Question about behaviour of stepper motors in manual mode

hello

I am new to the world of 3 printers.
I tried to use ramps with arduino and marlin firmware, and I began to give a command in manual mode to one of steppers. I tried both repetier host and pronterface.
I used my multimeter to see the current that one of phases of the stepper will draw.
I found that, the motor nearly does not draw significant current while rotation, and it usually draws a sigificant current when stops!
actually, when it stops, one time it drew 0.8 amps with making noise, and another time 1.25 amps with making noise(nothing changed, test is at no load), and even some times the meter gives me 0 with no noise at all, so the stepper draws 0 current at standstill.
I do not understand, is this correct? what is the correct behaviour of stepper that I send a manual command to it using repetier or pronterface?

What you measured seems normal to me: depending on the position, one coils gets more and the other less current (at full step positions one coil has all the current and the other none). But it's not a good idea to measure the current through the coils, its not very meaningful and if you somehow loose the connection you can easily damage the driver.

thanks for replying.

but I want to ask, Why in stand still, there are sometimes noise, and other times no noise?
If I understand correctly, if the motor has no noise at standstill, this means that the driver is idle and consumes no current and will not heat up, also this means less heating to the motor , is this true?
is is a bug in marlin code? why sometimes there is noise and other times no? can not I make the motor consumes no current at standstill (like DC motors for example) ?

I am not an expert, but I assume that the amount and type noise you hear when the motor is not moving depends on the current and the exact position in which the coils have to keep the axis balanced in between the full-step positions. But even when there is no noise, as long as the stepper motor is enabled, there will always flow current at least in one coil.

The stepper motors need the current when not moving to keep the position at the current position. You will note that if you try moving the motor by hand, it takes a lot of force while the motor is enabled. If you cut off the current altogether, the motor axis will jump to the nearest full step position, but it now can be easily moved by hand. You can disable the motors between moves in the firmware (macros DISABLE_[XYZ] in Marlin) - I use that sometimes, but only for the Z-axis (after making sure that my layer height is a multiple of the full-step distance).

thank you , good information to know!