Volt Meter?

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I have a 4 tap 120 volt Firepower machine. Is there a way I could put a volt meter on it? How would I wire the meter at the taps?
Reply:I have no idea...I'm sure someone will come along with the correct answer..But for now..I have no idea.. ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Lets see, electrode positive right?  So heres what you do if you have a volt meter, use a terminal clip and put the red lead on the Positive lug that connects to the ground clamp.  clip black one to the negative lug.  The meter will not get hurt.  should work nicely.  The only problem with this is, your not gonna get a reading until the trigger on the gun is pulled.  delimma.You could take something like this: http://www.radioshack.com/product/in...entPage=searchand see what it would take to pull the display loose and run it to the front of the machine, leave the rest of it inside the machine somewhere.  Maybe a little dc power supply (wall wart) could be wired to the ac input and used instead of batteries to run it.  If you can figure out what kind of switch is used to energize the output when the trigger is pulled, well, it gets even more interesting.  Probably a large type relay.  It will allways have the voltage that will be going through it on one side.  It will be an open circuit voltage though, and not the actual welding voltage.  Sound like a fun project that wouldnt hurt anything, cept maybe you.  Filter caps in welders are might powerful, and hold a charge a while.  Most good circuit designs have a discharge loop for power downs to keep em discharged, but who knows without a schamatic?  Stay tuned, Im sure some of the other fella's here have even better ideas.Last edited by Doolittle; 03-17-2007 at 11:20 PM.Various GrindersVictor Journeyman torch200cf Acet. 250cf oxygenLincoln 175 plus/alpha2 gunLincoln v205t tigLincoln 350mpEsab 650 plasmaWhen you can get up in the morning, Its a good day.Live each day like its your last.
Reply:Now what did I tell ya?Someone would be around soon......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I may pursue this a bit. What do you imagine the voltage range or scale would need to be for a 120 size machine?
Reply:It is going to be in the 20V range. I am curious, do you just want to know how the 4 taps are spaced in voltage?This info may be on the machine somewhere or in the manual."Common sense is not very common"http://www.tahoekeyshome.com
Reply:Is this the Firepower FP120 MIG machine?If so, it is rated at 30 volts open circuit, so your voltmeter should be set up for at least 30 volts full scale.  Are you thinking of a DPM (Digital Panel Meter), or an off-the-shelf analog (d'Arsonval, moving coil) panel meter?  If the latter, I think 50 volts would be the closest standard range.For either type you should provide noise filtering to prevent voltage spikes due to inductive kick from the transformer and cables from reaching the meter.  I'd look at schematics of commercial units to see if they provided filtering in front of meters and what configuration and component values they used.  Possible that I'm being too cautious.By the way, what are you going to use the voltage information for?  How are you going to read it while welding?  The open-circuit voltage before you strike an arc doesn't mean much.awright
Reply:Looking at seeing what the voltage is at different taps when welding to compare welding quality. As a newbe, it's just a project to waste some time really. But I am looking at getting digital volt meter, cutting out a section of the welder and running wires down to the + and - outputs. You can get them for $15 or so on ebay. Might sacrafice an old v/ohm meter I have. But I think the voltage meters look better. The pain with digital meters is I'll have to tap the 220 and find a power supply to run the voltage down to 5v or so. The welder is a Firepower 130.  Although I dont think the voltage should change with wire speed, but will it? Would be kinda of nice to have an inductive amp meter as well, but that is a bit more work and money.  I could in needed install a capacitor on the meter side, with may reduce any spiking. You gotton do something with your time..... HA!
Reply:OK. Sound like good enough reasons to me.  Personally, I (and others) have never had difficulty finding something to do with my time.Your observations about requiring a power supply for your DVM suggests that analog panel meters might be a preferable option.  No power requirements, just scaling resistors (and maybe a filter).  I guess we are not far away enough from the panel meter days to give them any cachet for being retro.  They do work, however, and do you really need the voltage or current to three decimal places?A capacitor alone may not be very effective in clipping spikes (if present) or smothing out meter activity since the source resistance of the arc is very low.  For either a DVM or an analog panel meter you will have scaling resistors between the arc and the DVM.  You might be better off putting your filter cap in the middle of the resistive divider to get more smoothing for a given capacitance.You can also provide a current meter by inserting a shunt in series with the welding current path and taking the voltage drop across the shunt to a DC current meter.  You buy a shunt calibrated for (usually, but not always) 50 millivolt drop across the shunt at the specified current and a meter calibrated for full scale reading of 50 millivolts, but with a scale calibrated in amps that matches the shunt.  The resistance of the shunt is low enough that it has negligible effect on the welding circuit.Since you seem to want to expend time, you might think about providing a chart recorder instead of or in addition to meters.  I've considered using a servo chart recorder to document welding current, since it is (obviously) difficult to read a meter and maintain the desired arc at the same time, and I can just imagine how long I would be able to keep my wife trying to read dancing numbers while I hollered out, "NOW - - - no, no, no, - - -  NOW."  If you haunt the surplus joints or attend instrumentation auctions you will see fine laboratory chart recorders selling very cheaply these days because everyone is going digital.  Virtual giveaways are sometimes seen.  With the chart recorder, you will have a complete time history of the voltage, current, or both over the duration of your weld.  I guess that's why my wife calls me, "measurement man."Rather than sacrificing your old VOM, why not just run your signal taps to banana jacks on the front panel and plug in the VOM when you want to take data?  Same with the chart recorder idea.Have fun.awrightLast edited by awright; 03-21-2007 at 10:01 PM.