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This is in with my other question about components and the other question about electricity; how can I check to see how many amps are being pulled? Can I check a component at a time to make sure I'm not going over the limit, and then just add them all in together once I've summed the amps to make sure it's safe to hook everything up. The amps shouldn't change right?

What settings should my multimeter be set to? And to check how much it's pulling, do I just put the multimeter's leads on the green terminals on RAMPS 1.4?

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  • $\begingroup$ @TomvanderZanden - whilst it is technically only about how to read current draw with a multimeter, it is specifically about the current draw of a 3D printer control board, and so the many answers which have been provided may be rather useful to other 3D printer users. You make a very good point about shorting the power supply, though. $\endgroup$
    – Greenonline
    May 11 '17 at 12:37
  • $\begingroup$ @TomvanderZanden I agree with Greenonline, this may be useful to others looking to troubleshoot their 3D Printer explicitly. Therefore the context should reside in the 3D Printing network. $\endgroup$
    – tbm0115
    May 17 '17 at 16:23
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To measure amps (current), the meter has to be wired in series with the item to be measured (for this reason, ammeters are designed to have very low resistance).

This has the down-side that you have to disconnect the component to put the meter in line with it. That makes it hard to do the "check a component at a time" method you mentioned.

An ammeter measures actual current flow, so you really can't test a component for it in isolation. Components can have wildly different "current draw" depending on the situation. For example, motor current varies with torque and speed; current through a resistor varies with the voltage across it; and so on.

There are special "clamp-on" current meters that just clamp around a conductor and report the current by using induction. Very nice if you have one.

If you just want the total current the entire RAMPS board is pulling, put the ammeter between the power supply and the RAMPS power input connection(s). Be very sure not to have the meter set to read volts or ohms when you do this (it might or might not survive).

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    $\begingroup$ Also be sure the meter you use is rated for current measuring well beyond the current you think you'll see, or you'll either blow the internal fuse or destroy your meter. $\endgroup$
    – Jeff
    Jan 28 '16 at 15:43
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    $\begingroup$ A multimeter set to volts or ohms will have very large input impedance and is unlikely to be damaged in any way. You have neglected an important point of current measurement using a multimeter: you usually need to swap the probe lead over to the socket for current measuring. Most multimeters can only measure up to 10A which is less than the heated bed may draw. $\endgroup$ May 11 '17 at 8:06
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The easiest method is to use a Clamp On amp meter on either the hot or neutral of your power supply.

In most cases clamp on meters only work with AC xor DC power so you would only be able to get the reading on one side of the power supply.

Multiply this number by the voltage and you get the wattage.

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  • $\begingroup$ The power to both pairs of the (green) terminals on the RAMPS board is only D.C., so he would require (as you say) a DC Current Clap meter. $\endgroup$
    – Greenonline
    May 11 '17 at 12:27
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If you don't want to stick a multimeter on the wire, I recommend getting a kill-a-watt meter. Pretty much, you plug it into the wall, and plug the printer into the meter, and it has a little screen that shows the result.

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  • $\begingroup$ I like this idea. It sounds safer. $\endgroup$
    – leeand00
    Feb 2 '16 at 13:26
  • $\begingroup$ @leeand00 - The downside of this method, is that you would also be measuring the additional power used by the power supply (and any losses therein). Also, the current reading would not be the same as the current drawn by the RAMPS board, as the step-down transformer in the power supply will reduce the voltage to 12/24V, but, possibly, increase the current. This method works if you want to measure the total power used (including any power lost in the power supply), but will not give you accurate current reading for the RAMPS board, per se. $\endgroup$
    – Greenonline
    May 11 '17 at 12:40

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