JPH0714912Y2 - Level display device - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application This invention relates to a level display of a digital recording / reproducing apparatus,
Particularly, the present invention relates to a level display device suitable for displaying an output offset level of an A / D converter.

(B) Prior Art In a digital recording / reproducing apparatus having a level indicator for displaying an output level, a block diagram as shown in FIG. 4 is provided when adjusting an output offset voltage of an A / D converter. It was In the figure, 1 is an analog signal input terminal, 2 is an A / D converter that converts the analog signal supplied to the input terminal 1 into a digital signal, and 4 is an offset for adjusting the output offset voltage of the A / D converter 2. The adjuster 5 modulates the output digital signal of the A / D converter 2 into a predetermined exchange pattern, performs signal processing into a signal that can be recorded on a recording medium (not shown), and reproduces the signal reproduced from the recording medium. A signal processing circuit that performs error correction or correction on a signal according to a predetermined conversion pattern, 6 is a D / A converter that converts a digital output signal processed by the signal processing circuit 5 into an analog output signal,
Reference numeral 7 is an output terminal for an analog output signal.

The internal configuration of the signal processing circuit 5 is, for example, Japanese Patent Laid-Open No. 58-8.
As shown in FIG. 3 of the drawings attached to the publication 0112,
A simplified version of this is shown in FIG. In FIG. 5, is connected to the output of the A / D converter 2,
Is connected to the control signal of the controller 15. Is an output, and is connected to a recording medium.

Reference numeral 8 is a peak hold circuit that peak-holds the digital output signal processed by the signal processing circuit 5 at predetermined time intervals, and 10 is a level display of the output data of the peak hold circuit 8 with preprogrammed memory data. Is a buffer circuit for supplying the output data of the level data conversion circuit 10 to the level indicator, and 14 is a level indicator.

15 is a controller composed of a CPU (not shown),
The data processing of the signal processing circuit 5 is controlled.

During normal recording by the magnetic recording / reproducing apparatus, the analog signal supplied to the input terminal 1 is converted into a digital signal by the A / D converter 2. The digital signal converted by the A / D converter 2 is signal-processed by the signal processing circuit 5, and the D / A converter 6
Is output to the output terminal 7 after being converted into an analog signal. This analog output signal is reproduced through an amplifier and a speaker (not shown).

On the other hand, the signal-processed output data of the signal processing circuit 5 is supplied to the peak hold circuit 8, and the peak value of the output signal is held.

The peak hold circuit 8 holds the peak data for a predetermined time, for example, 2 seconds (or 3 seconds), is reset after 2 seconds, and holds the next new output data again for 2 seconds.

The hold data thus peak-held is supplied to the level data conversion circuit 10, converted by the level display program, and displayed on the level indicator 14 via the buffer circuit 13.

The output level indicator 14 is adapted to illuminate and display a segment in the form of a display bar that matches the level scale from OdB to −∞ (see FIG. 3). Also, the output offset of the A / D converter 2 is shown. When adjusting the voltage, the input terminal 1 is set to the grounded state and adjusted by the offset adjuster 4. Generally, since the A / D converter 2 always has an offset, it is necessary to adjust the offset.

Monitor the A / D converter 2, connect a high-sensitivity voltmeter (not shown), etc. to the output terminal 7 and measure the offset voltage value appearing on the output side of the A / D converter. The offset adjuster 4 adjusts so that

At this time, the output level indicator 14 cannot display a minute offset voltage value, and the display bar segment of −∞ dB lights up.

(C) Problems to be solved by the device However, in the adjustment of the output offset voltage of the A / D converter such as the digital recording / reproducing device described above, it is impossible to directly read the output offset voltage in the display range of the output level indicator. However, there is a drawback that the offset voltage value must be measured by connecting a high-sensitivity voltmeter of another device to the output terminal.

For this reason, there has been a drawback that a lot of time is spent on the offset adjustment and the cost is increased.

The present invention has been made in view of the above points, and an object thereof is to provide a level display device such as a digital recording / reproducing device that solves the drawbacks of the conventional example.

(D) Means for solving the problem The level display device of this invention is an A / D converter having an output offset adjusting means, a peak hold circuit for peak-holding this output digital signal, and a peak-hold level for converting the peak-hold level. In a level display device composed of a level data conversion circuit for displaying a predetermined level and a display device for displaying output data of the level data conversion circuit, the level data conversion circuit displays the level at a normal time. The first level data conversion circuit includes a first level data conversion circuit, a second level data conversion circuit for displaying a level at the time of offset adjustment of the A / D converter, and a switch and a controller for performing the offset adjustment. The second level data conversion circuit and a switching device for switching.

Further, the first and second level data conversion circuits may be replaced with first and second ROM tables stored in the ROM as a program memory.

Further, at the time of offset adjustment, display characters for confirming the offset adjustment operation can be displayed on the level indicator.

It is also possible to provide a switching device for short-circuiting the input terminals of the A / D converter, and to provide switching means for switching control by the controller during offset adjustment.

(E) Function In the level display device of the magnetic recording / reproducing apparatus, the level display during normal recording / reproducing operation is such that the input signal level is displayed on the level display by the memory data programmed in the first level data conversion circuit. It This level indicator has a level scale from OdB to -∞, and a display bar segment lights up to display the output level.

On the other hand, the level display during offset adjustment of the A / D converter is displayed by the memory data programmed in the second level data conversion circuit. This level display is above
The level scale from OdB to -∞ is set to high sensitivity as shown in Fig. 2, and the offset level of the A / D converter can be displayed sufficiently.

The level display during normal operation and the level display during offset adjustment are controlled by a switch and a controller for offset adjustment. At the time of offset adjustment, the input terminal of the A / D converter is short-circuited and the first and second
The level data conversion circuit is switched.

Further, at the time of offset adjustment, a display character for confirming the offset adjustment operation can be displayed on the level display by controlling the controller.

(F) Embodiment An embodiment of the level display device according to the present invention will be described with reference to FIGS. 1 and 3.

FIG. 1 is a block diagram of the present invention, FIG. 2 is a characteristic diagram of input sensitivity showing a relationship between a level scale of a level indicator and an input level, and FIG. 3 is a level display diagram of a level indicator. .

The same parts as those in the conventional example are designated by the same reference numerals and the description thereof will be omitted.

In the figure, 3 is a short-circuiting switch on the input side of the A / D converter 2 for adjusting the offset voltage of the A / D converter 2, 9 and 12 are hold output data peak-held by a peak hold circuit by a controller 15. A switching device for controlling and switching, 10 is a first level data conversion circuit for converting the peak hold output data by preprogrammed memory data so as to display the level, and 11 is a second level data conversion circuit for the first level data conversion circuit. Level data conversion circuit
The same operation as 10 is performed, but the contents of converting the level data are different.

16 is a test switch for offset adjustment that is operated when performing offset adjustment, and 17 is a controller 15
Is a display driver circuit for displaying characters on the level indicator 14 when the offset is adjusted.

When the magnetic recording / reproducing apparatus performs a normal recording or reproducing operation, the offset adjusting test switch 16 is OFF, and the input side short-circuiting switch 3 is also OFF.

The analog signal supplied to the input terminal 1 is converted into a digital signal by the A / D converter 2, and this input signal is supplied to the switch 9 via the signal processing circuit 5 and the peak hold circuit 8.

The switch 9 is controlled by the controller 15 and connected to the a contact, and the peak hold output data is supplied to the first level data conversion circuit 10 via the a contact of the switch 9.

The first level data conversion circuit 10 stores a program for displaying the normal level. The peak hold output data is converted into level display data by this memory data, and is supplied to the level display 14 through the a contact of the switch 12 and the buffer circuit 13 to display the peak level.

Also, when the offset adjustment test switch 16 is turned on,
This digital recording / reproducing apparatus is set to the offset adjustment state of the A / D converter 2, and the controller 15 turns on the short-circuiting switch 3 connected to the input terminal 1 to ground the input of the A / D converter 2 and at the same time. Switch 9 and 12 b
Connected to the contact, the output data of the peak hold circuit 8 is supplied to the second level data conversion circuit 11.

A program for displaying the offset level at the time of offset adjustment is stored in the second level data conversion circuit 11, and the offset is displayed on the level indicator 14.

On the other hand, the controller 15 causes the display driver circuit 17 to "TEST".
Supply the signal data of character display, and this display driver circuit
17 drives the "ST" terminal of level indicator 14.

FIG. 2 is a characteristic diagram showing the relationship between the input level of the input signal supplied to the input terminal 1 and the level scale of the level indicator 14.

Further, FIG. 3 is a level display diagram of the level display unit. The level display unit 20 of the level display unit 14 displays, for example, the segment 2 for displaying the L and R channel levels of the audio output level.
1, 22 and OdB to --∞ level scales 23, 24 and `` OV
ER ”scale character 25. Further, 26 is a "TEST" character display which is lit when the offset is adjusted. The level scales 23 and 24 are the numerical display 23 from OdB to -∞,
The space between the numeral displays 23 is omitted by a "." The level display during normal recording or playback has the relationship of (a) linear input level vs. level scales 23 and 24 in the input sensitivity characteristic of FIG.
In the case of dB, the segments 21 and 22 of the display bar type are lit up to the position of -50 dB of the level scales 23 and 24 from the smallest level and the level is displayed. Also, when the input level is OdB or higher, "OVER" 25 characters are displayed.

The level display at the time of offset adjustment is set by the second level data conversion circuit 11 so that the relationship between the input level and the level scales 23 and 24 of the straight line in FIG.

The straight line in FIG. 2 (b) is set to high sensitivity so that the offset voltage of the A / D converter 2 can be adjusted. For example, at the −60 dB scale position of the level scales 23 and 24, −x dB (−70 to −9).
OdB) is set. In addition, the level display range of the straight line (b) is generally limited to a minute voltage range of −20 dB in the level scales 23 and 24, and the input level is −y dB.
(Eg -30 to -50 dB).

In this way, since the output offset voltage is displayed in the relationship of the straight line (b), during the offset adjustment, the offset adjuster 4 should be adjusted so that the offset voltage becomes zero while observing the display level of this offset minute voltage. You can

Thus, the first and second level data conversion circuits 10, 11
The level display can be switched between the normal level display and the offset level display in which the input level sensitivity of the level display is increased by using one level display 14 according to the purpose.

A ROM table can be used in the level data conversion circuit described above. That is, the first level data conversion circuit 10 is replaced with the first ROM table, and the second level data conversion circuit 11 is replaced with the second ROM table.

This ROM table stores the data programmed in the ROM in advance according to the purpose and outputs the input data according to the purpose.

As described above, the output signal of the peak hold circuit 8 is supplied to the first or second ROM table via the switch 9. The ROM table displays the above input data as a level indicator 14
Converted to signal data for display in the buffer circuit
It outputs to the level indicator 14 through 13.

In this way, the ROM table can be converted into display data and the level display 14 can perform the intended display.

(G) Effect of the device According to the level display device such as the digital recording / reproducing device according to the present invention, the A / D converter is provided by using this one level display
Since the level of the minute offset output voltage of the converter can be displayed, there is an effect that the offset voltage can be adjusted while directly reading the offset output voltage.

For this reason, another measuring device such as a high-sensitivity voltmeter becomes unnecessary, and the offset adjusting process can be simplified, and the cost can be reduced.

In addition, it has excellent features such as a simple structure and a low cost, which makes it easy to implement.

[Brief description of drawings]

1 to 3 show an embodiment of a level device according to the present invention, FIG. 1 is a block diagram of a level display device such as a digital recording / reproducing device, and FIG. 2 is an input level and a level scale of a level indicator. FIG. 3 is a characteristic diagram showing the relationship with, and FIG. 3 is a display diagram of the level indicator. FIG. 4 is a block diagram of a conventional example. FIG. 5 is a block diagram of the signal processing circuit 5 in FIGS. 1 and 4. Explanation of main numbers 2: AD converter 3: Input side short-circuit switch 4: Offset adjuster 5: Signal processing circuit 6: DA converter 8: Peak hold circuit 9, 12: Switch 10: First level data conversion Circuit 11: Second level data conversion circuit 14: Level indicator 15: Controller 16: Offset adjustment test switch 17: Display drive circuit 20: Level display section 21, 22: Display bar segment 23, 24: Level scale 26 : "TEST" character display

Claims (4)

[Scope of utility model registration request] 1. An A / D converter having an output offset adjusting means, a peak hold circuit for peak-holding the output digital signal, and a level data conversion circuit for converting the peak hold level to display a predetermined level. And a display device for displaying output data of the level data conversion circuit, wherein the level data conversion circuit displays a level at a normal time, and the A / D A second level data conversion circuit for displaying a level when the offset of the converter is adjusted, and a switch for switching between the first level data conversion circuit and the second level data conversion circuit by a switch and a controller for adjusting the offset. A level display device characterized by being configured with. 2. The level display device according to claim 1, wherein the first and second level data conversion circuits are composed of first and second ROM tables stored in a ROM as a program memory. 3. The level display device according to claim 1, wherein a display character for confirming the offset adjustment operation is displayed on the level indicator during the offset adjustment. 4. A level display circuit according to claim 1, further comprising switching means for short-circuiting the input terminals of the A / D converter, and switching means for switching control by the controller during offset adjustment. .