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7th Aug 2021, 12:44 PM #16
Does it, and should it?
I don't know, in reference to this particular example. Hence why it would be nice to see what it puts out, and how clean the signal is.
I have many welders, but not an AIG... so...'for science!'
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7th Aug 2021, 01:56 PM #17Senior Member
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7th Aug 2021, 05:25 PM #18Intermediate Member
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OK the CRO traces.
More interest in these than I expected, will post up soon.
I saw a couple of questions in the recent posts.
Michael.
Yep the welders minimum actual output is 22A as measured, even when the meter says I'm set for 10A. The meter is not 'live' it does not follow the pedal position but just seems to be a digital indicator of the knob position.
On the graph I posted, the red line is what the machines meter says (set by the Peak Current knob), the blue line is what's actually produced at the torch as measured on the probes. There is a positive current offset actually, around 10-12A, reducing as it gets towards 200A.
I have had a play with all the possibilities of the pedals own knob combined with the pedal travel, and anything else I could think of.
22A at is the real minimum of my example of this machine it seems, so perhaps why I find it harder than should to weld very thin ally(on edge)
Jack.
The other probe is a Tektronix A622
https://au.element14.com/tektronix/a...khz/dp/7986874
https://www.farnell.com/datasheets/2239667.pdf
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7th Aug 2021, 05:29 PM #19Intermediate Member
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This a reasonable diagram for reference...
Slight side note.
This diagram (shamelessly pirated from Millers pages) I think relates well to this style machine, ignoring the three phase mains supply of it though, the AIG TIG 200P is of course single phase 240V.
TIG block diagram 1.gif
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7th Aug 2021, 05:34 PM #20Intermediate Member
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Test setup.
Here's how I setup the torch for testing. I didn't move the torch between samples (except to change to the ally setup for AC).
TIG 200P and fluke probe.jpg P7290023.JPG P8020052.JPG
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7th Aug 2021, 05:39 PM #21Intermediate Member
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OK the CRO traces.
These are captured using the Tektronix A622 connected to a 100Mhz digital CRO (and recording the screens with a regular camera).
A baseline trace in DC coupled input mode on the oscilloscope below. The right side of each image shows the trace measurement values as determined by the oscilloscope firmware. This is usually pretty accurate on steady signals, but didn't like pulse modes (as expected).
DC at 50A(selected via knob), no pulse. Shows fairly constant DC at about 64 Amps (which agrees with my graphing at 50A selected), with about 7 Amps of high frequency ripple on it. OK I think, the welder runs DC TIG mode on steel beautifully, sounds and looks very smooth...
50A DC TIG.jpg
This trace below is when I changed oscilloscope time-base & offset and captured the ripple in detail. The frequency of the ripple is 94kHz, and I think is remaining from the primary (first) inverter after the second filter (if the machine is like the diagram I posted earlier at all).
50A DC primary inverter ripple.jpg
The is DC pulse turned ON (slow setting) at 10% duty cycle on the left, and same at 50% duty cycle on the right.
DC Pulse @ 10% Duty.jpg DC Pulse @50% duty.jpg
AC Mode.
This is running 50A AC (as selected by knob) no pulse, AC balance set to 0 position (mid range). This trace reveals the machine generates AC TIG at 62Hz (from secondary inverter), nice to know that...
50A AC with AC balance at 0 pos.jpg
This is 50A AC no pulse. Left image has AC balance set to minimum (-5 position). Right image has AC balance set to +5 position.
50A AC with AC balance -5 pos.jpg 50A AC with AC Balance +5 pos.jpg
This is AC TIG with pulse on (slow setting). Right side shows a couple of pulse cycles. Middle is zoomed in on time-base. Right is zoomed further to look at how well it switches between high and low pulse.
80A AC slow Pulse .jpg 80A AC Slow Pulse ~5Hz.jpg 80A AC slow pulse again.jpg
AC fast pulse setting, fastest position selected. These two traces show not much happening on the 62Hz AC when pulsed this fast, I suspect a limitation of a fixed 62Hz frequency AC while attempting to pulse it at a much higher frequency
AC fastest fast pulse at 10% duty.jpg AC fastest pulse setting 90% duty.jpg
I think the output of the machine is reasonably clean, but I will try measure the same traces on a local friends Metalmaster 215 Elite and see what a much more expensive fully digital machine looks like soon...
My takeout form all this is that the machine runs 62Hz in AC TIG (not adjustable), the frontend inverter runs at 64kHz, the AC output of the secondary inverter is Squarewave. All the basics do what they are supposed too, slow pulse works nicely. And now if anything changes I have a baseline set of traces to diagnose issues with
If anyone wants me to grab another trace of something I didn't think of, specify what it is under what conditions and I'll do it for you.
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8th Aug 2021, 11:29 PM #22Intermediate Member
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9th Aug 2021, 12:17 PM #23Senior Member
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Thanks for posting those - it's nice to see what's expected.
Only square wave so no need for a burst of HF at the zero crossings and I still think that would only be needed if an actual sine wave were generated.
I am having trouble picturing you welding with one hand and snapping pictures of the CRO screen with the other. That's the only picture that's missing I think!
Jack
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9th Aug 2021, 06:45 PM #24Intermediate Member
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The picture is sort of there. The two torch images in the post prior show the torch set into the orange magnetic holder I normally use between welds, but in this case I raised the metal up to the tungsten instead and left it in that position.
So both hand free for the scope and a foot for the pedal. I made sure the results from maxing out the pedal or using the torch switch got the same values (which they were).
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21st Aug 2021, 01:54 PM #25Intermediate Member
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New toys for the AIG TIG 200P
A couple of cheap new things turned up this week for me to use with the TIG...
In keeping with the whole 'budget priced' theme of this TIG welder, I had spent very little money on AliExpress to see what I could get.
A $55 WP-17 size TIG torch (including post), and $20 on a universal sewing machine control pedal.
So I've run a few test welds with the WP-17, and I can right away see why welders like them. They are so much lighter and the cable is so much more flexible that the supplied WP-26, I quickly forgot it had a cable on it.
Build quality of the kit is OK. The WP-17 head is made quite well, I had the torch handle off to remove the trigger switch (I have a pedal) and the brass cable/hose fittings look good and braised together very well.
It uses 10mm Sq cable (or so it says on the cable...).
I did notice it gets hotter around the head than the bigger WP-26, expected that.
https://www.aliexpress.com/item/4001286747642.html?
The sewing machine pedal is for an experiment to see if it can be adapted to run the TIG. It has a 20Kohm pot internally, but no HF start switch, so I'll have to fit one.
The reason I'm doing this is because the AIG pedal I bought is so big and industrial. It's meant for steel capped boots in a factory I reckon, not my New Balance size 11 sneakers...
Anyway, if it works out somebody might be interested...
P8210081.jpg P8210084.jpg P8210085.jpg
Also, I spent some time at a friends place last weekend taking current measurements and oscilloscope traces like I did with my AIG. He has a very nice Metalmaster 215 Elite AC/DC TIG machine. I was curious how accurate it was compared to my budget machine (the 215 Elite is priced at around $2500 currently I think). If anyone is interested I can put a thread with the data.
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21st Aug 2021, 02:27 PM #26Senior Member
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If you already have the images then yes, I'd love to see them.
Aside from general curiosity, it will be interesting to see how the delivered current compares with the current selected. Curious to see how HF is implemented as well.
Thanks
Jack
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22nd Aug 2021, 11:18 PM #27Diamond Member
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