SU572705A1 - Magnetic carrier speed variation measuring device - Google Patents

Description

I

The invention relates to the field of instrumentation, in particular, to equipment intended for measuring the speed of movement of a magnetic carrier and the deviations of this speed from its nominal value.

A device for measuring the lateral movement of a moving magnetic tape 1 is known. A residual of this device is a large measurement error when the reading element moves from the end of the track to its beginning.

And the closest to the invention. According to the technical essence, there is a measuring device of fluctuations in the speed of movement of a magnetic recording medium, consisting of a series-connected phase detector, a threshold device of an electronic switch, a driver, a demodulator, an amplifier, and a measuring device 2. The device also contains a split load stage which is connected to the input of the phase meter, which is the input of the device, and the outputs are connected to the signal inputs of the switch, which allows to reduce the effect of the jump phase zy of the reproduced signal at transition of the reading element from the end of a track to its beginning.

However, this device does not provide the necessary measurement accuracy.

To improve the measurement accuracy, a phase shifter is inserted into the device, which is connected between the input terminal and the signal inputs of the electronic switch,

and the delay LINE is connected between the inputs of the phase detector, the threshold device is designed as a multi-threshold, and the electronic switch is an electronic switch.

FIG. I Shows the dependence of measurement error | b | from the phase jump f ° in the case of using conventional measuring means (solid line) and in the case of using a known device (dotted

line); in fig. 2 - the same, in case of using the proposed device; in fig. 3 is a block diagram of the described device.

The delay line 1 is turned on by the entrance of the phase detector 2, which is connected via a multi-threshold device 3 to the control input of the electronic switch 4. The signal inputs of the latter are connected to the outputs of the phase shifter 5, whose input

connected to the input terminal of the meter 6. The output of the electronic switch 4 through the driver 7, the demodulator 8, the amplifier 9 is connected to the measuring device 10. The DEVICE operates as follows.

The signal from the magnetic recording apparatus under investigation (AMZ) is simultaneously fed to the input of phase detector 2 and phase shifter 5. The phase shifter has taps, and the phase shift of signals at adjacent taps is 3607t, where t is the number of taps. At the moment of transition of the reading element from the end to the beginning of the track, a phase jump of the reproduced signal occurs. The value of the phase jump is in the range of 0-360 °. In this case, the phase jump is detected by the phase detector 2 using the delay line 1. The signal amplitude at the output of the phase detector unambiguously characterizes the phase jump. The duration of the burst depends on the delay time of the signal by the delay line and is always constant. The multi-threshold device 3 switches at the moment of a phase jump and the signal at its output corresponds to the amplitude of the output signal of the phase detector 2. The output level of the multi-threshold device 3 controls the operation of the electronic switch 4.

In addition to the aforementioned circuit, the input signal is fed to the input of a phase shifter 5 having taps. At the time of a phase jump, an electronic switch 4, controlled by a series circuit from phase detector 2 and multithreshold device 3, connects that phase tap to the input of shaper 7, the phase shift of the signal corresponding to the phase jump and opposite in sign.

The number of output levels of the multithreshold device 3 is selected from the conditions of the smallest measurement error due to the phase jump of the input signal, the largest

possible values of measured speed fluctuations. When the measurement error is reduced by half. By increasing the number of t, one can achieve a negligence.

Shaper 7 produces a signal shaping in order to eliminate the influence of spurious amplitude modulation. At the output of the demodulator 8, a signal appears that is proportional to the velocity fluctuations. This signal is amplified by amplifier 9 and measured by instrument 10.

Claims (2)

1. USSR author's certificate No. 291243, cl. G IW 27/10, 1969. 2. USSR author's certificate No. 444110, cl. G 01 P 3/22, G IV, 5/00, 1972. oh to theo 21 o 360 . / fug. 2