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Thread: Amp Draw-Equipment needed and directions how!

  1. #1
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    Default Amp Draw-Equipment needed and directions how!

    I would like to measure current[Amp]draw for several of my lights/batteries.

    What equipment do I need and how is it done?

    All I have is a Voltage meter. I would think more is needed?

    ,,,,,,,,Thanks

  2. #2
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    Default Re: Amp Draw-Equipment needed and directions how!

    ... is the archimedes peak

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    Flashaholic* hiuintahs's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    As you are aware, in order to make a current measurement, you have to break the circuit and put the meter in series. If you have a decent DMM, you can put the meter in current mode, move the leads to the current out jack and insert the leads between flashlight tail cap and battery. A more sophisticated route is to use a precision resistor in series with your device and then measure the voltage across the resistor and use ohms law to come up with the current. The drawback here is that you need a small resistor in most cases so as to not interfere with the operation of the device for which you are trying to measure.

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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by hiuintahs View Post
    As you are aware, in order to make a current measurement, you have to break the circuit and put the meter in series [...] .
    Not necessarily, e.g. see current clamp meters. But they're not so easy to employ in this context.

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    Flashaholic* hiuintahs's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by Gauss163 View Post
    Not necessarily, e.g. see current clamp meters. But they're not so easy to employ in this context.
    I thought about those but they don't seem to have the small current resolution.

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    Flashaholic Enderman's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Use a clamp meter like the UT210E.
    It's cheap and works great, almost all modders/testers over on the other flashlight forum have this exact model.
    Unlike a multimeter, it doesn't go in series in the circuit, so it gives more accurate readings without changing any resistance.
    All you need to do is put the clamp around one main power wire and set it to measure DC current.

  7. #7
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    Default Re: Amp Draw-Equipment needed and directions how!

    Thanks everyone.

    archimedes link helped me measure several lights by placing probe on battery and the other on the body. As the article stated if they are anodized the method presented will not work.

    I have to read more and find out the simplest method to measure current draw for my lights that are anodized and ones w/ 3 or 4 batteries.

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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by IlluminationDomination View Post
    Thanks everyone.

    archimedes link helped me measure several lights by placing probe on battery and the other on the body. As the article stated if they are anodized the method presented will not work.

    I have to read more and find out the simplest method to measure current draw for my lights that are anodized and ones w/ 3 or 4 batteries.
    You are welcome.

    That is not my article, by the way, it was written by another CPF member here.
    ... is the archimedes peak

  9. #9
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    Default Re: Amp Draw-Equipment needed and directions how!

    The numbers race back and forth for awhile until they stabilize. The longer I hold the probes on the higher the Amps get.

    I guess if I choose the highest number that would be the MAX Amp draw?

  10. #10
    Flashaholic Enderman's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Measuring with a multimeter will not give you the correct numbers at all.

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    Default Re: Amp Draw-Equipment needed and directions how!

    ^^^^

    I am sure that UT210E is more accurate.The numbers did not fluctuate back and forth. I saw them range in price from ~ $20 to $60.

    On the other hand the guy in the video struggled a lot more w/ his readings than I did. His battery seemed a lot looser, the DMM was all over the place and he was having difficulty keeping the light on.

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    Flashaholic* hiuintahs's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by Enderman View Post
    Use a clamp meter like the UT210E.
    It's cheap and works great, almost all modders/testers over on the other flashlight forum have this exact model.
    Unlike a multimeter, it doesn't go in series in the circuit, so it gives more accurate readings without changing any resistance.
    All you need to do is put the clamp around one main power wire and set it to measure DC current.
    It won't necessarily give a more accurate reading.........just depends on the system that is being tested. I have the UT210E. I bought it to measure the parasitic drain on my truck which is around 50mA..........because I didn't want to unhook the battery terminal just to occasionally check the current. The lowest setting is 2A so you would have 3 decimal place current. So that is 1mA, but it jumps all over the place. And you constantly have to zero it out. It's tough for these clamp meters to read small currents and can't read a small current like the uA of parasitic drain of electronic controlled switched lights because the resolution isn't there. It has its place but I guess it just depends on the device of which you are trying to measure the current.

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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by hiuintahs View Post
    It won't necessarily give a more accurate reading.........just depends on the system that is being tested. I have the UT210E. I bought it to measure the parasitic drain on my truck which is around 50mA..........because I didn't want to unhook the battery terminal just to occasionally check the current. The lowest setting is 2A so you would have 3 decimal place current. So that is 1mA, but it jumps all over the place. And you constantly have to zero it out. It's tough for these clamp meters to read small currents and can't read a small current like the uA of parasitic drain of electronic controlled switched lights because the resolution isn't there. It has its place but I guess it just depends on the device of which you are trying to measure the current.
    From reading OP's post it seems like he wants to measure the amp draw of his lights when they are on, not parasitic drain in microamps.
    The UT210E is great for regular flashlight amp draws, because it doesn't add anything to the circuits and therefore gives an accurate reading.
    It may not be as precise as a multimeter with 4 decimal places, but what matters here is accuracy not precision.

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    Default Re: Amp Draw-Equipment needed and directions how!

    From what it looks like, using the method shown will not test the resistance of the flashlight switch, and therefore amperage draw while in normal use is unknown.

    Could an accurate light meter and a timer be used to get relative comparisons between batteries, or emitters? Is there another way?

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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by Enderman View Post
    Use a clamp meter like the UT210E.
    It's cheap and works great, almost all modders/testers over on the other flashlight forum have this exact model.
    Unlike a multimeter, it doesn't go in series in the circuit, so it gives more accurate readings without changing any resistance.
    All you need to do is put the clamp around one main power wire and set it to measure DC current.
    Thanks for the suggestion.

    1.Can this[UT210E] device measure lights that are anodized and ones that have multiple batteries? If so, what is the method for accomplishing that?

    2. For now, is there any way w/ a DMM to measure Amp draw for lights w/ multiple batteries. Battery carriers w/ 3 or 4 batteries that are anodized?

    Thanks

  16. #16
    Flashaholic Enderman's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    You just need to put a wire somewhere that completes the circuit outside of the battery carrier and measure the current through that wire.

  17. #17
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by Enderman View Post
    You just need to put a wire somewhere that completes the circuit outside of the battery carrier and measure the current through that wire.
    Ok,,,Thanks.

    Do you know the answer to question #2?


    I was able to position the flashlight better and my readings were much more stabilized. I actually got them to stop for 5 seconds or more.

  18. #18
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    Default Re: Amp Draw-Equipment needed and directions how!

    I do not know a lot about electricity but this still baffles me.

    I was only able to test amp draw w/ my DMM. It would not check voltage anymore. So I took it apart hoping the fuse blew. It did and I replaced it and both are working now.

    How can a DMM measure Amp draw w/ a blown fuse and Not voltage?! I would think the entire DMM would be inoperable.

  19. #19
    Flashaholic* hiuintahs's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by IlluminationDomination View Post
    ..........How can a DMM measure Amp draw w/ a blown fuse and Not voltage?! I would think the entire DMM would be inoperable.
    Something doesn't add up there so not sure why.

    I've accidentally blown the fuse before. It happens when you get in a hurry and forget to move the leads off of the current jack on the DMM before you move the dial over and make a voltage measurement. I'm not sure what brand of DMM you have but the Fluke I have will beep at you if you move the dial while the leads are still in the current measurement jack. When measuring voltage, the meter is a high impedance to that voltage source and will not draw much current at all from the measuring source. When measuring current the meter is a low impedance (ie: through a small sense resistor in the meter). Thus its necessary to have a fuse inline to protect the workings of the meter. However my experience is that with a blown fuse, voltage measurements still works but the current won't.

    But if its working now with fuse replaced, I wouldn't worry about it.

    What light are you having trouble measuring the current on? A picture of your setup?
    Last edited by hiuintahs; 02-12-2018 at 12:51 PM.

  20. #20
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    Default Re: Amp Draw-Equipment needed and directions how!

    The only lights I had trouble with are the anodized ones. In the link archimedes provided it stated it would NOT work w/ anodized threads.

    LOL,,,I think I just got my answer as to why it worked w/ Amp draw and NOT Voltage. At bottom of DMM on Left[10A] it states "Unfused" and on Right it states "Fused". The Two holes on Right are for my Voltage readings.


  21. #21
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    Default Re: Amp Draw-Equipment needed and directions how!

    I saw a video of a guy checking Amp draw w/ a DMM. He had his own custom[thicker] wires w/ the tips soldered. He got an increase of ~ 1amp compared to using the leads that come w/ the DMM. He said the increase was because the leads have little indents/notches at the end which restrict the current flow.Similar concept as a bottle neck restricting water flow.

    If that is true why don't they make the leads completely solid instead of having the indents/notches at the end?

    Thanks

  22. #22
    Flashaholic* hiuintahs's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Even with anodized threads, the flashlight tube should still be bare aluminum on the tube end, right? That is where I make my connection point with one of the DMM leads.

  23. #23
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by hiuintahs View Post
    Even with anodized threads, the flashlight tube should still be bare aluminum on the tube end, right? That is where I make my connection point with one of the DMM leads.
    That is not the case w/ my U21 and M2X.

  24. #24
    Flashaholic* hiuintahs's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Olight M2X-UT? I don't have one but was looking at Going Gear's review and I could see bare aluminum on the end of the battery tube where the tail cap would make electrical contact once screwed all the way on.

  25. #25
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    Default Re: Amp Draw-Equipment needed and directions how!

    ^^^

    You are correct. The first time I was down too far on the threads. The second time I went inside the tub[anodized]. The Third time was the charm.

  26. #26

    Default Re: Amp Draw-Equipment needed and directions how!

    A problem with measuring flashlight current is that any ammeter drops the voltage, so you're not measuring the current at the actual voltage the flashlight sees when operating normally. Sometimes it doesn't make much difference, but in direct drive lights and a lot of single 18650 cell lights, it can. If you can get sufficient resolution, use the 10A DMM scale rather than a lower current scale. That will reduce the voltage drop. But I made up a meter with even less voltage drop:



    The wire is about 7 inches of #22 copper wire connected, as you can see, directly between the probe tips. The probes go to an inexpensive DMM set to the lowest mV scale. Connect the probes to the device under test like you would for any current measurement. The scale factor is 10mV/amp, or 100mA/mV. This is a smaller drop than a typical DMM but of course the resolution isn't adequate for low current measurements. If you do something similar, make sure the wires solidly connect right at the probe tips. You can use a measured voltage and known resistance to adjust the exact wire length (for example, 5.0 volts and a 5 ohm resistor which should measure 10mV for the 1A that's flowing).

    c_c

  27. #27
    Flashaholic* hiuintahs's Avatar
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    Default Re: Amp Draw-Equipment needed and directions how!

    Good info CC. I once had a class in college titled "Electronic Measurement". There actually is more to making measurements than meets the eye. Some times it matters and other times the error associated with hooking up test equipment is so small that it doesn't matter. One just has to understand how their test equipment may be affecting the circuit under test and whether that error matters or not.

  28. #28
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by IlluminationDomination View Post
    I saw a video of a guy checking Amp draw w/ a DMM. He had his own custom[thicker] wires w/ the tips soldered. He got an increase of ~ 1amp compared to using the leads that come w/ the DMM. He said the increase was because the leads have little indents/notches at the end which restrict the current flow.Similar concept as a bottle neck restricting water flow.

    If that is true why don't they make the leads completely solid instead of having the indents/notches at the end?

    Thanks
    Does anyone know WHY DMM leads are not solid?

    It seems that CC'S post verifies what the guy in the video proposed even though he used wire w/ soldered tips.

  29. #29
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by IlluminationDomination View Post
    Does anyone know WHY DMM leads are not solid?
    Usual DMM's must have a very good isolation (The can be used at 600-1000V) and the probe wires are made for that.
    A probe marked CAT IV 1000V must handle up to 12000V peak!
    My website with battery, charger, usb reviews, comparisons & information: https://lygte-info.dk/
    Latest addition is multimeter reviews

  30. #30
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    Default Re: Amp Draw-Equipment needed and directions how!

    Quote Originally Posted by HKJ View Post
    Usual DMM's must have a very good isolation (The can be used at 600-1000V) and the probe wires are made for that.
    A probe marked CAT IV 1000V must handle up to 12000V peak!
    Ok Thanks. I do not totally understand that! Does that mean if they are solid the isolation will be bad?

    What is the meaning and definition of "Isolation" in this application?

    Thank you

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