Testing Amps or Volts with Clamp type meter?
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  1. #1

    Testing Amps or Volts with Clamp type meter?

    I have an AC/DC clamp on type Amp/Volt Meter and need to make sure a welder who is taking a test has his settings in the range to meet the WPS. He is using SMAW. I clamp the meter around the welder cable near the stinger and the readings I get are REALLY low. What am I doing wrong?

  2. #2
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    Re: Testing Amps or Volts with Clamp type meter?

    Do you have the meter set correct? AC or DC. Do you have the range set properly?

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by twinpoint View Post
    I have an AC/DC clamp on type Amp/Volt Meter and need to make sure a welder who is taking a test has his settings in the range to meet the WPS. He is using SMAW. I clamp the meter around the welder cable near the stinger and the readings I get are REALLY low. What am I doing wrong?
    I posted a question like this a few weeks back when I ran some tests on a HF 80 toaster inverter. Got 148 views, no replies. Guess no one has ever done it.

    I made sure that I used a "RMS" clamp meter for the DC current readings and clamped around the stinger cable while running beads. It's important that you use a "RMS" meter, not a run-of-the-mill clamp ammeter for correct readings.

    Ironically, the readings seemed to trend higher than the dial settings for amperage.

    http://weldingweb.com/showthread.php?t=183431

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    Re: Testing Amps or Volts with Clamp type meter?

    Be sure it is a DC ammeter. many cheaper meters only do AC amps but AC and DC volts...

    I did it testing an everlast machine .
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    Re: Testing Amps or Volts with Clamp type meter?

    Nice video SP#2. I want to try that on my welder to see what amps I usually weld at.
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    Re: Testing Amps or Volts with Clamp type meter?

    I did that video to demonstrate the fluctuation of that Everlast when welding. compared to using my powcon or V205T which stayed within 1 or 2 amps range when stick welding...
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    Re: Testing Amps or Volts with Clamp type meter?

    I can't view that video. I wish there was more on this. I've just been shopping AC/DC volt/amp clamp on meters for this very purpose. I don't weld often enough to remember the sweet zone on the dials.
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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by Stick-man View Post
    I can't view that video. I wish there was more on this. I've just been shopping AC/DC volt/amp clamp on meters for this very purpose. I don't weld often enough to remember the sweet zone on the dials.
    About the best deal for a DC amp capable one is Craftsman. they have one for $57. does up to 400 amps......http://www.sears.com/craftsman-digit...6&blockType=G6
    The meter in my video is from Zoro tools. http://www.zorotools.com/g/Clamp-On%20Ammeter/00029977/got it with a $35 promo code. like it a lot and it updates much faster than the Craftsman. I own both. the Craftsman one is in my car toolbox..
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  9. #9

    Re: Testing Amps or Volts with Clamp type meter?

    Thanks for all the information. Can you recommend a brand of "RMS" meter?

    I guess my little cheapo clamp on meter just isn't up to the task.....

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by twinpoint View Post
    Thanks for all the information. Can you recommend a brand of "RMS" meter?

    I guess my little cheapo clamp on meter just isn't up to the task.....
    This is the one I bought:

    http://www.sears.com/craftsman-profe...1&blockType=G1

    Some other mfgs. can run $200-$300.

  11. #11

    Re: Testing Amps or Volts with Clamp type meter?

    Thank You a lot for all the help!

    I really needed to get this figured out. I thought I just could use any clamp meter and now I know that is not the case.

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by shortfuse View Post

    I made sure that I used a "RMS" clamp meter for the DC current readings and clamped around the stinger cable while running beads. It's important that you use a "RMS" meter, not a run-of-the-mill clamp ammeter for correct readings.
    I'm sure you all realize that the voltage in AC signal varies constantly; it has two points in it's cycle where it's voltage is zero, another point where it is at it's maximum positive voltage and an other point where it has a maximum negative voltage. Therefore AC signals (voltage or power) are usually measured in terms of what they would equal in DC. In other words, 100 volts AC would have the same power potential as 100 volts of DC power, even though the AC signal would have higher maximum positive and negative peaks. You also have to keep in mind that not all AC signals are a pure sine wave so it can be difficult to impossible to calculate the effective voltage or power in a non-sinusoidal signal, hence the need for RMS. RMS stands for Root Mean Square and it's slightly more accurate way of measuring the effective AC voltage or power than simply using an arithmetic average. The difference between RMS and Average is usually very small and would not be noticeable in welding. Also RMS is only meaningful when dealing with a AC signal, it's completely non-applicable when talking about DC since DC has a constant level.

    Most (all that I know of) electrician type Amp-meters will only read AC amps (along with AC or DC volts). They will not read DC amps. Check your meter's specs!

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by FlaJoe View Post
    I'm sure you all realize that the voltage in AC signal varies constantly; it has two points in it's cycle where it's voltage is zero, another point where it is at it's maximum positive voltage and an other point where it has a maximum negative voltage. Therefore AC signals (voltage or power) are usually measured in terms of what they would equal in DC. In other words, 100 volts AC would have the same power potential as 100 volts of DC power, even though the AC signal would have higher maximum positive and negative peaks. You also have to keep in mind that not all AC signals are a pure sine wave so it can be difficult to impossible to calculate the effective voltage or power in a non-sinusoidal signal, hence the need for RMS. RMS stands for Root Mean Square and it's slightly more accurate way of measuring the effective AC voltage or power than simply using an arithmetic average. The difference between RMS and Average is usually very small and would not be noticeable in welding. Also RMS is only meaningful when dealing with a AC signal, it's completely non-applicable when talking about DC since DC has a constant level.

    Most (all that I know of) electrician type Amp-meters will only read AC amps (along with AC or DC volts). They will not read DC amps. Check your meter's specs!
    There are quite a few clamp ammeters out there (RMS included) that read AC and DC volts and amps as well as the other parameters such as frequency, temps, diodes, continuity, etc. As you said, you have to read the specs on the ammeters carefully. The cheaper models are usually not RMS, nor do they read DC amps.

    The readings I took with the clamp ammeter I referenced were in DC amperage mode, not voltage, and jumped around considerably, not constant. I was not measuring AC or DC voltage across the stinger lead (DCEP). DC, I realize is not a sine-wave form.

    The main reason for choosing an RMS ammeter was due to another series of threads/posts I read some time back wherein the folks measuring the amperage output of their stick welder to the stinger emphasized the use of RMS. I sure as heck was not going to buy an incorrect ammeter then have to get another. There is always the possiblilty that the folks in the other thread were just blowing smoke....but this is the internet, right and everything is true???
    Last edited by shortfuse; 11-23-2012 at 06:47 PM.

  14. #14

    Re: Testing Amps or Volts with Clamp type meter?

    I have narrowed my search to a couple units that are true RMS and will do DC amps. There are many other units that will do the job but they get up to $300 for them.

    The Sears model ($110) that was suggested a few posts back and the Fluke 337.

    The Fluke 337 are no longer made but there are plenty of good used ones on Ebay.
    http://www.fluke.com/fluke/usen/elec....htm?PID=70328

    I'm leaning towards the Fluke since I'm a tightwad and can get it cheaper, Also the resale on it will be better should I need to sell it.

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    Re: Testing Amps or Volts with Clamp type meter?

    The Amprobe one I linked to has been the best one I have owned. I have had 2 craftsman ones as well... at $95 its a good deal. google for coupon codes for zoro tools too.
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  16. #16

    Re: Testing Amps or Volts with Clamp type meter?

    Ended up buying a new Klein CL2000 for $89 on Ebay - it should do the job since it has DC Amps and is true RMS. They were $139 at Home Depot.

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by soutthpaw View Post
    About the best deal for a DC amp capable one is Craftsman. they have one for $57. does up to 400 amps......http://www.sears.com/craftsman-digit...6&blockType=G6
    The meter in my video is from Zoro tools. http://www.zorotools.com/g/Clamp-On%20Ammeter/00029977/got it with a $35 promo code. like it a lot and it updates much faster than the Craftsman. I own both. the Craftsman one is in my car toolbox..
    I have a 575A welder, so I am looking for a 600A DC meter. I think I will probably get an Extech MA640. Reasonably priced on Amazon.
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    Re: Testing Amps or Volts with Clamp type meter?

    I think when FlaJoe said electrician type meters, he was referring to a meter like the Fluke T5-1000 which has a split in the end that a wire fits into and they only read AC on the amps feature. A lot of plant electricians carry these.

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by RaptorDuner View Post
    I think when FlaJoe said electrician type meters, he was referring to a meter like the Fluke T5-1000 which has a split in the end that a wire fits into and they only read AC on the amps feature. A lot of plant electricians carry these.

    Fluke T5-1000 DMM
    In twinpoint's OP, he said he wanted to clamp the meter around the stinger lead. This would be DC output if it's a DC welder. He didn't specify the type of welder; AC or DC.

    The Fluke T5-1000 DMM only reads AC voltage/current. You need a clamp meter that has BOTH AC and DC volts and amps (amps, particularly for the welder output) if you want to read the DC output.

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by FlaJoe View Post
    Also RMS is only meaningful when dealing with a AC signal, it's completely non-applicable when talking about DC since DC has a constant level.
    I do not agree. DC is DC as long as the polarity is constant, the voltage can jump around all over the place as long as it doesn't reverse. One example is old cheap car battery chargers, basically a transformer and a rectifier bridge with no other parts meant to smooth out the voltage. You get a "pulsing" DC after rectifying AC, basically the same sine wave but with the negative waves inverted so all are positive. Add a capacitor and the voltage smooths out alot, but still with alot of ripple under load. DC in both cases, but "dirty" DC that won't work very well for anything sensitive.

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    Re: Testing Amps or Volts with Clamp type meter?

    the fluke 337 is a very good unit

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    Re: Testing Amps or Volts with Clamp type meter?

    Quote Originally Posted by twinpoint View Post
    I have an AC/DC clamp on type Amp/Volt Meter and need to make sure a welder who is taking a test has his settings in the range to meet the WPS. He is using SMAW. I clamp the meter around the welder cable near the stinger and the readings I get are REALLY low. What am I doing wrong?
    Looking at the welding machine settings doesn't show if he set it correctly?

    Taking a measurment as you suggest, assuming your test equipment is set correctly and is operating properly, will only verify if the welding machine is doing what it is set up to do. If you want to see if the weldor has set the welder correctly just look at the control panel on the machine! If there is a discrepancy between the measurements taken and the welding machine settings then some troubleshooting is needed.

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    Re: Testing Amps or Volts with Clamp type meter?

    I thought all you all were insane when you said you could measure DC amps with a clamp on meter as DC doesnt work with induction type meters but, it turns out new technology has come up with away to use a clamp on for DC. I would guess they use something similar to an electronic points ignition to chop the DC into an alternating current (alternate from DC to zero) to get them to work with an induction type meter. The old way was to break the circuit and re-connect the meter in the circuit to get amps or calculate with Ohms law. Calculating had errors due to reactance and impedence in a dynamic circuit.

    As for the RMS, as FlaJoe stated, Root Mean Square is to calculate the DC equivalent volts. It doesnt apply to DC measurements. The square root of two is 1.414. If you take 10 volts AC peak and divide by 1.414 you get 0.707 volts AC RMS. Half of 1.414 is 0.707 and its easier for me to multiply 0.707 to get RMS. I thought most meters figured that for you but maybee Im wrong. Figuring RMS is usually used when measuring AC with an oscilliscope as they show true pk to pk volts but maybee Im wrong.

    My preference for clamp-ons is the Old Amprobe. For everything else its FLUKE.

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    Re: Testing Amps or Volts with Clamp type meter?

    I would guess they use something similar to an electronic points ignition to chop the DC into an alternating current (alternate from DC to zero) to get them to work with an induction type meter
    Actually that is not correct. To measure DC current with a clamp on meter requires a "hall effect" probe. It is a way of sensing the amount of DC current. Research "Hall effect" for more info.

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    Re: Testing Amps or Volts with Clamp type meter?

    Good info davido and thanks for the correction on Hall effect as DC wont give a signal in a clamp on without it. How long have clamp ons for DC been around? Also, I have to correct my math. 10 volts AC pk-pk divided by the squre root of 2 is 7.07 volts RMS not 0.707. Another correction is; I said,"reactance (capacitor) and inductance (coil), I meant reactance and impedence can cause errors in calculating amps in a static circuit as compared to a dynamic circuit as the two can introduce more resistance.

    Lastly, are those CRAFTSMAN meters made by FLUKE?

    I think of the sine wave as a set of boobs. I want to be on the peak but I usually get at somewhere around the square root of two. Dumb joke about Bell curve, Mean average and stuf.

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