Measuring Current?

[Splatfest]

A couple of years ago I acquired a Sip stick welder,its old but it does the odd job well enough.My question is how do I measure how many amps its putting out.It doesnt have any settings as such just a red line in a narrow window on top that moves when you turn the current control on the front can I just stick a clamp type multimeter round one of the leads while its welding
Thanks

 

[matt1978]

Yes you could do that

Whats the biggest rod you can put down??

If its 2.5mm its prob 120amp 3.2mm Dia its prob a 140amp, if its 4mm its prob 150.

Is there nothing on the Data plate that says the max output? If you know the max and min welding values, you can guesstimate the rest by where abouts you turn the pot?

 

[Splatfest]

Thanks for the reply.
I've never tried anything bigger than 2.5mm.There wasnt a data plate on it,there wasnt even any paint left on it Its not very big, I was guessing 100-120 amp.Would be nice to know for sure then I could put some markings alongside the window at say 5 or 10 amp intervals.

 

[GeorgeB]

I guess the minimum current of your arc welder may be somewhere around 45 or 50 amps. When you turn the knob, the core of the transformer is gradually withdrawn. Maximum current (perhaps 100 amps or more) is produced with the core fully in place.

I think it would take a fairly special, heavy duty ammeter to measure 45 amps, let alone 100 amps. I don't think normal multimeters measure up to those kinds of levels, do they?

 

[shenion]

The clip-on meters can measure large currents (AC only.)

You can get shunts to measure large currents. I.e 0.01 ohm. Then use a regular voltmeter (0.01 ohm = 10mv/amp) But these are designed for lab use and are usually high-precision. Expect to pay close to $100.

I have an old dwell/tach/volt meter for cars. It has a shunt to test alternators. Will measure up to 90A DC.

 

[Dangle_kt]

why not make the marks relative, they may not be actual AMPs, but a few equally spaced lines with numbers 1-10 next to each will help you re-find settings for each thickness. actual ampage is kind of not needed unless someone is telling you what amps to use. I'd just have a go on a load of different materials and get a "feel" for it.

 

[shenion]

That is what I do. My rod tubes have written on them:

Mid range
40-45 (dial is 0-100)
DCEP

My Airco has no current scale ,just low, med high for 5-60, 20-220, 120-475A. Hard to quantify that with acurrent as the 0-100 dial is non-linear.

 

[GeorgeB]

I think it would take a fairly special, heavy duty ammeter to measure 45 amps, let alone 100 amps. I don't think normal multimeters measure up to those kinds of levels, do they?

I think Splatfest may have been correct with his original idea. I'd never heard of a clamp meter before but they look useful. Here's one which costs £64 and measures up to 1000 amps in either AC or DC:

http://www.digital-meters.com/Tecpe...p-16141.html?gclid=CJXXx-KZ1ZICFQpeQgod_Wlw_Q

 

[SAE140]

To measure heavy DC current you can put a resistor in the output lead and then measure the voltage dropped across it.

I've got a couple of such resistors - they look for all the world like an ammeter shunt - made from seriously heavy brass with what looks like phosphor-bronze laminate inserts which have been machine-trimmed during calibration. 300A produces an output of 50mV.

Colin