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coil reverse polarity test

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weiwei2

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i would like to test whether a coil (inductor) is connected in wrong side .... how to do that?

the coil is actually on a harddisk arm (the read head).... there are two tiny pins connecting the start and end of the coil. sometimes they are connected wrongly...
 

u could detect the polarity by verifying the direction of the mag field generated when u pass current through the coil
 

you buy a new hard disk if it has been exposed to air it will never work again....
 

drunk

Monkey is not drunk. Today he is overly economical with his words.

What he means is that hard drive media are in a sealed section with an atmosphere devoid of dust particles. If you open that section there will be so many dust particles on the media from the air in your room that they will act like sand paper and ruin the read/write head. They will also block reading and writing of the media portion they are on.
 

actually i'm testing the coil of harddisk reader arm which hasn't been assembled onto harddisk. it is not my harddisk....luckily

is there anyway to build a circuit to test for this reverse polaraity?
 

inductance meter

You should buy an inductance meter. If the coils are in series properly, you will get a maximium inductance L. If they are in parallel the inductance will be about L/4. If they are in series the wrong way the inductance will be near zero. All of these values assuming high mutual inductance between the coils.
 

hallo
i dont understand any thing form this discusion :roll:
how can a coil have a polarity

thanx
 

coil polarity

An isolated coil does not, but with two the mutual inductance does have a polarity. That is why there are dots on the schematics of two coils with mutual inductance.
 

ok, i will try it out using inductance meter (haven't got such a meter yet) and tried put the result here when i got it

but i did see a circuit just using some comparators to do that detection. i don't know and don't understand what is it the circuit is doing. any clue on this?
 

home made meter

The circuit was probably a home made inductance meter. You make a RL circuit with a voltage and measure the time for half voltage is one way.
 

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