Measuring a very fine wire with 10 µm precision

PeterH:

Boots507:
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.

dhenry:
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.

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

What are you doing?

vasquo:
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.

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?

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).

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.

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

But how accurate do you want it?

JimboZA:

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.

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.

This is a nice diagram explaining the difference between accuracy and precision

JimboZA:
This 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?

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.

Boots507:
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.

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).

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

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?

jolphil:
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.

PeterH:
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.

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.