Measuring wire gauge? - Page 1
Forum section: electronics / beginners

author: LektroiD
author_rank: Frequent Contributor
timestamp: July 07, 2016, 12:08:01 pm
content: Ok, I can use a vernier calliper on my existing wire to determine the overall thickness, but when it comes to buying wire, I haven't got a clue what I'm looking for... Should it be 16SWG, 14AWG, or 55/0.1mm, and how do all of these relate to each other?I know you can buy those measuring discs, but they seem to only measure SWG standard, how can I find the AWG equivalent that some websites use? And what does 55/0.1mm mean in physical terms? I presume it is something to do with the amount of strands and thickness of each strand... Does AWG or SWG have a set standard of the thickness or amount of collective strands, or only a measurement the outer coating?Youtube has absolutely nothing of value, and the Google 'can of worms' responses make it more complex than it really needs to be, particularly with the added hindrance of imperial and metric thrown into the equation...If anyone here could illustrate this in easy to understand terms, that would be brilliant.

author: McBryce
author_rank: Super Contributor
timestamp: July 07, 2016, 12:20:44 pm
content: http://www.coilwindingmachines.eu/engineers_corner/awg_swg_converter.html(This one even does inches)The dimensions are always the total diameter of the conductor, this doesn't include the outer insulation. When it comes to wiring, the conductor dimension/material will define how much current it can take, the insulation dimension/material will define how much voltage.McBryce.

author: retrolefty
author_rank: Super Contributor
timestamp: July 07, 2016, 12:33:40 pm
content: Quote from: McBryce on July 07, 2016, 12:20:44 pmThe insulation material also defines the max temp rating of the wire.

author: McBryce
author_rank: Super Contributor
timestamp: July 07, 2016, 12:34:53 pm
content: True, forgot that bitI was just thinking in electrical properties.McBryce.

author: Ian.M
author_rank: Super Contributor
timestamp: July 07, 2016, 12:57:50 pm
content: For electrical purposes it all comes down to the CSA (cross sectional area).Lets get stranded wire out of the way first. 55/0.1 mm is 55 strands of 0.1 mm diameter. The CSA of one strand is 0.12*Pi/4 mm2. Multiply that by 55 strands and you get a total CSA of 0.432 mm2.The CSA and the bulk resistivity of the metal (usually 99.9% pure electrical grade copper) determine the resistance per meter, and the insulation thickness and material determine its surface area, and thus thermal resistance to ambient, which given the ambient temperature and the maximum permitted insulation temperature, (which will be at the conductor surface) determines the maximum permissible dissipation per unit length, which determines the current carrying capacity. Its a total PITA to calculate from first principles so use wire manufacturers tables (but only for their own wire). Building wiring is a different matter, as there are additional derating factors required to comply with regional electrical regulations.Vernier calipers suck for measuring small wire diameters - they generally don't have enough resolution. If you don't have digital calipers or a micrometer, one workaround is to wind ten turns touching each other around a cylinder and measure the width of all together, making sure they are lying flat and in contact, then divide by ten. However as the wire is slightly on the slant, this starts to become inaccurate if the wire diameter is greater than about 1/30 the cylinder diameter and rapidly becomes unusable beyond 1/10 the diameter. For wires <0.5mm dia, an AA battery is a convenient sized cylinder.You'll find various wire gauge charts online for AWG and SWG that give you the diameter and often the CSA for solid wire e.g.http://www.engineeringtoolbox.com/awg-wire-gauge-d_731.htmlhttp://www.engineeringtoolbox.com/swg-standard-wire-gauge-d_1779.htmlMake sure they are from a reputable source! Take ones with current ratings with a large pinch of salt as those depend on the insulation characteristics, so cant be trusted unless you get them from the actual manufacturer of the specific wire, and don't forget to apply the various derating factors.

author: McBryce
author_rank: Super Contributor
timestamp: July 07, 2016, 01:04:39 pm
content: A really comprehensive and accurate explanation Ian, however you may have missed to OP's last sentence: "If anyone here could illustrate thisin easy to understand terms"It may be a bit too much for the OP?McBryce.

author: oldway
author_rank: Super Contributor
timestamp: July 07, 2016, 01:06:31 pm
content: Does it help ?

author: Ian.M
author_rank: Super Contributor
timestamp: July 07, 2016, 01:20:56 pm
content: O.K. TLDR: Figure out the CSA you need, either for current carrying capacity, resistance per unit length or simply mechanical strength! Look it up in wire manufacturers catalogs and see what your options are. More strands for the same CSA increases flexibility.. Order from a reputable distributor.N.B. Derate EBAY wire by at least 50% unless you have physically confirmed the insulation is the correct material and grade and the resistance per unit length is within 1% of that predicted from the nominal; CSA. Double-derate Chinese EBAY wire and only use it for non-critical applications!Why? The scum-sucking bottom feeders in the wire manufacturing business use the cheapest recycled copper that's ductile enough to get through a wire drawing die. It certainly wont be as low resistance as electrical grade copper. Its also likely to be undersize and you can bet the insulation plastic or lacquer has been degraded with cheap fillers and extenders and excess plasticiser that compromise its toughness and temperature ratings - if its even the type of plastic it claims to be. I'm not even going to get into the horrors of copper coated aluminium or steel so-called electrical wire.

author: LektroiD
author_rank: Frequent Contributor
timestamp: July 07, 2016, 09:45:10 pm
content: Quote from: McBryce on July 07, 2016, 12:20:44 pmSo, from what I'm understanding here, when using a wire gauge (like the one pictured below), you only put the metal part of the wire in, not the plastic coating?If this is the case, I can imagine it would be hard to measure the SWG of stranded wire... Or is SWG only for measuring single core?

author: Ian.M
author_rank: Super Contributor
timestamp: July 07, 2016, 10:28:08 pm
content: When it comes to stranded wire, you can either measure a single strand and count them to get the CSA or refer to a manufacturer's stranded wire chart.e.g.http://www.calmont.com/pdf/calmont-eng-wire-gauge.pdfHowever as a rough approximation, the packing fraction of high strand count wire, assuming close packed circular strands is Pi/(2*sqrt(3)), which is near enough 90%. so measure the overall diameter of the conductor, then useCSA=0.9*Pi*d2/4. You need to allow a little for the crevices between the surface strands at lower strand counts, so subtract half the strand diameter from the overall diameter to compensate.

author: LektroiD
author_rank: Frequent Contributor
timestamp: July 08, 2016, 12:11:49 am
content: What is "CSA"? Acronyms are not my strong point and I've seen a few used in this thread (I will reiterate "in easy to understand terms")...Does anyone know of a book written about wire, or a video documentary about this? The more I am reading from here and various sources around the internet, the more convoluted it appears, and the more confused I am with it all...

author: Ian.M
author_rank: Super Contributor
timestamp: July 08, 2016, 12:53:41 am
content: I gave the definition of CSA when I first used it.Quote from: Ian.M on July 07, 2016, 12:57:50 pm

author: IanB
author_rank: Super Contributor
timestamp: July 08, 2016, 01:01:52 am
content: Quote from: LektroiD on July 08, 2016, 12:11:49 amCan you try to explain what your question is in simple terms, because I've read your first post a few times and I really can't understand what it is you want to know?Perhaps if you give an example, like "I need to buy wire for (some particular job I'm doing), how can I choose the right wire for this job?"Without knowing what job you are doing, it is impossible to answer your question. For example, is it building wiring in your house? Chassis wiring in your car? Low voltage wiring in an electronic project? High current wiring in a remote control aircraft? Or...?

author: LektroiD
author_rank: Frequent Contributor
timestamp: July 08, 2016, 01:30:41 am
content: Quote from: IanB on July 08, 2016, 01:01:52 amVarious applications, mostly electronic music circuits (supply voltage, control voltage, gate signals, etc). Basically, I would like an understanding of wire in general, so when I order some for a particular project, I'm not stuck not knowing the thickness of each SWG...I recently bought some stackable banana plugs, and wanted to use the same thickness of cable as my existing banana cables, but didn't know how to measure it.I'm quite surprised something that is evidently appearing to be a rather complicated subject has no books written about it, and not even a single youtube tutorial video...

author: IanB
author_rank: Super Contributor
timestamp: July 08, 2016, 03:09:52 am
content: Quote from: LektroiD on July 08, 2016, 01:30:41 amOK, in simple terms:Wire has three main characteristics that you might need to care about:1. Thickness (or cross-sectional area). This matters in three ways:- in low voltage wiring, how much current it can carry without too much voltage drop- in mains voltage wiring, how much current it can carry without overheating (or being compliant with wiring codes)- in either case, look up wire sizing tables online to find out- in any wiring, how light and flexible it is (thicker wire than necessary can be a pain to use and install)2. Insulation- what voltage is the wire rated for?- for low voltage project wiring this basically doesn't matter- for test leads it might matter if high voltages could be encountered3. Flexibility- how easily does the wire bend?- can it bend without breaking?- flexible wire is multi-stranded, with more thinner strands making it more flexible- single core wire is not flexible and should only be used for fixed installations- specially flexible wire (for example, for test leads) may also have softer insulation than other wireFor your described applications you are looking for "hookup wire" or "test lead wire".Typical thicknesses for hookup wire are 22 to 28 AWG (with 24 or 26 being average). Look up conversion tables for metric or SWG equivalents.Test lead wire generally comes in a standard thickness, you just choose what colour you want it and how flexible you want it.For general low voltage electronic use you probably will find multi-stranded 24 AWG wire in various colours to be a good starting point.