This article offers a detailed introduction to head of hard disk and the number of head.
Head of hard disk is the key component to read data.
Its main role is to convert magneticinformation on hard diskto electrical signal to transmit the information outward.
Generally, the number of head on hard disk is 1 or 2.
This requires more than two heads to operate.
1.An Introduction to Number of Head
The role of head is that it can convert magneto-electricity.
The cost of head holds around 40% of the total cost of hard disk.
If people want to have breakthrough in storage per disk, they must improve head technology.
In LBA mode, the maximum number of heads can be set up to 255.
2.An Introduction to Head
Hard disk head is the key component for disk to read data.
The storage density of hard disk is largely determined by the quality of head.
Now, GMR (Giant Magneto Resistive) is commonly used.
The relative change of magnetic field of GMR can cause changes of large resistance value.
This can achieve higher storage densities.
Head is made by made of coils winding on the magnetic core.
When hard disk works, head reads data by sensing the changes of magnetic field on the rotating disc.
It writes in data by changing magnetic field on disc.
Earlier head uses ferromagnetic material.
This results in its bad magnetic induction sensitivity.
So, storage per disk of the earlier hard disk is small.
The larger the storage per disk is, the lager the track density will be.
Data cant be accurately read out, if head sensitivity degree is not enough.
This results in a limited capacity.
With the development of technology, magnetic induction sensitivity and precision of head have been improved a lot.
Reading and writing functions of earlier head are together with each other.
This has a high requirement in manufacturing process and technology of head.
The characteristics of reading and writing operations are quite different from each other.
This leads to the appearance of separate heads with reading and writing function respectively.
The two heads work separately without interference to each other.
Actually, TFI head is a winding magnetic core.
The induced voltage will produce when disc passes under the winding magnetic core.
TFI reading/writing head reaches its capacity limitation, because magnetic sensitivity degree is improved while writing ability is weakened.
This will produce strong signal.
Hard disk decodes the change of strip resistance triggered by the change of magnetic field polarity.
This improves reading sensitivity of hard disk.
AMR head further improves surface density while reduces the number of components.
This makes the sensitivity degree of AMR head also has a limit.
So, the development of GMR head comes into being.
But its reading head has higher sensitivity degree to magnetic transformation on hard disk.
The number of head in hard disk is determined by the number of discs.
There are data on both sides of this disc.
So, the disc has two heads.
However, the disk with total capacity of 120 GB uses two discs.
