SU1631595A2 - Device for marginal checking of resonant frequency of crystal transducer of autotracking magnetic head - Google Patents

Abstract

The invention relates to instrumentation, in particular, to devices for measuring the parameters of the auto-tracking heads of video recorders for oblique-line recording, and makes it possible to increase the reliability of the device by eliminating the possibility of an unlimited increase in the amplitude of the ozonance oscillations of the piezotransducer. The pulses from the inverted outputs of the first and the second one-shot 8 and 9 are fed to the inputs of element 2I-NOT, the output of which is connected to the logical input of the analog switch 16. The switch is in the closed state during the action of the pulses of the one-shot 8 and 9. At the end of the action of these pulses the analog the switch 16 opens and the phase-shifted signal from the output of the first low-pass filter 7 is fed to the second input of the high-voltage amplifier 2 and suppresses its oscillations, 2 sludge. with s

Description

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The invention relates to instrument making, namely to devices for measuring the parameters of auto-tracking heads of video recorders for oblique-line recording.

The purpose of the invention is to increase the reliability of the device by eliminating the possibility of an unlimited increase in the amplitude of the resonant oscillations of the piezo transducer.

FIG. 1 shows a functional diagram of the proposed device; in fig. 2 - time diagrams that show his work.

A device for tolerance monitoring of the resonant frequency of a piezoelectric transducer of an auto-tracking magnetic head contains a series-connected pulse voltage generator 1, a high-voltage amplifier 2 loaded on a piezo-converter 3 with a magnetic head 4 and a piezoelectric sensor 5 attached to it, and the output of which are connected in series by amplifier 6 and first filter 7 low pass. The device also contains the first and second one-shot 8 and 9, the first and second Comparators 10 and 11, the second low-pass filter 12, the element And 13 and the block 14 of the display. One of the inputs of the element And 13 is connected to the output of the generator 1 by successively connected first and second one-shot 8 and 9, the other input of the element And 13 to the output of the first low-pass filter 7 through the first comparator 10. The output of the element And 13 through sequentially the second low-pass filter 12 and the second comparator 11 are connected to the start of the display unit 14, the logic element 2I-HE 15, the switch 16 of the lot signals and the phase-shifting circuit 17 are added to the device, the first input of the element 2I-HE 15 is connected to the inverter The output of the first one-shot 8, the second input to the inverting output of the second one-shot 9, and the output to the logical input of the switch 16 analog signals, the analog input of which is connected to the output of the first low-pass filter 7 through the phase shift circuit 17. The output of the switch 16 analog signals connected to the second input of the high-voltage amplifier 2.

The device works as follows.

From the output of the generator 1 to the piezoelectric transducer 3, the voltage pulses Ur amplified by a high voltage amplifier 2 are amplified {Fig. 2, a) with a period of following T (t-current time) The amplified pulses Ur excite a piezoelectric transducer 3 and

put it into oscillation mode with its own resonant frequency. At the same time, a signal proportional to the instantaneous swing of these oscillations appears at the output of the piezoelectric sensor 5, which through the amplifier 6 and the first low-pass filter 7 is fed to the input of the first comparator 10, as well as through the phase-shifting circuit 17 to the analog input of the switch 16 analog signals. The waveform if1 (fig. 2, c) at the output of the first low-pass filter 7 reflects the nature of the resonant vibrations of the piezoelectric transducer 3, whose range decreases exponentially within the interval T. The first comparator 10, which has a zero threshold voltage, This signal generates a pulsed signal UK (Fig. 2, d), the pulse duration of which is equal to half the period of resonant oscillations of the piezoelectric transducer 3, This signal arrives at one of the inputs of the element And 13. Simultaneously, the pulses the output of the generator 1 starts the first one-shot 8, which generates UOBI pulses at the direct output (shown by dashes n FIG. 2, d). Using the cut of these pulses, the second one-shot 9 is started, forming at its direct output the pulses Uos2 (shown by a solid line on Fig. 2, e), which arrive at the other input of the element And 13. The duration and temporary arrangement of the pulses 1) o2 are chosen such that they start earlier and end after one of the first UK pulses formed by the first comparator 10. As a result at the output of the element And 13 are of pulses Up (FIG. 2, е), the duration of which Tp is 1 / 2fp (where fp is the resonant frequency of the piezoelectric transducer of the auto-tracking head). From the sequence of pulses Up using the second low-pass filter 12, the constant component Un (Fig. 2, e) is extracted, which is fed to the input of the second comparator 11. The voltage Un uniquely determines the value of the resonant frequency fp of the piezoelectric transducer of the auto-tracking head.

Since the passport value of the frequency fp has a spread of Af, the voltage Un also has a corresponding allowable variation of ± A Un (Fig 2, e). The second comparator is 11b, brane of the window detector type and has threshold voltages equal to (Un + + A Un) and (Un - A Up), which provides the required accuracy of measurements.

If the resonant frequency of the piezoelectric transducer of the auto-tracking head exceeds the allowable one, the second comparator 11 is activated and a voltage appears at its output, signaling that the auto-tracking head does not match the passport parameters. The indicated voltage can be registered by the display unit 14.

Pulses 00v1 (Fig. 2, g) are applied to one of the inputs of element 2I-NOT 15, and pulses 00v2 (Fig. 2, h) are supplied to the other. From the output of element 2I-NOT, the signal and (Fig. 2, i) is fed to the logic input of the analog switch 16 and holds it in the closed state.

The analog input of the switch 16 is fed through the photo-shifting circuit 17, the phase-shifted signal 11ф1 from the output of the first filter 7 of the lower charts. At the end of the pulses Uj- (Fig. 2, I), the analog switch 16 opens and a UKOM signal appears on its output (Fig. 2, k), which is fed to the second input of the high-voltage amplifier 2. The amplified signal acts on the piezoelectric transducer 3 and suppresses its oscillations after several periods (shown by dashes in Fig. 2, c).

Claims (1)

The invention The device for the tolerance control of the resonant frequency of the piezoelectric transducer of the auto-tracking magnetic head St. N; 1529283, characterized in that, in order to increase the reliability of the device by eliminating the possibility of an unlimited increase in the amplitude of resonant oscillations of the piezoelectric transducers, element 2I-NOT, the analog signal switch and the phase-shifting circuit are additionally introduced, the first and second one-vibrators are equipped with additional inverse outputs and the high-voltage amplifier has an additional input, the first input of element 2И- is NOT connected to the inverse output of the first one-shot. the second input of element 2И-NOT is connected to the inverting output of the second one-vibrator, the output of element 2И-NOT is connected to the logical input of the analog signal switch, the analog input of which is connected to the output of the first low-pass filter through the phase shifter, and the switch output of the analog signals is connected to an additional high-voltage input booster. FIG. 2