SU678515A1 - Method of measuring the width of effective working gap of magnetic head - Google Patents

Description

To improve measurement accuracy, it is necessary to record and play back a control signal with a constant wavelength to simultaneously measure the frequency of the control and measurement signals, and judge the width of the effective working gap of the magnetic rarjoBKH by measuring the ratio of the specified frequencies and the wavelength of the control signal .

The drawing shows a block diagram of an apparatus for implementing the inventive method, one of the embodiments.

Olio contains a tape mechanism 1, magnetic tape 2, the first recording mag-. nitric head 3, test reproducing magnetic head 4, second recording magnetic head 5, second reproducing magnetic head 6, first recording amplifier 7, first reproducing amplifier S, second recording amplifier 9, second reproducing amplifier 10, measuring signal generator 11 frequency, oscilloscope 12, first pulse extraction circuit 13, and frequency counter 14.

Consistently with the input of the movement of the magnetic tape 2, a first clamping head 3 is installed, the input of which through the first amplifier 7 is connected to the output. generator 11, test magnetic head 4, the output of which through the first amplifier 8 is connected to the input of the oscilloscope 12, the second recording magnetic head 5 and the second reproducing magnetic head 6, the output of which through a serially connected second amplifier 10, circuit 13, second amplifier 9 connect to the input of the second recording head 5.

The output of the circuit 13 and the output of the generator 11 are connected to the input of the frequency of the 14.

Using the first recording magnetic head 3, the first amplifier 7 and the generator 11, a magnetic recording of the measurement signal is applied to the track of the magnetic tape 2. When moving the magnetic tape 2 past the test reproduction, the 1 head 4 in its winding is induced by EMF, which is amplified by the first amplifier 8 and recorded by an oscilloscope 12. The generator frequency 11 is changed until the EMF induced in the winding of the magnetic head 4 does not take the minimum value and the wavelength of the recorded measurement oscillations, and therefore the width of the effective working gap of the magnetic head 4, is determined by formula (1). It can be seen from formula (1) that the instability of the speed of magnetic tape 2 leads to an error in measuring the width of the effective working gap of magnetic

heads. To eliminate this error, the second track of magnetic tape 2 is recorded with a control signal with a constant predetermined wavelength X. The frequency k} | tolyu1o signal f is associated with the speed of movement of the magnetic tape

Simultaneously with recording the frequency of the measuring signal, the frequency of the reference signal and the width of the effective working gap of the test head are measured by the formula

(3)

t-- L

f

The pilot signal is recorded in the following way. Using the second recording magnetic head 5 and the amplifier 9, a magnetic mark is recorded on the second track of the magnetic tape 2. When the magnetic tape 2 is moving, this mark is reproduced by the second reproducing magnetic head 6 installed at a distance X from the second magnetic recording head 5. The reproduced mark is amplified by the second amplifier 10 and through the extraction circuit 13 of the first pulse and the amplifier 9 is fed to the input of the second recording magnetic head 5. There is a rewrite of the magnetic tag. The frequency of recording the control signal is determined by the formula (2).

Thus, with a minimum of EMF at the output of the subject; of the reproducing magnetic head 4, which is fixed by the oscilloscope 12, measures the ratio of the frequencies of the control signal and the measuring signal, which are supplied respectively from the output of the circuit 13 and the output of the generator 11 to the inputs of the frequency meter 14, operating in the frequency ratio control mode and 4 is determined by the formula (3),

The proposed method eliminates the error caused by the instability of the speed of movement of the magnetic tape, and, consequently, improves the measurement accuracy.

Claims (3)

1.Parkhomenko V.I. Magnetic heads. M., - L., Gosenergoizdat, 1960, p.57-60. 2.Efimov EG. Magnetic heads. M., Energie, 1967, pp.49-51. 3. Authors certificate of the USSR N 358968, cl. G 11 B 5/46, 1974. d rt