# MIG - measure Volts, Amps, wire-feed-speed

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Hello all

Getting into MIG welding. However, my notebook full of arbitrary settings for different machines like "2-4,8","1-3,2~1/3", "6A,7" and so on (in my own notation, this is "(,)")

Problem is, if machines are different, is "2-2,7" the same condition as "6A,7", for instance?

How do you measure Volts and Amps on a MIG welder? And can you measure wire feed speed in say metres-per-second or inches-per-minute?

Richard Smith

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Any regular electronic voltmeter can be set on volts scale and connected between the power lead and ground lead. You could do it at the power supply or at the feeder and the ground. Amperage is pretty hard to measure unless you have a very heavy ammeter that can take the load. To measure feed run the wire out for six seconds, measure and multiply by ten for your rate per minute. Sometimes dials are marked with the feed per minute and on later models it is given via a digital readout on the feeder. One on Miller's articles gives conversion from feed rate to amperage for different wire diameters. I will look around again for it. Randy

Getting into MIG welding. However, my notebook full of arbitrary settings for different machines like "2-4,8","1-3,2~1/3", "6A,7" and so on (in my own notation, this is "(,)")

Problem is, if machines are different, is "2-2,7" the same condition as "6A,7", for instance?

How do you measure Volts and Amps on a MIG welder? And can you measure wire feed speed in say metres-per-second or inches-per-minute?

Richard Smith

• posted

Try page four for some amperage guidelines. Randy

Getting into MIG welding. However, my notebook full of arbitrary settings for different machines like "2-4,8","1-3,2~1/3", "6A,7" and so on (in my own notation, this is "(,)")

Problem is, if machines are different, is "2-2,7" the same condition as "6A,7", for instance?

How do you measure Volts and Amps on a MIG welder? And can you measure wire feed speed in say metres-per-second or inches-per-minute?

Richard Smith

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Something like this

be pretty groovey for that.

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Thanks Randy

Simple but 100% effective. Will work for every machine I now encounter.

Overlooked this - that no machine I now meet and most participants on the group meet has a "soft-start" - so can do this. Bend the wire over at the tip by 90deg, pull the trigger for 6seconds and measure from the contactor to the bend.

Randy - reason I overlooked this - when doing my welding research in the 90's most of the machines I met were "top of the range" - very expensive machines - with "soft start". So that technique wouldn't work.

Explanation - with "soft start" the wire feeds slowly until an current is drawn (the arc starts) whereupon the wire-feed gets going at its set value. Makes starting your weld easier. So when you pull the trigger with the torch pointing up in the air, the wire feed you see is much slower than the feed rate when welding.

Guess "reactive filter" helmets, where you can see what you are doing as you line up the torch, make the soft-start less important these days(?).

I'll go looking up the wire-feed-speed to amps chart - many thanks.

Richard S.

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Randy, everyone

This - the Miller manual you mention - was really interesting for me. It suggests what might be called a "current-lead" method to find your settings on the MIG welding machine -- works because:

• for MIG welding you want the 1Amp-per-0.001inch of thickness used for eg. TIG welding

• you can estimate current from wire-feed-speed given the wire diameter.

• you can measure wire-feed-speed easily

I've been shown a voltage-lead method which is much more trial-and-error.

Appended is Miller's current-lead method, as best I can transcribe it into text without their diagrams:

Richard Smith

--------------------------------

from

illustrated explanation on pg4

Setting up a MIG machine - current-lead method

Taking example of 1/8th-inch=0.125in (3mm) plate

Currentthickness rule -- 1Amp per 0.001inch of thickness (40A per mm)

So looking for 125A

Consider/survey/select wire size (diameter) options given their current range. Wire-size | Amp-range

0.8mm (0.030in) | 40-145A 0.9mm (0.035in) | 50-180A 1.2mm (0.045in) | 75-250A

Each of these three wires accommodates the 125A needed

Deduce from known wire feed speed current relationship the wire feed speed needed, then set it with MIG machine's wire feed speed adjuster

The w.f.s. current relationships

Wire-size | Recommendation

0.8mm (0.030in) | 2 inches-per-minute per Amp 0.9mm (0.035in) | 1.6 -"- 1.2mm (0.045in) | 1 -"-

So for our 3mm (1/8th-inch) weld, would be Wire-size | calculation | w.f.s. 0.8mm (0.030in) | 2 * 125 | 250ipm 0.9mm (0.035in) | 1.6 * 125 | 200ipm 1.2mm (0.045in) | 1 * 125 | 125ipm

Select voltage

Low voltage -> wire "stubbing" Correct voltage -> smooth running (the "rasping" sound) High voltage -> arc unstable, spatter

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A standard voltmeter can read the volts while welding. To measure the amps you need a DC amprobe clamp. I have one that plugs into my Fluke meter.

Most amprobe clamps are for AC only.

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I'd like to add the best spot is likely on the Gnd return - as other conductors are not present running switch currents and noise.

The Ac/Dc Amprobes use a hall effect device that measures the current to an amplifier and then to the electronics. AC is more turns ratio and rectified for the electronics.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder

Ernie Leimkuhler wrote:

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Something that many people don't realise is that amperage on wire feed constant voltage machines can vary widely. Increasing or decreasing stickout can change amperage down or up 25 amps from the ideal stickout. When one gets up into the higher amperages this can make a significant difference in the weld bead. The amperage is only an approximation. Each operator will be using the same settings and yet be running a different amperage depending on stickout used. Most weld procedures written up for critical welding will include the stickout to be used by the operator. Randy

This - the Miller manual you mention - was really interesting for me. It suggests what might be called a "current-lead" method to find your settings on the MIG welding machine -- works because:

• for MIG welding you want the 1Amp-per-0.001inch of thickness used for eg. TIG welding

• you can estimate current from wire-feed-speed given the wire diameter.

• you can measure wire-feed-speed easily

I've been shown a voltage-lead method which is much more trial-and-error.

Appended is Miller's current-lead method, as best I can transcribe it into text without their diagrams:

Richard Smith

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That looks like it works on both sides of the pond - 50 and 60 Hz and then some. So it must be Hall effect - and a quality IC inside.

Have no idea on price - but it is qualified by many countries around the world by the special seals.

I have a low cost one like this - and a 1000 amp HP version that plugs in.

I like the peak hold - as I'm not normally fast enough or even around when peak comes. RMS is good for the longer versions of the voltage - not surges at current starts and such.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder

JensenC wrote: