JPH0223950B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape remaining amount time measuring device.

Some conventional magnetic tape reproducing/recording apparatuses detect the rotational speed of a tape supply shaft, perform the following calculations using a so-called microcomputer, and display the remaining amount of time on the tape.

Normally, the tape is fed at a constant speed, so the remaining tape time T depends on the rotation period t of the supply shaft. T=υ ² /4π・△γ・(t・α) ² −γ ₁ ²・π/△γ
・υ…(1) It is expressed by the formula.

However, υ is the tape feeding speed, Δγ is the tape origin, γ ₁ is the tape reel hub diameter, and α is the number of detection poles.

Conventionally, a microcomputer was configured with a program to calculate the rotation period and a program to calculate the above equation (1) from this calculation result to display the remaining amount of time, so the calculation process was time consuming and expensive. It had some drawbacks. Moreover, the remaining amount display time unit is rough, more than 1 minute, and the numerical counter,
It has been difficult to simultaneously implement other functions such as a cue counter.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a tape remaining amount measuring device which has an extremely simple and inexpensive configuration, allows the remaining amount time unit to be set to a very small value, and is capable of high-speed processing, thereby eliminating the drawbacks of the prior art.

An embodiment of the present invention will be described below based on the drawings. In FIG. 1, 1 is a crystal oscillator and 2 is a frequency divider. Reference numeral 3 denotes a detection device for detecting the rotation of a reel shaft (not shown) on the tape supply side, which generates, for example, one detection pulse for each rotation. 4
is a timing pulse generation circuit, and its output terminal a
From ~e, pulses shown in FIG. 2() to () are generated every time the detection pulse shown in FIG. 2() arrives. 5 is a pulse generating circuit, and the clock pulses shown in FIG. 2() and () are generated from its output terminals f and g.
The width of the pulses in FIGS. 2(), (), () and the period of the clock pulses in FIGS. 2(), () will be described in detail later. 6 is a selection circuit, 7 is a remaining time counting circuit, 8 is a latch circuit, 9 is a decoder, 1
0 is a display device.

In the above configuration, first, the pulse widths and the periods of the clock pulses will be explained. As mentioned above, the remaining time T of the tape is expressed by equation (1) using the rotation period t of the reel shaft as a parameter, and this is expressed by the quadratic curve _l0 in FIG. In the same figure, the rotation period t ₀ is the minimum rotation period of the supply reel,
In other words, it shows the cycle when the remaining amount of tape is 0 and the reel is rotating in an empty state. Also, the rotation period t ₂
indicates the maximum period of the supply reel, that is, the rotation period when the tape is wound to the maximum extent.

In this example, the quadratic curve l ₀ is approximated by two straight lines l ₁ and l ₂ with the rotation period t ₀ as the boundary, and the remaining time is calculated by counting the clock pulses of the frequency corresponding to the slope of each straight line. It is used to measure.

Specifically, the width of the pulse shown in FIG. 2() is set to time _t0 , and counting by the counting circuit 7 is prohibited while this pulse is being generated. Then, the width of the pulse shown in Fig. 2 () is set to (time t ₁ - _{t 0} ), and the frequency of the clock pulse shown in Fig. 2 () is made to correspond to the slope of the straight line l ₁ to obtain T ₁ /(t ₁ - t 0 ). ₀ )
(T ₁ : remaining amount time at rotation period t ₁ ),
This clock pulse is counted during the above time (t ₁ -t ₀ ). Further, by setting the width of the pulse in Figure 2 () to time (t ₃ - t ₁ ) and making the frequency of the clock pulse in Figure 2 () correspond to the slope of the straight line l ₂ , we obtain (T ₂ - T ₁ )/ (t ₂ − _{t 1} ) (T ₂ : remaining amount time at rotation period t ₂ ), and the above time (t ₂ − t ₁ )
This clock pulse is counted during this period.

By performing the above-mentioned counting operation until the next detection pulse arrives, the content of the count is directly displayed as the remaining amount of time.

Next, the operation will be explained in detail. When a detection pulse is generated from the detection device 3, a pulse as shown in FIG. 2() is generated from terminal a of the timing pulse generation circuit 4.
The gate of the selection circuit 6 is closed and no clock pulses pass through. On the other hand, the pulse shown in FIG. 2() is generated from the terminal d, and the counting circuit 7 is reset. Next, when the pulse shown in FIG. 2() is generated from the terminal b, the clock pulse shown in FIG. 2() from the terminal f of the pulse generating circuit 5 is selected and passed, and
is counted. When the pulse shown in FIG. 2() is generated from the terminal c, the clock pulse shown in FIG. 2() from the terminal g is selected and passed, and is counted by the counting circuit 7.

For example, as shown by the broken line in Figure 2, if the next detection pulse is generated after time t ₃ from the generation of the above detection pulse, this detection pulse will stop the pulse from terminal b and stop counting. . At the same time, the pulse shown in FIG. 2() is generated from the terminal e, and the count contents of the counting circuit 7 are latched in the latch circuit 8 and displayed. The content of the count at this time is the remaining amount time T ₃ at the rotation period t ₃ and can be displayed as is without any calculation or conversion.

In the above embodiment, the quadratic curve l ₀ is approximated by two straight lines, but by approximating it by a larger number of straight lines, the unit time can be set smaller.

Further, the remaining amount time can be similarly measured not only by detecting the rotation period of the reel shaft on the supply side but also by detecting the rotation period of the reel shaft on the winding side. However, in this case, the characteristic curve of the remaining amount time is represented by the quadratic curve _l3 in FIG.

As described above, according to the present invention, it is only necessary to count clock pulses, and there is no need for processing such as calculation or conversion, so the configuration can be extremely simplified.
Moreover, high-speed processing is possible. Further, by performing the linear approximation finely, there is an advantage that the remaining amount time unit can be set to an extremely small time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a time chart for explaining the operation,
FIG. 3 is a characteristic curve diagram showing the remaining amount of tape using the reel shaft rotation period as a parameter. 3...Detection device, 5...Pulse generation circuit, 6...
...Selection circuit, 7...Counting circuit.

Claims (1)

[Scope of Claims] 1. A pulse generation circuit that generates clock pulses with frequencies corresponding to the slopes of a plurality of straight lines that approximate a characteristic curve of remaining tape time expressed using the rotation period of the reel shaft as a parameter; a detection device that detects the rotation of the detection pulse and generates a detection pulse; a selection circuit that sequentially selects each of the clock pulses after a time corresponding to the minimum rotation period of the reel shaft has elapsed from the arrival of the detection pulse; A tape remaining amount time measuring device comprising a counting circuit that counts the clock pulses selected by the selection circuit until the next detection pulse arrives.