JPH0223951B2 - - Google Patents

Description

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

Some conventional magnetic tape playback/recording devices detect the rotational speed of a tape winding shaft, perform the following calculations using a so-called microcomputer, and display the running time of the tape.

Normally, the tape is fed at a constant speed, so the tape running time T depends on the rotation period t of the take-up shaft.T=v ² /4π・△r・(t・α) ² −r ₁ ²・π/△ r・
v...(1) It is expressed by the following formula.

However, v: tape feeding speed, Δr: tape thickness, r ₁ : tape reel hub diameter, α: 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 running time, which was not only time-consuming but also expensive. It had some drawbacks. Moreover, the display time unit is roughly one minute or more, and it is difficult to simultaneously implement other functions such as a numerical counter and cue counter.

Therefore, the present invention has an extremely simple and inexpensive configuration.
Furthermore, the present invention provides a tape running time measuring device that allows the running time unit to be set very small and can perform high-speed processing, thereby eliminating the drawbacks of the conventional tape running time.

Hereinafter, one embodiment of the present invention will be described 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 winding side, which generates, for example, one detection pulse for each rotation. 4 is a timing pulse generation circuit whose output terminals 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 running time counting circuit, 8 is a latch circuit, 9 is a decoder, 1
0 is a display device.

In the above configuration, the width of each pulse and the period of the clock pulse will be explained first. As mentioned above, the running time T of the tape is expressed by equation (1) using the rotation period t of the take-up reel shaft as a parameter, and this is expressed by the quadratic curve l ₀ in FIG. In the figure, the rotation period t ₀ indicates the minimum rotation period of the take-up reel, that is, the period when the tape travel distance is 0 and the reel is rotating in an empty state. Further, the rotation period t ₂ indicates the maximum period of the take-up 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 ₁ as the boundary, and the clock pulses of the frequency corresponding to the slope of each straight line are counted. It measures time.

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 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. t0} )
(T ₁ ; running time when rotation period t ₁ ),
This clock pulse is counted during the above time (t ₁ -t ₀ ). Furthermore, while setting the pulse width in Figure 2 () to time (t ₃ - t ₁ ),
(T ₂ - T ₁ )/(t _{2 -} t ₁ ) (T ₂ ; Rotation period t ₂
), and set the above time (t ₂ −
This clock pulse is counted during t ₁ ).

By performing the above-mentioned counting operation until the next detection pulse arrives, the contents of the count are directly displayed as the running 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. 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 the counting circuit 7 is counted. Then, when the pulse shown in Fig. 2 () is generated from terminal c,
The clock pulses of FIG. 2() from terminal g are selected and passed through and counted by counting circuit 7.

For example, as shown by the broken line in FIG. 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 the counting will start. stop.
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 travel time T ₃ in 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 traveling time can be similarly measured not only by detecting the rotation period of the reel shaft on the take-up side but also by detecting the rotation period of the reel shaft on the supply side. However, in this case, the characteristic curve of the running time is represented by a quadratic curve _l3 in FIG.

Further, in the above embodiment, the measurement of the running time was described, but the remaining time of the tape can be measured in the same manner. Muaya, remaining time
T′ depends on the rotation period t′ of the supply shaft. T′=v ² /4π・△r・(t′・α) ² −r ₁ ²・π/△r
・v It is expressed by the formula.

Therefore, in the above embodiment, the remaining amount time can be obtained from the rotation period of the supply shaft in exactly the same way as the running time was obtained from the rotation period of the take-up shaft.

As described above, according to the present invention, the running time of the tape can be measured simply by counting clock pulses.
Since processing such as calculation and conversion is not required, the configuration can be extremely simplified and high-speed processing is possible. Another advantage is that by performing fine linear approximation, the measurement time unit can be set to an extremely small time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart for explaining the operation,
FIG. 3 is a characteristic curve diagram showing the tape running time 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 gradients of a plurality of straight lines that approximate a characteristic curve of tape running time expressed using the rotation period of the reel shaft as a parameter; a detection device that detects rotation 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 running time measuring device comprising a counting circuit that counts the clock pulses selected by the selection circuit until the next detection pulse arrives.