Voltage sensing feeder

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So - I recently sold my little hobart handler 135 mig machine, and bought a Miller XMT300cc/cv and 22a feeder from the other tech at our shop.  He wasn't using it and I wanted more power....     I do like the speed of the metal hot glue gun for some fabrication, and while I did really love the little Hobart it struggled on anything very thick.  Plus - I may someday try a aluminum spool gun - though I sure like tigg'n alum.I've been mostly Tig welding lately, but I've got this new toy so I want to practice with the new setup and get it figured out.  Lots more settings to screw up you know.I do have the Miller power course so I can read up on voltage and wire feed speeds (or just use the handy-dandy calculator that came with).My question though is:This feeder has the voltage sensing lead.  I've downloaded the owners manuals for both the XMT and the 22a, but I can't figure out what the voltage sense feature does.  Duh - it senses voltage dummy...Ok - but how does that affect the weld output?  Neither manual mentions it - the 22a manual shows which internal switch settings I need to use for "power supplies that support pins F and H" and "power supplies that don't support pins F and H."  Apparently from looking through the XMT manual it doesn't support pins F and H.  So I'd better check my switch settings.  But - that still doesn't tell me what it (the voltage sensing feature) does.Anyone have one of these setups and can tell me what it does?  Is it merely a readout of actual voltage during welding, or does it affect the weld power output?Thanks - MichaelOh - and it did come with the HF-251 box, so I can Tig with it too.  Lucky me!  But no AC.   Too bad 'cause that XMT puts out boatloads of power even on single phase (for me anyway), without sucking much power out of the wall.
Reply:As I understand it, the voltage sense wire is used with a CC power supply, so the wire feeder can regulate wire feed speed based on voltage.
Reply:Oh boy volt sensing feeders. Ready for your brain to swim? Here we go.The 22A IS NOT a true voltage sensing feeder, it is still a constant speed feeder with a clip to give a voltage feed back. Its power is still supplied by a control cable. The 22A will NOT change speeds during welding and will not regulate wirespeed based on voltage, and is for use on CV machines only. The volt sense clip on your 22A is for the sole purpose of displaying voltage at the feeder. For the 22A you will not have amperage and voltage feedback pins populated in the connector (pins F & H) unless you have the optional meter kit.,if you unhook the clip, you will lose your voltage display. There are several models of XMT 300's, I am assuming your is the XMT 300 CC/CV, which does support pins F and H.True volt sense feeders are powered by arc voltage rather than through a 24V signal sent from the power source (older equipment used 115V) like remote control feeders such as your 22A. A remote feeder has a control cable that contains wiring that supply the 24volt power to operate the feeder, contactor closure control, and amperage and voltage feed back.  A true volt sense feeder will have no control cable, instead relying on power supplied by the arc. A volt sense feeder will also use its own contactor rather than the contactor at the power source. When operating with a CV (constant voltage) power source such as your XMT 300, the voltsense feeder with behave very much like a bench top feeder. The volt sensing clamp with still need to be hooked to your work in order to power the feeder. Because there is no control cable to attach, industries that need to weld a long distance from the power source such as construction, field repair, and even pipeline prefer this type of feeder. With a CV feeder you will preset your voltage which will remain constant, and adjust your amperage through wire speed. Where the volt sensing really comes into play is when the machine is run on a CC (constant current) power source such as a stick welder things change. Instead of holding voltage constant you now are holding current constant. Now that your voltage is fluctuating this means that your arc length will vary. Well, this is not very good when feeding wire. So what happens is as your arc length increases the feeder will "sense" a change in voltage. It will compensate for this change by manipulating the speed of the wire to keep the voltage at an acceptable level. For instance, if your arc length gets too long the feeder will sense an increase in voltage and will increase the speed of the wire to shorten the arc length. It will slow wire down if the arc length gets to short and voltage starts to go down.  When feeding wire on a CC power source we now preset our current to remain fixed and adjust our voltage through wire speed. A very important note is if you have CV capability use it for wire welding.  CC welding of wire is very difficult and is NOT recommended.Last edited by reddoggoose; 08-08-2007 at 10:10 AM.
Reply:I have the 22a and mine doesn't have voltage sensing.  You sure yours does?  I don't know much about the different variations of them though.
Reply:Welder boy,Your 22A problably doesn't have the meter option. The lead is needed to read voltages displayed on the feeders meter option.
Reply:Ok - that sort of makes sense I think.This 22a does have the meter option with voltage sensing lead.  Pins F and H are populated in the 14 pin connector.  It does not have the optional feed in etc potentiometer controls (not that it would matter to this discussion).The XMT is a CC/CV version of the power supply.The 22a seems to work fine with or without the clip attached, and in fact the clip doesn't seem to matter at all to operation or display.I took a look at the dip switch settings on the meter board - they are all in the up position.  According to the manual for the 22a, positions 1 and 2 are for the voltage sensing function, and should be 1 up and 2 down for supplies that support F and H, or 1 down 2 up for supplies that don't.  It doesn't show any settings for both up, so I guess I should fix that.Now you say the XMT does support pins F and H, but I don't see it in the manual - On page 7 of the pdf it shows pin assignments for both the remote 14 and the remote 17 receptacle - the 14 assignments don't show inputs for voltage sense or amperage sense on any of the pins, and don't show anything assigned to F or H.  The remote 17 receptacle does show sensing on pins E and M.  Is the manual wrong?Based on that - it looks like I should set the switch to 1 down 2 up.And if I read you correctly - at that point it should be a display only option with no change in operating parameters - is that right?Michael
Reply:Originally Posted by reddoggooseYour 22A problably doesn't have the meter option.
Reply:Originally Posted by bateman147Ok - that sort of makes sense I think.This 22a does have the meter option with voltage sensing lead.  Pins F and H are populated in the 14 pin connector.  It does not have the optional feed in etc potentiometer controls (not that it would matter to this discussion).The XMT is a CC/CV version of the power supply.The 22a seems to work fine with or without the clip attached, and in fact the clip doesn't seem to matter at all to operation or display.I took a look at the dip switch settings on the meter board - they are all in the up position.  According to the manual for the 22a, positions 1 and 2 are for the voltage sensing function, and should be 1 up and 2 down for supplies that support F and H, or 1 down 2 up for supplies that don't.  It doesn't show any settings for both up, so I guess I should fix that.Now you say the XMT does support pins F and H, but I don't see it in the manual - On page 7 of the pdf it shows pin assignments for both the remote 14 and the remote 17 receptacle - the 14 assignments don't show inputs for voltage sense or amperage sense on any of the pins, and don't show anything assigned to F or H.  The remote 17 receptacle does show sensing on pins E and M.  Is the manual wrong?Based on that - it looks like I should set the switch to 1 down 2 up.And if I read you correctly - at that point it should be a display only option with no change in operating parameters - is that right?Michael