Measurement apparatus for use in recording unit provided with control means for controlling write and read parameters

The invention is directed toward a measuring apparatus for measuring performance characteristics of a recording unit including a recording medium on which one track is divided into a plurality of sectors. The measuring apparatus includes a writing means for writing a write signal with a write parameter, a first control means for changing the write parameter value for respective sectors, a reading means for reading out the write signal written by the writing means with a read parameter and measuring the read-out write signal as a read signal, and a second control means for controlling the read parameter so as to produce predetermined read parameter values for respective sectors.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a measuring apparatus for use in a
 recording unit, in particular, to a measuring apparatus for measuring
 performance characteristics of a recording unit including a recording
 medium of a hard disk, a floppy disk, or an optical disk such as CD, DVD,
 a magneto-optical disk (of ROM, write once type, rewriting type) or the
 like and components such as a head for recording a data signal on the
 above recording medium and the like.
 2. Description of the Prior Art
 Upon testing either a fixed type magnetism fixture magnetic disk drive unit
 (referred to as a hard disk unit hereinafter) for driving a hard disk, the
 above hard disk, or a magnetic head, there is the practice of evaluating
 the performance characteristics of the above hard disk, the testing
 process includes the following steps:
 (a) inserting a spindle into a center hole of the hard disk and supporting
 the magnetic head so as to electromagnetically couple the magnetic head
 with the surface of the hard disk in a non-contact manner;
 (b) executing either a data writing process or a data reading process on
 the hard disk by means of the magnetic head while rotating the spindle by
 means of a spindle motor; and
 (c) evaluating the performance characteristics of the hard disk unit
 including the hard disk.
 As performance evaluation items, the following ones can be enumerated. The
 performance evaluation items includes the followings:
 (a) a track average signal amplitude (Track Averaged Amplitude: referred to
 as a TAA hereinafter);
 (b) an asymmetry of a signal amplitude;
 (c) a pulse width (PW);
 (d) an asymmetry of a pulse width;
 (e) a base line;
 (f) a non-linear type bit shift amount (Non-linear Transition bit shift:
 NLTS);
 (g) an overwrite characteristic (OverWrite: OW);
 (h) a bit error rate (Bit Error Rate: BER);
 (i) a margin, and so on.
 The evaluation items of the TAA for a read signal from the hard disk are
 shown in FIG. 10.
 When evaluating the performance of a hard disk, it is required to set
 parameters for measurement, and the parameters includes the followings:
 (a) a position of a magnetic head (referred to as a head position
 hereinafter);
 (b) a head angle (skew);
 (c) a spindle rotation speed;
 (d) a signal frequency;
 (e) a write data pattern;
 (f) a write current amount;
 (g) a write compensation amount (concretely, a amount of compensation for
 compensating for the write change timing);
 (h) an MR (Magnetic Resistance) head bias current, and so on.
 In this case, the signal frequency, the write data pattern, the write
 current amount, the write compensation amount, the head position and the
 MR head bias current are write parameters for the hard disk, while the
 head position, the head angle and the MR head bias current are read
 parameters for the hard disk.
 A procedure in measuring the above evaluation items has a sequence of
 parameter setting, writing onto a disk, reading out and evaluating the
 characteristics of the read signal. FIG. 11 shows signal waveforms of a
 write signal and a read signal. Conventionally, it has been a common
 practice to obtain a parameter dependency of the measured values of the
 evaluation items by changing set values of the above-mentioned parameters
 in small steps and repetitively executing a similar measurement.
 For example, FIG. 12 shows a dependency of the TAA on a write current
 amount Iw. According to the conventional technique, such a measurement has
 been executed by writing data with fixed one parameter for one rotation of
 the disk when the spindle is rotated by one turn, and reading out the
 written data during another turn, thereby obtaining the measurement data
 for one point in FIG. 12. By repeating this sequence a plurality of times
 while changing the parameter, a graph as shown in FIG. 12 is obtained
 according to the measuring method based on the conventional technique
 (referred to as a first prior art hereinafter). That is, according to the
 conventional technique, one parameter has been set per one revolution of
 the track.
 There is sometimes such a case that the state of a read element is
 disadvantageously changed by a magnetic field in the writing stage, then
 consequently, this leads to an unstable characteristic (referred to as
 instability hereinafter). This phenomenon may be a kind that occurs only
 once per several times or another kind that occurs as a variation every
 measurement. Therefore, in measuring such a characteristic, it is a common
 practice to repeat the write and read operations many times, and then
 statistically evaluate the measured values of read signals. When measuring
 the above-mentioned instability by a conventional technique (referred to
 as a second prior art hereinafter), statistic data including the average
 value and the variance of the measured value data are obtained, as shown
 in FIG. 13, by executing a plurality of times, a process including the
 steps of, first of all, writing desired data on the whole track of the
 disk, writing data which will be abandoned for a part of the track, and
 thereafter reading out the data on the rest of the track.
 The above-mentioned prior art measuring method and measuring apparatus have
 had such a problem that the measuring time is relatively long.
 Furthermore, when executing the measurement by switching the measurement
 item upon evaluating the performance characteristics of a hard disk, it
 takes much measuring time according to the prior art methods in an attempt
 at viewing the influences on the parameters requiring a significantly long
 time for convergence. As the parameters requiring a significantly long
 time for convergence, there can be enumerated the frequency, the head
 position and so on. For example, FIG. 21 shows a relationship between the
 head position and the read signal amplitude, where the relationship is
 called the track profile. Such a measurement (referred to as a third prior
 art hereinafter) takes a long time for moving the head position as
 compared with that of the rotation of the spindle, and this leads to such
 a problem that the measuring time is elongated.
 SUMMARY OF THE INVENTION
 An essential object of the present invention is therefore to provide a
 measuring apparatus for use in a recording unit, capable of measuring the
 performance characteristics of a recording unit including a recording
 medium at a higher speed than that of the prior arts.
 In order to achieve the above-mentioned objective, according to one aspect
 of the present invention, there is provided a measuring apparatus for use
 in a -recording unit, for measuring performance characteristics of said
 recording unit including a recording medium on which one track is divided
 into a plurality of sectors, said measuring apparatus comprising:
 writing means for writing a write signal with a write parameter value
 changed for respective sectors; and
 reading means for reading out the write signal written by said writing
 means, with predetermined read parameters for respective sectors, and
 measuring the read-out write signal as a read signal.
 According to another aspect of the present invention, there is provided a
 measuring apparatus for use in a recording unit, for measuring performance
 characteristics of said recording unit including a recording medium on
 which one track is divided into a plurality of sectors, said measuring
 apparatus comprising:
 writing means for writing a write signal with predetermined write
 parameters for respective sectors; and
 reading means for reading out the write signal written by said writing
 means, with read parameter values changed for respective sectors, and
 measuring the read-out write signal as a read signal.
 According to a further aspect of the present invention, there is provided a
 measuring apparatus for use in a recording unit, for measuring performance
 characteristics of said recording unit including a recording medium on
 which one track is divided into a plurality of sectors, said measuring
 apparatus comprising:
 first writing means for writing a write signal with a predetermined write
 parameter for respective sectors;
 first reading means for reading out the write signal written by said first
 writing means, with predetermined read parameters for respective sectors,
 and measuring the read-out write signal as a reference read signal;
 second writing means for writing a write signal with a write parameter
 value changed for respective sectors;
 second reading means for reading out the write signal written by said
 second writing means, with predetermined read parameters for respective
 sectors, and measuring the read-out write signal as a measured read
 signal; and
 correctively calculating means for correctively calculating the measured
 read signal measured by said second reading means, according to a
 predetermined correctively calculating method based on the reference read
 signal measured by said first reading means, and outputting a correctively
 calculated measured read signal.
 According to a still further aspect of the present invention, there is
 provided a measuring apparatus for use in a recording unit, for measuring
 performance characteristics of said recording unit including a recording
 medium on which one track is divided into a plurality of sectors, said
 measuring apparatus comprising:
 first writing means for writing a write signal with predetermined write
 parameters for respective sectors;
 first reading means for reading out the write signal written by said first
 writing means, with predetermined read parameters for respective sectors,
 and measuring the read-out write signal as a reference read signal;
 second reading means for reading out the write signal written by said first
 writing means, with a read parameter value changed for respective sectors,
 and measuring the read-out write signal as a measured read signal; and
 correctively calculating means for correctively calculating the measured
 read signal measured by said second reading means, according to a
 predetermined correctively calculating method based on the reference read
 signal measured by said first reading means, and outputting a correctively
 calculated measured read signal.
 According to a still more further aspect of the present invention, there is
 provided a measuring apparatus for use in a recording unit, for measuring
 performance characteristics of said recording unit including a recording
 medium on which one track is divided into a plurality of sectors, said
 measuring apparatus comprising:
 measuring means for measuring a read-out write signal as a read signal by,
 for respective sectors, writing a write signal and thereafter reading out
 a written write signal.
 According to a further aspect of the present invention, there is provided a
 measuring apparatus for use in a recording unit, for measuring performance
 characteristics of said recording unit including a recording medium having
 at least one track, said measuring apparatus comprising:
 writing means for writing a write signal while continuously changing a
 write parameter for one track; and
 reading means for reading-out the write signal written by said writing
 means, with a predetermined read parameter, and measuring the read-out
 write signal as a read signal.
 According to a still further aspect of the present invention, there is
 provided a measuring apparatus for use in a recording unit, for measuring
 performance characteristics of said recording unit including a recording
 medium having at least one track, said measuring apparatus comprising:
 writing means for writing a write signal with a predetermined write
 parameter for one track; and
 reading means for reading out the write signal written by said writing
 means while continuously changing a read parameter for one track, and
 measuring the read-out write signal as a read signal.
 According to a still more further aspect of the present invention, there is
 provided a measuring apparatus for use in a recording unit, for measuring
 performance characteristics of said recording unit including a recording
 medium having at least one track, said measuring apparatus comprising:
 first writing means for writing a write signal with a fixed write parameter
 for one track;
 first reading means for reading out the write signal written by said first
 writing means, with a predetermined read parameter and measuring the
 read-out write signal as a reference read signal;
 second writing means for writing a write signal while continuously changing
 a write parameter for one track;
 second reading means for reading out the write signal written by said
 second writing means, with a predetermined read parameter, and measuring
 the read-out write signal as a measured read signal; and
 correctively calculating means for correctively calculating the measured
 read signal measured by said second reading means, according to a
 predetermined correctively calculating method based on the reference read
 signal measured by said first reading means, and outputting a correctively
 calculated measured read signal.
 According to a more still further aspect of the present invention, there is
 provided a measuring apparatus for use in a recording unit, for measuring
 performance characteristics of said recording unit including a recording
 medium having at least one track, said measuring apparatus comprising:
 first writing means for writing a write signal with a fixed write parameter
 for one track;
 first reading means for reading out the write signal written by said first
 writing means, with a predetermined read parameter and measuring the
 read-out write signal as a reference read signal;
 second reading means for reading out the write signal written by said first
 writing means while continuously changing a read parameter for one track,
 and measuring the read-out write signal as a measured read signal; and
 correctively calculating means for correctively calculating the measured
 read signal measured by said second reading means according to a
 predetermined correctively calculating method based on the reference read
 signal measured by said first reading means, and outputting a correctively
 calculated measured read signal.
 According to a further aspect of the present invention, there is provided a
 measuring apparatus for use in a recording unit, for measuring performance
 characteristics of said recording unit including a recording medium on
 which one track is divided into a plurality of sectors, said measuring
 apparatus comprising:
 writing means for writing a write signal with a write parameter of an item
 changed for respective sectors; and
 reading means for reading out the write signal written by said writing
 means, with a predetermined read parameter for respective sectors, and
 measuring the read-out write signal as a read signal.
 According to a still further aspect of the present invention, there is
 provided a measuring apparatus for use in a recording unit, for measuring
 performance characteristics of said recording unit including a recording
 medium on which one track is divided into a plurality of sectors, said
 measuring apparatus comprising:
 trigger generating means, in response to an index signal generated every
 one turn of said recording medium, for outputting or not outputting one
 index trigger signal, or for multiplying the index signal, generating and
 outputting or not outputting a plurality of sector trigger signals
 corresponding to the plurality of sectors; and
 at least one control means, in response to either the index trigger signal
 or the plurality of sector trigger signals outputted from said trigger
 generating means, for executing either one of a process of writing a write
 signal and a process of reading out the write signal.
 According to a still more further aspect of the present invention, there is
 provided a measuring apparatus for use in a recording unit, for measuring
 performance characteristics of said recording unit including a recording
 medium on which one track is divided into a plurality of sectors, said
 measuring apparatus comprising:
 at least one control means having first and second input ports and
 switching means,
 wherein said switch means switches over between an index signal generated
 every one turn of said recording medium and a plurality of sector trigger
 signals generated so as to correspond to the plurality of sectors based on
 the index signal, and selectively outputs or does not output a switched
 signal,
 wherein the index signal is inputted to said first input port, and a signal
 outputted from said switch means is inputted to said second input port,
 and
 wherein said control means controls the selective switching of said
 switching means based on the index signal inputted to said first input
 port, and executes either one of a process of writing a write signal or a
 process of reading out the write signal based on the signal inputted to
 said second input port.
 According to the present invention, the performance characteristics of the
 recording medium can be measured at a higher speed than that of the prior
 art.
 Further, when the correctively calculating means is further provided in the
 above-mentioned measuring apparatus, the measured value can be properly
 corrected and more correct measured value can be obtained.
 Further, when the statistically calculating means is further provided in
 the above-mentioned measuring apparatus, statistically processing the
 measured value can be properly performed and more correct measured value
 can be obtained. Furthermore, there can be obtained calculation results of
 the statistical processing in which the evaluation of the variation in the
 calculation results thereof is influenced by the average value for
 respective sectors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Preferred embodiments according to the present invention will be described
 below with reference to the attached drawings.
 A measuring apparatus for a recording unit including a recording medium of
 a hard disk and components such as a magnetic head for recording a data
 signal on the above recording medium according to a preferred embodiment
 of the present invention will be described below with reference to the
 drawings.
 First Preferred Embodiment
 The measuring apparatus for use in the recording unit according to a first
 preferred embodiment of the present invention is characterized in that, as
 shown in FIG. 17, a higher-speed measurement than that of the prior arts
 is achieved by dividing one track 1t on a hard disk into, for example, ten
 sectors 1s and executing a measurement with a parameter value changed for
 respective sectors 1s, i.e., executing a measurement so that one
 measurement is completed for each sector 1s. Upon measuring the dependency
 characteristic of each performance evaluating item when the parameter
 value is changed, a write parameter (e.g., a write current Iw) is changed
 for respective sectors in a time interval for one revolution of the disk
 with the read parameter value fixed as shown in FIG. 14 or a read
 parameter (e.g., MR head bias current Ib) is changed with the write
 parameter value fixed as shown in FIG. 15.
 Furthermore, due to such an arrangement that the sectors are arranged in
 different physical positions in the hard disk, a non-uniformity of the
 characteristics of the hard disk causes an error in the measured value.
 For the purpose of compensating for this, a more correct measured value
 can be obtained by using the measured value obtained with the fixed
 parameter for respective sectors (where the fixed parameter is the write
 parameter or the read parameter) as a reference value or a reference
 signal, and correcting a measured value obtained with the parameter
 changed for respective sectors (where the parameter to be changed is the
 read parameter or the write parameter) through collating or checking the
 measured value with the above reference value.
 That is, concretely speaking, a write signal is written with a write
 parameter fixed for respective sectors, and thereafter, the write signal
 is read out with a read parameter fixed for respective sectors to measure
 the read-out signal as a reference read signal having a reference value.
 In order to measure the read-out signal as a reference read signal having
 a reference value, next, the write signal is written with a write
 parameter value changed for respective sectors, and thereafter, the write
 signal is read out with the read parameter fixed for respective sectors.
 Thereafter, correction is executed by a predetermined correcting method
 based on the reference read signal having the reference value and the
 measured read signal having the-measured value, then, the measured value
 obtained after the correction, namely, the corrected value is calculated
 by a main controller 20 and is outputted to a CRT display 22 or a printer
 23 (See FIG. 1).
 Otherwise, the write signal is written with a write parameter fixed for
 respective sectors, and thereafter, the write signal is read out with a
 read parameter fixed for respective sectors to measure the read-out signal
 as a reference read signal having a reference value. Next, the write
 signal is read out with a read parameter value changed for respective
 sectors. Then, correction is executed by a predetermined correcting method
 based on the reference read signal having the reference value and the
 measured read signal having the measured value, and the measured value
 obtained after the correction, namely, the corrected value is calculated
 by the main controller 20, and then, is outputted to the CRT display 22 or
 the printer 23 (See FIG. 1).
 As a method for calculating the measured value obtained after the
 correction, as shown in Table 1, there is a method of executing a division
 calculation which is dividing the reference value measured with the fixed
 parameter by the measured value, and using the result of the division
 calculation as a corrected measured value. However, the calculating
 formula of the present invention is not limited to this.
 TABLE 1
 Sector No. 1 2 3 4 . . . N
 Reference R.sub.1 R.sub.2 R.sub.3 R.sub.4 . . . R.sub.N
 Value
 Measured M.sub.1 M.sub.2 M.sub.3 M.sub.4 . . . M.sub.N
 Value
 Measured M.sub.1 /R.sub.1 M.sub.2 /R.sub.2 M.sub.3 /R.sub.3 M.sub.4
 /R.sub.4 . . . M.sub.N /R.sub.N
 Value After
 Correction
 FIG. 1 is a block diagram showing a construction of a spin stand 100 and a
 measuring apparatus 200 for the spin stand 100 according to a preferred
 embodiment of the present invention. The measuring apparatus 200 shown in
 FIG. 1 is constructed as follows.
 Referring to FIG. 1, one Index signal is outputted from an index sensor 5
 for one revolution of a hard disk 1 when a spindle 2 is rotated by one
 revolution, while a trigger distribution module 30 generates one Index
 trigger signal (alternately referred to as an Index signal hereinafter) in
 response to the Index signal or a plurality of Sector trigger signals
 (alternately referred to as a Sector signal, and the Index trigger signal
 and the Sector trigger signal collectively referred to as a trigger
 signal, hereinafter) corresponding to the sectors of the disk 1, and then,
 outputs the same signals to a write controlling module 31, a read
 controlling module 32, and a head position controlling module 33,
 respectively. The write controlling module 31 executes a write controlling
 process as shown in FIG. 6 in response to the trigger signal, thereby
 executing a writing process for measurement of the hard disk 1. The read
 controlling module 32 executes a read control process as shown in FIG. 7
 in response to the trigger signal, thereby executing a reading process for
 measurement of the hard disk 1. The head position controlling module 33
 executes a head position control process as shown in FIG. 8 in response to
 the trigger signal, thereby executing a head position control process for
 measurement of the hard disk 1.
 The spin stand 100 shown in FIG. 1 is mainly provided with the following
 four components:
 (a) a spindle 2 for supporting the hard disk 1, a spindle motor 3 for
 driving the spindle to rotate the same, and a spindle motor driving
 circuit 11 for controlling the spindle motor 3;
 (b) a head positioning control mechanism comprising a head position control
 mechanism 13;
 (c) a write and read circuit 14; and
 (d) an index sensor 5.
 In this case, the spindle 2 is inserted into a center hole 1h of the hard
 disk 1 which serves as a magnetic recording medium so as to support the
 hard disk 1, and then, the spindle motor 3 is connected to the spindle 2.
 With the rotation of the spindle motor 3, the spindle 2 is rotated to
 rotate the hard disk 1. In this case, when the spindle 2 is rotated to
 rotate the hard disk 1, one Index signal is detected and generated per
 rotation by the index sensor 5, and the Index signal is outputted to the
 trigger distribution module 30 of the measuring apparatus 200. The
 rotation of the spindle motor 3 is controlled by the main controller 20,
 and its rotation speed is normally unchanged once it is set.
 The above-mentioned head positioning control mechanism is mainly divided
 into two sections. One is a rough positioning mechanism comprised of an
 X-Y stage or the like, and the other is a fine positioning mechanism
 comprised of a piezoelectric-stage or the like. Although the rough
 positioning mechanism is not shown because it has no direct relation to
 the present invention, the rough positioning mechanism is controlled by
 the main controller 20. The head position control mechanism 13 shown in
 FIG. 1 indicates the above-mentioned fine positioning mechanism, and it
 operates to finely adjust the position of a magnetic head 4 required for
 measurement of a track profile and so on. The operation of the head
 position control mechanism 13 is controlled by the head position
 controlling module 33. In this case, the magnetic head 4 is supported so
 as to move in a radial direction, in a direction perpendicular to the
 radial direction and approximately in a vertical direction relative to the
 track of the hard disk 1 so that the magnetic head 4 can be
 electromagnetically coupled with the surface of the hard disk 1 in a
 non-contact manner. The position of the magnetic head 4 is controlled by
 the above-mentioned head position control mechanism 13 connected to the
 magnetic head 4.
 The write and read circuit 14 receives a write signal and a control signal
 from the read controlling module 32 and the write controlling module 31 of
 the measuring apparatus 200, and then, executes a predetermined operation
 as described in detail later.
 The measuring apparatus 200 is roughly provided with the trigger
 distribution module 30, the write controlling module 31, the read
 controlling module 32, and the head position controlling module 33 in
 addition to the main controller 20 for controlling the operations of the
 controlling modules 30 to 33, a keyboard 21 which serves as an input
 means, and the CRT display 22 and the printer 23 which serve as output
 means. The controlling modules 30 to 33 are connected to the main
 controller 20 of the measuring apparatus 200 via a bus 34, and the main
 controller 20 starts its operation according to designation data issued by
 an operator from the keyboard 21 connected to the main controller 20 so as
 to control the controlling modules 30 to 33, execute the above-mentioned
 correcting or compensating process based on the data of measurement
 results outputted from the read controlling module 32, display the data of
 the measurement results and the data obtained after the correcting or
 compensating process on the CRT display 22, and output the data to the
 printer 23, thereby printing the data.
 The write controlling module 31 generates not only a write signal but also
 a write control signal including the setting of a write current, a write
 timing signal and so on, and then, outputs these signals to the write and
 read circuit 14. The write signal is subjected to a modulation process or
 the like if necessary in the write and read circuit 14, and then, a
 processed write signal is written into the hard disk 1 via the magnetic
 head 4. In this stage, a predetermined write parameter value is given to
 the write and read circuit 14 by the inputted write control signal.
 The read controlling module 32 not only receives a read signal inputted
 from the magnetic head 4 via the write and read circuit 14, but also
 generates a read control signal of MR bias current setting, read timing
 and so on required for reading out, and then, outputs these signals to the
 write and read circuit 14. In this case, the read signal from the magnetic
 head 4 is subjected to an amplifying process and so on if necessary in the
 write and read circuit 14, and then, a processed read signal is inputted
 to the read controlling module 32. A predetermined read parameter value is
 given to the write and read circuit 14 by the read control signal.
 FIG. 2 is a block diagram showing a construction of the trigger
 distribution module 30 shown in FIG. 1.
 Referring to FIG. 2, the Index signal from the trigger distribution module
 30 is inputted to the controller 40 and a frequency multiplier 42, and
 then, in response to the inputted Index signal, the controller 40
 generates selecting signals Select 1, Select 2, . . . , Select N for
 executing switching between switches over SW1a, SW2a, SW3a, . . . and the
 control of turning on and off switches SW1b, SW2b, SW3b, . . . with
 reference to operation processing data of a reference table stored in the
 reference table memory 41, and then, outputs these signals to the switches
 SW1a, SW1b, SW2a, SW2b, SW3a, SW3b, . . . The Index signal is outputted as
 a trigger signal OUT1 to the write controlling module 31 via the a-contact
 of the switch SW1a and the switch SW1b, and further, the Index signal is
 outputted as a trigger signal OUT2 to the read controlling module 32 via
 the a-contact of the switch SW2a and the switch SW2b. Further, the Index
 signal is outputted as a trigger signal OUT3 to the head position
 controlling module 33 via the a-contact of the switch SW3a and the switch
 SW3b.
 The frequency multiplier 42 multiplies the frequency of the inputted Index
 signal by, for example, ten to generate a Sector signal corresponding to
 each sector 1s obtained after the multiplication, and then, outputs the
 Sector signal as the trigger signal OUT1 to the write controlling module
 31 via the b-contact of the switch SW1a and the switch SW1b. Further, the
 Sector signal is outputted as the trigger signal OUT2 to the read
 controlling module 32 via the b-contact of the switch SW2a and the switch
 SW2b. Further, the Sector signal is outputted as the trigger signal OUT3
 to the head position controlling module 33 via the b-contact of the switch
 SW3a and the switch SW3b.
 FIG. 3 is a block diagram showing a construction of the write controlling
 module 31 shown in FIG. 1.
 Referring to FIG. 3, a controller 50 is a control circuit which controls
 the operation of the write controlling module 31 and is connected to the
 main controller 20 via the bus 34. In response to the trigger signal OUT1,
 with reference to the operation processing data of the reference table
 stored in a reference table memory 52, the controller 50 controls the
 followings:
 (a) a parameter setting section 51, which is provided with a D/A
 (digital-to-analog) converter (not shown) for setting write parameters
 such as a write current, and a timer (not shown) for determining the
 measurement time, and which controls the operation of a write control
 executing section 53, and
 (b) the write control executing section 53 which is connected to the write
 and read circuit 14,
 thereby executing a write controlling process shown in FIG. 6 and executing
 a writing process for the spin stand 100.
 FIG. 4 is a block diagram showing a construction of the read controlling
 module 32 shown in FIG. 1.
 Referring to FIG. 4, a controller 60 is a control circuit which controls
 the operation of the read controlling module 32 and is connected to the
 main controller 20 via the bus 34. In response to the trigger signal OUT2,
 with reference to the operation processing data of the reference table
 stored in a reference table memory 62, the controller 60 controls the
 followings:
 (a) a parameter control section 61, which is provided with a D/A converter
 (not shown) for setting the read parameter and a timer (not shown) for
 determining the measurement time, and which controls the operation of a
 read control executing section 63, and
 (b) the read control executing section 63 connected to the write and read
 circuit 14,
 thereby executing a read control process shown in FIG. 7 and executing a
 reading process for the spin stand 100.
 FIG. 5 is a block diagram showing a construction of the head position
 controlling module 33 shown in FIG. 1.
 Referring to FIG. 5, a controller 70 is a control circuit which controls
 the operation of the head position controlling module 33 and is connected
 to the main controller 20 via the bus 34. In response to the trigger
 signal OUT3, with reference to the operation processing data of the
 reference table stored in a reference table memory 71, the controller 70
 controls the head position control mechanism 13 via the bus 34, thereby
 executing the head position control process shown in FIG. 8 and executing
 the control process of the position of the magnetic head 4 for the spin
 stand 100.
 FIG. 6 is a flowchart showing a write controlling process which is executed
 by the write controlling module 31 shown in FIG. 3.
 Referring to FIG. 6, first of all, in step S1, the initial values of the
 parameters are read out from the reference table memory 52 and then are
 set to the parameters, and waiting is effected until a trigger signal is
 inputted in step S2. When the trigger signal is inputted (YES in step S2),
 a writing process is executed in step S3. It is decided in step S4 whether
 or not the writing process is completed, and the writing process of step
 S3 is executed until the completion of the writing process. When the
 writing process is completed (YES in step S4), the program flow proceeds
 to step S5, and then, it is decided whether or not there is the next
 writing process. When there is no next writing process (No in step S5),
 then the write controlling process is completed. When there is the next
 writing process (YES in step S5), the next parameter values are read out
 from the reference table memory 52 and then set to the parameters at step
 S6, and thereafter, the program flow returns to step S2 to repeat the
 above-mentioned processes.
 FIG. 7 is a flowchart showing a read control process which is executed by
 the read controlling module 32 shown in FIG. 4.
 Referring to FIG. 7, first of all, in step S11, the initial values of the
 parameter values are read out from the reference table memory 62 and then
 are set to the parameters, and waiting is effected until a trigger signal
 is inputted in step S12. When the trigger signal is inputted (YES in step
 S12), a measuring process for the reading is executed in step S13. It is
 decided in step S14 whether or not the measuring process is completed, and
 the measuring process of step S13 is executed until the completion of the
 process. When the measuring process is completed (YES in step S14), the
 program flow proceeds to Step S15, and then, It is decided whether or not
 there is the next measuring process. When there is no next measuring
 process (NO in step S15), the read control process is completed. When
 there is the next measuring process (YES in step S15), the next parameter
 values are read out from the reference table memory 62 and then are set to
 the parameters at step S16, and thereafter, the program flow returns to
 step S12 to repeat the above-mentioned processes.
 FIG. 8 is a flowchart showing a head position control process which is
 executed by the head position controlling module 33 shown in FIG. 5.
 Referring to FIG. 8, first of all in step S21, the position of the magnetic
 head 4 is controlled so that the head position is set to a predetermined
 initial position (a home position), and waiting is effected until a
 trigger signal is inputted in step S22. When the trigger signal is
 inputted (YES in step S22), the head position is moved by a predetermined
 movement distance in step S23. Then, it is decided in step S24 whether or
 not the next movement of the head is required. When there is required no
 movement of the head (NO in step S24), the head position control process
 is completed. When there is required another movement of the head (YES in
 step S24), the program flow returns to step S22 to repeat the
 above-mentioned processes. It is to be noted that a long time (which
 cannot be neglected as compared with the cycle of the Index signal) is
 required for the head position to reach the convergent position when the
 head is moved, and the head position does not normally converges within
 one Index signal.
 In the measuring apparatus 200 shown in FIG. 1, each of the modules 30 to
 33 having the various functions is programmed with one process with
 respect to one trigger signal, executing a series of processes without the
 intervention of the CPU. For example, the write controlling module 31
 executes writing data on each sector while changing the write current, and
 thereafter, the read controlling module 32 executes the measurement of
 data from each sector. The write controlling module 31 is preparatorily
 programmed with the write current to be set in the reference table memory
 52 with respect to each trigger signal, and the setting is changed for
 respective sectors originally by the write controlling module 31. Each of
 the write controlling module 31 and the read controlling module 32 is
 programmed with relationships (delay time and measurement time) between a
 received trigger signal and the time interval for which operations
 (writing and measurement) are to be executed and so on in the reference
 table memories 52 and 62 in addition to the above. By operating only for
 the required time (associated as a pair with the physical position of the
 hard disk 1), the measurement of the disk region in which the data has
 been written is certainly achieved.
 Therefore, according to the first preferred embodiment, the measuring
 process can be executed at a higher speed than that of the first prior
 art.
 In such a case where the spin stand 100 has a circuit for generating a
 plurality of trigger signals during one turn of the hard disk 1 and
 outputting the signals, the trigger signal may be used as a Sector signal
 without providing the frequency multiplier 42 shown in FIG. 2.
 An operation example of executing the writing or measurement with one track
 divided into a plurality of sectors will be described next.
 First Operation Exmaple
 First of all, as the first operation example, an example of a MR head bias
 current sweep will be described. Table 2 shows a processing procedure of
 the first operation example.
 TABLE 2
 Example of Sweep of head bias current
 Example of measurement with parameter values of MR head
 bias current changed for respective sectors in measurement
 (reading out)
 Enable
 Index 1: Erasing data on one track
 (in a special case where erasing means
 that the write pattern is "Erase" pattern)
 Index 2: Writing data on one track
 (for example, "HF (short-interval magnetization
 inverting data)" pattern)
 Index 3: Moving the head by the offset value
 Index 4: Waiting for convergence of movement
 of the head
 Index 5: Measuring the TAA with identical bias
 for respective sectors to measure reference values
 Index 6: Collecting all the TAA measurement data
 while changing MR head bias current
 for respective sectors, thereafter
 correcting the data, and
 displaying the result after correction
 As apparent from Table 2, all the operations are completed with six Index
 signals in the first operation example. For this execution, Table 3 shows
 a reference table stored in the reference table memory 41 of the trigger
 distribution module 30, while Table 4 shows reference tables stored in the
 reference table memories 52, 62 and 71 of the three controlling modules 31
 to 33.
 TABLE 3
 Reference Table of Trigger Distribution Module 30
 in Sweep Stage of MR Head Bias Current
 Index Signal 1 2 3 4 5 6
 OUT1 (Write Control) Index Index NOP NOP NOP NOP
 OUT2 (Read Control) NOP NOP NOP NOP Sector Sector
 OUT3 (Head Position) NOP NOP Index NOP NOP NOP
 TABLE 4
 Reference Tables of Controlling Modules 31, 32 and 33
 in Sweep Stage of MR Head Bias Current
 Trigger Signal No. 1 2 . . . 10 11 12 . . . 20
 Reference Table of
 Controlling
 Module 33
 Head Position (.mu.m) 0 -0.1
 Reference Table of
 Controlling
 Module 31
 Write Current (mA) 20 20
 Delay Time (msec) 0.1 0.1
 Operating Time 9.8 9.8
 (msec)
 Data Pattern Erase HF
 Reference Table of
 Controlling
 Module 32
 Bias Current (mA) 20 20 . . . 20 10 12 . . . 0.1
 Delay Time (msec) 0.1 0.1 . . . 0.1 0.1 0.1 . . . 0.1
 Operating Time 0.8 0.8 . . . 0.8 0.8 0.8 . . . 0.8
 (msec)
 Measurement item TAA TAA . . . TAA TAA TAA . . . TAA
 As is apparent from Table 3, the trigger signals OUT1, OUT2 and OUT3 to be
 outputted from the trigger distribution module 30 are listed with respect
 to the Index signal inputted to the trigger distribution module 30.
 Referring to Table 3, the Index signal is outputted directly as an Index
 trigger signal for the trigger signal OUT1 in response to an Index 1
 signal which serves as a first Index, the Index signal is outputted
 directly as an Index trigger signal for the trigger signal OUT1 in
 response to an Index 2 signal which serves as a second Index, and no
 signal is outputted subsequently. In this case, "NOP" means that no
 process is executed, i.e., no signal is outputted. In regard to the
 trigger signal OUT2, no signal is outputted until an Index 4 signal which
 serves as a fourth Index signal, and then, in response to an Index 5 which
 serves as a fifth Index signal, ten Sector signals outputted as the
 trigger signal OUT2 from the frequency multiplier 42 are continuously and
 sequentially outputted. Then, in response to an Index 6 which serves as a
 sixth Index signal, ten Sector signals outputted as the trigger signal
 OUT3 from the frequency multiplier 42 are continuously and sequentially
 outputted, and thereafter, the operation is completed. Further, in regard
 to the trigger signal OUT3, no signal is outputted until the Index 2
 signal which serves as the second Index signal, and then, in response to
 an Index 3 which serves as a third Index signal, the Index signal is
 outputted directly as the trigger signal OUT3, and no signal is outputted
 subsequently.
 Table 4 shows a list of the processing parameters which is executed in
 response to each trigger signal inputted to the controlling modules 31 to
 33. In the present preferred embodiment, a plurality of tracks 1t are
 formed in a concentric circular form arevolution the center O of the hard
 disk 1. As shown in FIG. 17, one revolution of the track of the hard disk
 1 (corresponding to the interval for the occurrence of the Index signal
 generated from the index sensor 5) is set to 10 milliseconds, and one
 track 1t is divided into ten sectors 1s (1 millisecond per sector). In the
 present first operation example, as is apparent from Table 2, after the
 writing process started by the Index 1 signal and the Index 2 signal of
 the trigger signal OUT1, the head position is moved by the Index 3 signal
 of the trigger signal OUT3, and thereafter, the reading process is
 executed. In this case, it is assumed that a time interval corresponding
 to two Index signals is required for the movement of the head position.
 That is, the trigger signal OUT2 is outputted after a lapse of a time
 interval corresponding to two Index signals subsequently to the Index 3
 signal which serves as the trigger signal OUT3 for moving the head.
 Only the head position, the data pattern, the write current or the bias
 current in the reading stage, delay time (meaning the time of delay from
 the trigger signal) and the operating time (meaning an operation
 continuing time from the start of the operation) are described as the
 parameters to be set for simplicity of explanation according to the
 description of the operation example. However, in practical, there exist
 the other variable parameters such as the write compensation amount, and
 therefore, the present invention is not limited to the above description.
 The present preferred embodiment adopts a system in which the controlling
 modules 31 to 33 do not discriminate whether the inputted trigger signal
 is the Index trigger signal or the Sector trigger signal except for the
 arrangement that the operating time is set relatively short in the
 operation based on the Sector trigger signal and the operating time is set
 relatively long in the operation based on the Index trigger signal. The
 present invention may be constructed so that all of the controlling
 modules 31 to 33 receive the Index trigger signal and divide the Index
 trigger signal into the Sector signals within the controlling modules
 31-33.
 Further, the first operation example will be described in detail below.
 (a) Initial setting: The initial value (left-hand end; trigger signal No.
 1) of the reference table of Table 4 is set, and after the setting, it is
 set to an "Enable" state. The term "Enable" means an operation to enable
 the Index from the spindle to be received.
 (b) Index 1: According to the reference table of Table 3, the Index trigger
 signal is outputted as the trigger signal OUT1. In response to this, the
 write controlling module 31 writes an erase pattern for 9.8 milliseconds
 after a delay of 0.1 millisecond from the Index trigger signal according
 to the reference table (trigger signal No. 1) of Table 4, and then, erases
 the data.
 (c) Index 2: According to the reference table of Table 3, the Index trigger
 signal is outputted as the trigger signal OUT1. In response to this, the
 write controlling module 31 writes an HF pattern for 9.8 milliseconds
 after a delay of 0.1 millisecond according to the reference table (trigger
 signal No. 2) of Table 4. After completing the writing process, the write
 controlling module 31 enters an end state.
 (d) Index 3: According to the reference table of Table 3, the Index trigger
 signal is outputted as the trigger signal OUT3. In response to this, the
 head position controlling module 33 sets the head position in a position
 shifted by -0.1 .m from the predetermined home position according to the
 reference table (trigger signal No. 2) of Table 4.
 (e) Index 4: According to the reference table of Table 3, the trigger
 signal is outputted to no output port of the trigger distribution module
 30. None of the controlling modules 31 to 33 operates. The reason why such
 a time is provided is that a considerable time is required for the
 convergence of the head position and therefore the next readable state
 cannot be achieved only with one Index signal.
 (f) Index 5: According to the reference table of Table 3, the Sector
 trigger signal is outputted as the trigger signal OUT2. In regard to this
 Sector trigger signal, ten trigger signals are outputted from the trigger
 distribution module 30 for one Index signal. The operation of the read
 controlling module 32 for respective sectors trigger signal will be
 described below.
 (f1) Sector 1: In response to the Sector trigger signal which serves as the
 trigger signal OUT2, the read controlling module 32 measures the TAA for
 0.8 millisecond after a delay of 0.1 millisecond according to the
 reference table of Table 4.
 (f2) Sector 2: In response to the Sector trigger signal which serves as the
 next trigger signal OUT2, the read controlling module 32 measures the TAA
 for 0.8 millisecond after a delay of 0.1 millisecond according to the
 reference table (trigger signal No. 11) of Table 4.
 (f3) Sector 3, 4, . . . , 9: The read controlling module 32 operates in a
 manner similar to that of the above (f1) and (f2).
 (f4) Sector 10: In response to the Sector trigger signal which serves as
 the last trigger signal OUT2, the read controlling module 32 measures the
 TAA for 0.8 millisecond after a delay of 0.1 millisecond according to the
 reference table (trigger signal No. 20) of Table 4.
 (g) Index 6: According to the reference table of Table 3, the Sector
 trigger signal which serves as the trigger signal OUT2 is outputted. In
 regard to this Sector trigger signal, ten Sector trigger signals are
 outputted from the trigger distribution module 30 for one Index signal.
 The operation of the read controlling module 32 for respective sectors
 trigger signal will be described below.
 (g1) Sector 1: In response to the Sector trigger signal which serves as the
 first trigger signal OUT2, the read controlling module 32 measures the TAA
 for 0.8 millisecond after a delay of 0.1 millisecond with an MR head bias
 current of 10 mA according to the reference table of Table 4.
 (g2) Sector 2: In response to the Sector trigger signal which serves as the
 second trigger signal OUT2, the read controlling module 32 measures the
 TAA for 0.8 millisecond after a delay of 0.1 millisecond with an MR head
 bias current of 12 mA according to the reference table of Table 4.
 (g3) Sector 3, 4, . . . , 9: Operations similar to those of the above (g1)
 and (g2) are executed except for the operation of changing (increasing)
 only the MR head bias current in a step of 2 mA.
 (g4) Sector 10: In response to the Sector signal which serves as the last
 trigger signal OUT2, the read controlling module 32 measures the TAA for
 0.8 millisecond after a delay of 0.1 millisecond with an MR head bias
 current of 28 mA according to the reference table of Table 4. After
 completing the measurement, the controller 60 of the read controlling
 module 32 completes its operation.
 FIG. 16 shows a timing chart in which the above-mentioned operations are
 arranged on the time axis, while Table 5 shows a timing chart of the
 operation for each Index signal. In contrast to the reference table of
 Table 4 which shows not the actual timing but the processing operation of
 the controlling module in response to the trigger signal, Table 5 shows
 the operation on the time axis for each Index signal.
 TABLE 5
 Operation Example of Each Control for Each Index Signal
 in Sweep Stage of MR Head Bias Current
 Index Signal 1 2 3 4 5 6
 Head Position Control
 Head Position (.mu.m) 0 -0.1
 Write Control
 Trigger Signal Index Index
 Write Current (mA) 20 20
 Delay Time (msec) 0.1 0.1
 Operating Time (msec) 9.8 9.8
 Data Pattern Erase HF
 Read Control
 Trigger Signal Sector Sector . . . Sector
 Sector Sector . . . Sector
 Bias Current (mA) 20 20 . . . 20
 10 12 . . . 0.1
 Delay Time (msec) 0.1 0.1 . . . 0.1
 0.1 0.1 . . . 0.1
 Operating Time (msec) 0.8 0.8 . . . 0.8
 0.8 0.8 . . . 0.8
 Measurement Item TAA TAA . . . TAA
 TM TAA . . . TAA
 In the first operation example, as shown in FIG. 17, a margin interval of
 0.1 millisecond is formed at the beginning and at the end of one sector
 1s. This margin interval is a time interval required for the setting and
 convergence of the set parameter value and also required as a margin for
 the variation in rotation of the spindle 2 and for the jitter of the Index
 signal.
 Second Operation Example
 As a further complicated example of a series of operations, an example in
 which a write operation is executed with the write current changed for
 respective sectors and the TAA is measured. Table 6 is a description of
 the operation. Table 7 shows a reference table of the trigger distribution
 module 30 for implementing the operation, while Table 8 shows a reference
 table of three controlling modules 31 to 33 for implementing the
 operation. Further, FIG. 18 is a timing chart showing an operation
 corresponding to the operation of the first operation example shown in
 FIG. 16, while Table 9 and Table 10 correspond to Table 5 of the first
 operation example and show the operation on the time axis for each Index
 signal. The manner of describing FIG. 18 and Tables of the second
 operation example is similar to those of the first operation example, and
 therefore, no description is provided for them.
 TABLE 6
 Example of Sweep of write current
 Example of measurement with the parameter value of write
 current changed for respective sectors in writing and with
 fixed parameter value in reading (measuring)
 Enable
 Index 1: Erasing one track
 Index 2: Writing data only on one track
 (For example, "HF (short-interval magnetization
 inverting data)" pattern)
 Index 3: Moving head by offset
 Index 4: Waiting for convergence of the movement of
 the head
 Index 5: Measuring the TAA for respective sectors for
 taking reference value
 Index 6: Setting back head offset
 Index 7: Waiting for movement convergence
 Index 8: Erasing preceding track
 Index 9: Writing data on one track while changing write
 current for respective sectors
 (write pattern is, for example, "HF (short-
 interval magnetization inverting data)"
 pattern)
 Index 10: Moving by head offset
 Index 11: Waiting for convergence of the movement of
 the head
 Index 12: Collecting all the TAA measurement data for
 respective sectors, thereafter correcting the
 data and displaying the result after correction
 TABLE 7
 Reference Table of Trigger Distribution Module 30 in Sweep Stage of Write
 Current
 Index Signal 1 2 3 4 5 6 7 8 9
 10 11 12
 OUT1 Index Index NOP NOP NOP NOP NOP Index
 Sector NOP NOP NOP
 (Write Control)
 OUT2 NOP NOP NOP NOP Sector NOP NOP NOP NOP
 NOP NOP Sector
 (Read Control)
 OUT3 NOP NOP Index NOP NOP Index NOP NOP NOP
 Index NOP NOP
 (Head Position)
 TABLE 8
 Reference Table of Controlling Modules 31, 32 and 33 in Sweep Stage of
 Write Current
 Trigger Signal No. 1 2 3 4 5 . . . 13 14 .
 . . 20
 Reference Table of
 Controlling Module 33
 Head Position (.mu.m) 0 -0.1 0 -0.1
 Reference Table of
 Controlling Module 31
 Write Current (mA) 20 20 20 10 12 . . . 28
 Delay Time (msec) 0.1 0.1 0.1 0.1 0.1 . . . 0.1
 Operating Time (msec) 9.8 9.8 9.8 0.8 0.8 . . . 0.8
 Data Pattern Erase HF Erase HF HF . . . HF
 Reference Table of
 Controlling Module 32
 Bias Current (mA) 20 20 20 20 20 . . . 20 20 .
 . . 20
 Delay Time (msec) 0.1 0.1 0.1 0.1 0.1 . . . 0.1 0.1 .
 . . 0.1
 Operating Time (msec) 0.8 0.8 0.8 0.8 0.8 . . . 0.8 0.8
 . . . 0.8
 Measurement Item TAA TAA TAA TAA TAA . . . TAA TAA .
 . . TAA
 TABLE 9
 Operation Example (Part 1) of Each Control for Each Index Signal in Sweep
 Stage of Write
 Current
 Index Signal 1 2 3 4 5 6
 7
 Head Position Control
 Head Position (.mu.m) 0 -0.1
 0
 Write Control
 Trigger Signal Index Index
 Write Current (mA) 20 20
 Delay Time (msec) 0.1 0.1
 Operating Time (msec) 9.8 9.8
 Data Pattern Erase HF
 Read Control
 Trigger Signal Sector Sector . . . Sector
 Bias current (mA) 20 20 . . . 20
 Delay Time (msec) 0.1 0.1 -- 0.1
 Operating Time (msec) 0.8 0.8 . . . 0.8
 Measurement Item TAA TAA . . . TAA
 TABLE 10
 Operation Example (Part 2) of Each Control for Each Index Signal in Sweep
 Stage of Write Current
 Index Signal 8 9 10 11 12
 Head Position Control
 Head Position (.mu.m) -0.1
 Write Control
 Trigger Signal Index Sector Sector . . . Sector
 Write Current (mA) 20 10 12 . . . 28
 Delay Time (msec) 0.1 0.1 0.1 . . . 0.1
 Operating Time (msec) 9.8 9.8 0.8 . . . 0.8
 Data Pattern Erase HF HF . . . HF
 Read Control
 Trigger Signal Sector
 Sector . . . Sector
 Bias Current (mA) 20
 20 . . . 20
 Delay Time (msec) 0.1
 0.1 . . . 0.1
 Operating Time (msec) 0.8
 0.8 . . . 0.8
 Measurement Item TAA
 TAA . . . TAA
 As a reference table describing method, a description on the time axis for
 each Index signal as shown in Table 5 is acceptable. In other words, it is
 acceptable in the present invention to write such instructions that the
 controlling module executes nothing ("NOP") in response to a certain
 trigger signal into the reference table of the controlling module and make
 the trigger distribution module 30 continue to transmit a trigger signal.
 In the construction of the above first preferred embodiment, the trigger
 distribution module 30, the write controlling module 31, the read
 controlling module 32 and head position controlling module 33 are
 separated by their functions and each of them is provided by one printed
 circuit board like in the form of a module. However, the present invention
 is not limited to this, and it is acceptable to constitute them one by one
 module or constitute the modules 30 to 33 by separate units.
 A modified preferred embodiment of the first preferred embodiment will be
 further described. The present modified preferred embodiment is
 constructed so that the controlling modules 31 to 33 have an ability of
 internally generating a Sector trigger signal or is constructed so that a
 Sector trigger signal and an Index trigger signal are consistently and
 externally inputted and they are switched over by a switch provided in the
 controlling module. With this arrangement, the construction of the trigger
 distribution module 30 can be simplified or eliminated.
 FIG. 9 is a block diagram showing a construction of the write controlling
 module 31a of the modified preferred embodiment in the latter case.
 Referring to FIG. 9, an Index signal is inputted to an input port I1 of a
 controller 50a and is inputted to an input port I2 of the controller 50a
 via the a-contact of a switch SW10. A Sector signal is inputted to the
 input port I2 of the controller 50a via the b-contact of the switch SW10.
 Tables 11 to 13 show reference tables A and B in the sweep stage of the MR
 head bias current of the modified preferred embodiment.
 TABLE 11
 Reference Table A of Head Position Controlling module
 (Modified preferred embodiment) in Sweep Stage of
 MR Head Bias Current
 Index Signal No. 1 2 3
 Trigger Signal Index NOP Index
 Reference Table B
 Head Position (. m) 0 -0.1
 TABLE 12
 Reference Table A of Write Controlling module 31a
 (Modified preferred embodiment) in Sweep Stage of
 MR Head Bias Current
 Index Signal No. 1 2
 Trigger Signal Index Index
 Reference Table B
 Write Current (mA) 20 20
 Delay Time (msec) 0.1 0.1
 Operating Time (msec) 9.8 9.8
 Data Pattern Erase HF
 TABLE 13
 Reference Table A of Read Controlling module (Modified preferred
 embodiment)
 in Sweep Stage of MR Head Bias Current
 Index Signal No 1 2 3 4 5 6
 Trigger Signal NOP NOP NOP NOP Sec Sec-
 tor tor
 Reference Table B (Part 1)
 Write Current (mA) 20 20 20 20 20 20 20 20
 20 20
 Delay Time (msec) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
 0.1 0.1
 Operating Time (msec) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8
 0.8 0.8
 Measurement Item TAA TAA TAA TAA TAA TAA TAA TAA
 TAA TAA
 Reference Table B (Part 2)
 Write Current (mA) 10 12 14 16 18 20 22 24
 26 28
 Delay Time (msec) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
 0.1 0.1
 Operating Time (msec) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8
 0.8 0.8
 Measurement Item TAA TAA TAA TAA TAA TAA TAA TAA
 TAA TAA
 In this case, the reference table A is a table which is referred in
 response to each Index signal inputted to the input port I1, and which
 shows a process executed in response to each Index signal. In this case,
 the switch SW10 is switched over to the a-contact when the trigger signal
 is "Index", and the switch SW10 is switched over to the b-contact when the
 trigger signal is "Sector". The reference table B shows operation
 parameter values to be set in response to the Index trigger signal or the
 Sector trigger signal inputted to the input port I2. This modified
 preferred embodiment has a unique effect that it is not required to be
 provided with the trigger distribution module 30.
 Further, another reference table describing method is shown in Table 14.
 TABLE 14
 Reference Table of Each Control (Modified preferred embodiment)
 in Sweep Stage of MR Head Bias Current (Mother Example)
 Trigger Signal No. 1 2 3 4 5
 Head Position Control
 Head Position (.mu.m) 0 NOP -0.1 NOP NOP
 Write Control
 Write Current (mA) 20 20 NOP NOP NOP
 Delay Time (msec) 0.1 0.1 NOP NOP NOP
 Operating Time (msec) 9.8 9.8 NOP NOP NOP
 Data Pattern Erase HF NOP NOP NOP
 Read control
 Bias Current (mA) NOP NOP NOP NOP 20
 Delay Time (msec) NOP NOP NOP NOP 0.1
 Operating Time (msec) NOP NOP NOP NOP 0.8
 Measurement Item NOP NOP NOP NOP TAA
 According to the other describing method, the processes which is executed
 every inputted Index signal by the controlling modules 31 to 33 on the
 time axis are described in a reference table. The example of Table 14 is
 an example in which the read controlling module 32 executes the TAA
 measurement one time, and this example cannot execute the write and
 reading processes for respective sectors.
 Second Preferred Embodiment
 The second preferred embodiment is provided for solving the problems of the
 second prior art and is able to execute at a high speed a measurement
 requiring statistical processing of a number of measurement data such as
 the evaluation of an instability by measuring a plurality of times an
 identical measurement while the hard disk 1 makes one turn. That is, a
 series of works of writing (writing and abandoning) and reading is
 executed while the hard disk 1 is rotated by one turn as shown in FIG. 13
 in the second prior art, whereas a series of works of writing (writing and
 abandoning) and reading is completed within one sector 1s as shown in FIG.
 19 in the second preferred embodiment. With this arrangement, a plurality
 of times of measurements can be achieved in the time interval for which
 the hard disk 1 is rotated by one turn, thereby allowing a high-speed
 measurement to be achieved. In this case, the data to be read out has been
 preparatorily written on the track 1t of the hard disk 1. The data written
 in the writing (writing and abandoning) operation is not provided for the
 purpose of reading out but for the purpose of promoting the change in
 characteristics of the read element of the magnetic head 4 due to the
 write operation. The second preferred embodiment can be implemented by
 merely rewriting the reference table by means of the instrument
 construction of the first preferred embodiment or its modified preferred
 embodiment.
 Also in this measurement, in an attempt at compensating for the
 non-uniformity in the disk characteristics of sectors in calculating the
 variation through the statistical processing, by previously and
 individually calculating the statistic value of each sector and handling
 only the variation between the sectors, it is allowed to compensate for
 the non-uniformity. In such a case where the average values of the sectors
 themselves are changed as shown in FIG. 20, when viewing the variation by
 mixing the data of all the sectors, even the non-uniformity of the disk is
 calculated as a variation. If they are processed individually for
 respective sectors, a variance . for one revolution can be calculated by
 the following equation:
EQU ..sup.2 =..sub.1.sup.2 +..sub.2.sup.2 +..sub.3.sup.2 + . . . +..sub.N.sup.2
 (1)
 where ..sub.n is the variance of the data distribution of the sector n
 (n=1, 2, . . . , N, and N is the number of sectors on one revolution of
 the track). By calculating the variance . for one revolution by means of
 the above equation (1), the stability and the variation of the read signal
 through the writing process can be measured, and there is such a unique
 advantageous effect that the evaluation of the variation of the data is
 not influenced by the average value of respective sectors.
 Therefore, according to the measuring apparatus of the second preferred
 embodiment, the measurement can be executed at a higher speed and more
 correctly than that of the prior art.
 Third Preferred Embodiment
 The third preferred embodiment of the present invention is provided for
 solving the problems of the third prior art and is characterized in that
 the measurement is executed by continuously sweeping the parameter value
 when the hard disk 1 is rotated for one turn. Concretely Speaking, after
 writing a write signal while continuously changing the write parameter for
 one track, the write signal is read out as a read signal with the read
 parameter fixed for the track. Otherwise, after writing a write signal
 with a fixed write parameter for one track, the write signal is read out
 as a read signal while continuously changing the read parameter with
 respect to the track.
 That is, according to the measurement of the third prior art described with
 reference to FIG. 21, the time interval for moving the head position takes
 a long time as compared with that for the rotation of the spindle, and
 therefore, the measuring method of the first preferred embodiment and the
 second preferred embodiment for measuring the data for one revolution
 through division into the sectors cannot be used. In the third preferred
 embodiment, a measurement of, for example, the track profile measurement,
 which has conventionally taken a very long time, can be executed in a
 shorter time by continuously sweeping the parameter value when the hard
 disk 1 is rotated by one turn.
 For example, as shown in FIG. 22, by moving the magnetic head 4 so that the
 head crosses inclined to the center line 80c of a track 80 on which data
 has been written, the dependency of the head position and the read
 amplitude can be measured in a time interval for which the hard disk 1 is
 rotated by one turn. It is also acceptable to use a method of executing
 the writing while moving the magnetic head 4 in the writing stage and not
 moving the magnetic head 4 in the reading stage.
 In the third preferred embodiment, in an attempt at compensating for the
 non-uniformity of the characteristics of the hard disk 1 in a manner
 similar to that of the above-mentioned case, a more correct measured value
 is obtained by using a measured TAA obtained by not moving the magnetic
 head 4 as a reference value Tar as shown in FIG. 23A, collating or
 checking a measured value Tam measured by moving the magnetic head 4 with
 the above reference value Tar and correcting the same as shown in FIG.
 23B.
 Referring to FIGS. 23A, 23B and 23C, the axis of abscissas represents the
 position in one revolution of the track of the hard disk 1 (referred to as
 a "disk position" hereinafter) and is expressed as a "head position" by
 making the head position with respect to the center lien 80c of the track
 correspond to the above-mentioned disk position. In the example shown in
 FIGS. 23A, 23B and 23C, a calculated value obtained by dividing the
 measured value Tam by the reference value Tar is used as a compensated
 measured value Tac. Although the division calculation is used for the
 correction in the third preferred embodiment, the present invention is not
 limited to this, and another corrective calculation formula may be used.
 In the third preferred embodiment, in regard to the sweep of the parameter
 sweep, a continuous sweep is achieved by continuing to change the set
 value of the parameter in a sufficiently short time as compared with the
 parameter convergence time. The continuous sweep of the head position and
 the frequency is executed by this method.
 FIG. 25 shows a further modified preferred embodiment of the parameter
 value sweeping method. For example, when sweeping a parameter of which the
 convergence time of the setting value is slower than the rotating cycle of
 the spindle 2, there is provided a construction in which a parameter value
 on the upstream side of the desired initial value is used as an initial
 value, and then, the sweep is started prior to the start of the
 measurement, so that a stabilized measurement is achieved during the
 measurement. With this arrangement, a more correct measurement can be
 achieved.
 Fourth Preferred Embodiment
 The fourth preferred embodiment of the present invention is characterized
 in that a plurality of mutually different measurement items are measured
 during the time interval for which the hard disk 1 is rotated by one turn.
 In this case, concretely speaking, by writing different write data in
 different sectors, a plurality of different measurements are executed
 during the one revolution. For example, as shown in FIG. 24, an LF
 (long-interval magnetization inverting data) is written into a Sector 1,
 an HF (short-interval magnetization inverting data) is written into a
 Sector 2, and then, a pseudo random signal is written into a Sector 3.
 Then, the TAA of the LF (long-interval magnetization inverting data) is
 measured in the Sector 1, the TAA of the HF (short-interval magnetization
 inverting data) is measured in the Sector 2, and then, a non-linear bit
 shift amount (NLTS) is measured in the Sector 3. That is, after writing a
 write signal with the write parameter of an item changed for respective
 sectors, the written write signal is read out by a predetermined read
 parameter for respective sectors, the read write signal is measured as a
 read signal and a measurement result of the measurement item changed for
 respective sectors is obtained based on the measured read signal.
 The fourth preferred embodiment can be implemented by merely rewriting the
 reference table with the instrument construction of the first preferred
 embodiment or its modified preferred embodiment. Therefore, with the
 construction of the fourth preferred embodiment, the measurement of the
 performance of the hard disk 1 can be executed at a higher speed than that
 of the prior art.
 Modified Preferred Embodiment
 The above-mentioned preferred embodiments each describe the measuring
 apparatus for the recording unit including the recording medium of the
 hard disk. However, the present invention is not limited to this, and it
 can be applied to a measuring apparatus for use in a recording unit for
 measuring performance characteristics of a recording unit including a
 recording medium of a floppy disk, an optical disk such as CD, DVD, a
 magneto-optical disk (of ROM, write once type, rewriting type) or the like
 and components such as a head for recording a data signal on the above
 recording medium.
 According to the preferred embodiments of the present invention, the
 performance characteristics of the recording medium can be measured at a
 higher speed than that of the prior art.
 Further, when the correctively calculating means is further provided, the
 measured value can be properly corrected and more correct measured value
 can be obtained.
 Further, when the statistically calculating means is further provided,
 statistically processing the measured value can be properly performed and
 more correct measured value can be obtained. Furthermore, there can be
 obtained calculation results of the statistical processing in which the
 evaluation of the variation in the calculation results thereof is
 influenced by the average value for respective sectors.
 Although the present invention has been fully described in connection with
 the preferred embodiments thereof with reference to the accompanying
 drawings, it is to be noted that various changes and modifications are
 apparent to those skilled in the art. Such changes and modifications are
 to be understood as included within the scope of the present invention as
 defined by the appended claims unless they depart therefrom.