectangular cross-section).  Coils that I have wound very carefully by hand agree almost perfectly, whereas sloppily wound coils deviate significantly.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jolphil on Jan 23, 2013, 02:59 pm
Hi Dan,
While in the past I have wound a few coils with AWG 44 wire,ever  none  needed that type of precision..My gut
feeling is this may be almost impossible . I guess I do not fully understand your problem but just to throw this out.
Why can you not wind your coil as precise as you can in practice, and later in some uniform  test, add or subtract some correction factor so that each coil results in a uniform result.All the previous posts pointed out the pitfalls and problems in trying to get absolute winding results..
Anyway,
Goodluck
jolphil
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: PeterH on Jan 23, 2013, 05:26 pm

Coils that I have wound very carefully by hand agree almost perfectly, whereas sloppily wound coils deviate significantly.


Where on this spectrum from perfect to useless do ordinary machine-wound coils using simple turn counting fall? Would it not be sufficient to machine-wind one layer of the coil, manually pause it at the end of the layer and note the number of turns, and then program the winder to use the same number of turns for the other layers? This could be a very simple process if your CNC controller was designed to support it, and without needing any exotic measuring techniques. It seems unlikely to me that you would need to deal with variations in the wire thickness within a single spool, and I expect that once you have got it set up for one coil you could then continue to wind multiple similar coils with the same settings.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: jean507 on Jan 23, 2013, 08:33 pm

Would it not be sufficient to machine-wind one layer of the coil, manually pause it at the end of the layer and note the number of turns, and then program the winder to use the same number of turns for the other layers?


PeterH,

To me and Dan this seems likes a very good approach to the problem. Although it adds a step in the calibration of the spooling machine to get the number of turns (and consequently the theorical diameter); it seems reasonable to think that from that point on a multitude of coils could be wound using the setting acquired during the calibration run.

I am going to give it a try tonight and report my findings as soon as possible.

Thanks for the idea
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: Jack Christensen on Jan 23, 2013, 09:49 pm
Roughly speaking, what is the production volume required? Tens, hundreds, thousands ... ? Also production rate, how many per day, hour, or whatever.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: GoForSmoke on Jan 23, 2013, 10:43 pm

This (http://en.wikipedia.org/wiki/File:Accuracy_and_precision.svg) is a nice diagram explaining the difference between accuracy and precision


In machining we would specify that precision as 'tolerance'. Every cut is to some measure with some tolerance (like +/-0.1 or maybe +0.1/-0.0).
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: retrolefty on Jan 24, 2013, 02:30 am


This (http://en.wikipedia.org/wiki/File:Accuracy_and_precision.svg) is a nice diagram explaining the difference between accuracy and precision


In machining we would specify that precision as 'tolerance'. Every cut is to some measure with some tolerance (like +/-0.1 or maybe +0.1/-0.0).



But even the device(s) used to measure that such 'tolerance' is within specification or not is subject to a variation in precision. Accuracy is a poorly understood property in the real world.

Lefty
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: GoForSmoke on Jan 24, 2013, 03:52 am
Where I worked we held close tolerances and sold parts that met them. We had plaques from RCA and Kodak for going a year at a time with zero rejects. We weren't trying to hold any better than we could make but we did precision work within tolerances every day.
Part of it is not trying to hold impossible tolerances, but you have to know not only what's possible but what's practical in order to do business. Not just theory, we made the parts.

Why not turn the windings at 1 diameter + (tolerance * 110%) apart per turn? When you come back across the new layer will sit on top. Or is there some reason why the windings have to jam in side to side all along the coil? Does this wire vary thickness by even 10%? You'd get a tighter pack if the diameters set in a hex pattern anyway.

Title: Re: Measuring a very fine wire with 10 µm precision
Post by: robtillaart on Jan 24, 2013, 08:41 pm
Quote
You'd get a tighter pack if the diameters set in a hex pattern anyway.

I hear hands on experience!
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: PeterH on Jan 24, 2013, 11:42 pm

Quote
You'd get a tighter pack if the diameters set in a hex pattern anyway.

I hear hands on experience!


I don't see how they can do, because alternate layers are wound in opposite directions.
Title: Re: Measuring a very fine wire with 10 µm precision
Post by: GoForSmoke on Jan 25, 2013, 12:29 am
They could still be sure how many turns to make per layer without needing to monitor wire thickness. Even the wire should have dimensions and tolerance.

Title: Re: Measuring a very fine wire with 10 µm precision
Post by: retrolefty on Jan 25, 2013, 03:15 am
All the automatic or semi-automatic coil winders I've ever seen just relied on a turns counter for feedback and assuming normal tolerances of the bobbin size and wire gage, I would think it would turn out very repeatable induction values, and many of them turned out beautiful looking windings. One could always measure the final induction value and trim if needed. As far as creating a 'perfect' symmetrical magnetic field, I have no idea how critical or difficult that can be nor if wire gauge variation would have an effect, turns is turns.

Lefty