JPH05172853A - Calibration device for vertical amplifier for multirace oscilloscope - Google Patents

Abstract

PURPOSE:To allow each input/output characteristic of both the variable gain amplifiers to correctly accord each other by adjusting the gain and offset by simultaneously supplying the equal voltage to two variable gain amplifiers. CONSTITUTION:The output voltage of a standard voltage generator 21 is simultaneously supplied into variable gain amplifiers 9 and 10. The polarity of the output electric current of the variable gain amplifier 10 is reversed by a selector switch 31. The output electric current having the reversed polarity and the output electric current of the variable gain amplifier 9 are added by an adding circuit 32. The result of the addition is detected by a resistor 15. A CPU 18 takes in the result of the detection, and controls each gain of both the variable gain amplifiers 9 and 10 so that the detection value becomes zero. Further, the CPU 18 supplies the signal at the grounding level to the variable gain amplifiers 9 and 10, and controls each offset of the variable gain amplifiers 9 and 10 so that the addition result detected by the resistor 15 becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical amplifier calibration device for a multi-phenomenon oscilloscope, and more particularly to a vertical amplifier calibration device for making input / output characteristics of variable gain amplifiers of input circuits of respective channels the same. ..

[0002]

2. Description of the Related Art A variable gain amplifier provided in each input circuit of a multi-phenomenon oscilloscope is adjusted so that whichever input circuit receives the same signal, the input signal is appropriately amplified and displayed. There is. Then, such adjustment is generally performed at the time of shipping or maintenance.

FIG. 1 is a block diagram showing the structure of a conventional device of this type.

In FIG. 1, 1 is a channel 1 (CH
1) signal input terminal, 2 is channel 2 (CH2) signal input terminal, 3 to 6 are variable attenuators, 7 and 8 are buffer amplifiers, 9 and 10 are variable gains that output a current proportional to the input voltage. It is an amplifier. 30 is a cathode ray tube (hereinafter, CRT)
Select signal S for inputting the signal to be displayed on 11)
A multiplexer that selects according to SO, 12 is an amplifier for driving a CRT, 13 is a gain adjuster of the amplifier 12, and 14 is an output offset adjuster of the amplifier 12. Reference numeral 15 is a resistor for detecting the value of the current input to the amplifier 12, 1
Reference numeral 6 denotes an analog / digital converter for converting the detected current value into a digital signal, and the output signal of the analog / digital converter 16 is sent to the CPU 18 via the bus gate 17. Reference numeral 19 is a memory for storing data and the like.

Reference numeral 20 is an input signal selector for selecting a signal to be output to each variable gain amplifier 9, 10 according to a select signal SSI output from the CPU 18, and 21 is for generating a signal for calibrating the variable gain amplifier 9, 10. It is a standard voltage generator. 22 to 25 are latches, and 26 to 29 are digital-analog converters, and the CPU 18 supplies the gain control signals GC1 and GC2 and the position (offset) to the variable gain amplifiers 9 and 10 via these latches and digital-analog converters. The control signals PC1 and PC2 are transmitted.

In the conventional example configured as described above,
During normal signal measurement, the CPU 18 selects the select signal SS
I is used to select the terminals d and d'of the input signal selector 20. Therefore, terminals 1 and 2 are connected to the variable gain amplifiers 9 and 10, respectively.
The signal under measurement to be input to is supplied. And CPU1
8 uses the select signal SSO to output the multiplexer 30
By alternately selecting terminals a and a'and terminals b and b'of the CRT 11
To display.

Next, the operation of calibrating the variable gain amplifiers 9 and 10 will be described.

When the variable gain amplifiers 9 and 10 are calibrated, the CPU 18 uses the select signal SSI to select the terminals e and e'of the input signal selector 20. At this time, the variable attenuators 5 and 6 are set to a predetermined attenuation ratio. In such a state, the standard voltage Vr is applied to the variable gain amplifiers 9 and 10.
ef will be supplied.

First, when calibrating the variable gain amplifier 9, the CPU 18 can select the terminals a and a'of the multiplexer 30 using the select signal SSO to detect the value of the output current I ₁ of the variable gain amplifier 9. To do so. Then, as shown in FIG. 2, the value of the output current I ₁ is a predetermined value I _0.
The slope of the input / output characteristic is adjusted by the gain control signal GC1 so that

Next, the CPU 18 uses the select signal SSI to select the terminals f and f'of the input signal selector 20 and supplies the earth signal (OV) to the variable gain amplifier 9 as a reference voltage for offset adjustment. Then, as shown in FIG. 2, the position control signal PC1 is set so that the value of the output current I ₁ becomes zero.
Adjust the position (offset) of input / output characteristics by.

As is apparent from FIG. 2, when the gain of the variable gain amplifier 9 is changed so that the output current becomes I ₀ when the input voltage is Vref, the output current value at the time of OV input ( The offset) _If also changes.
Conversely, when changing the position (offset) I _f at OV input, the input voltage with it will also change the value of the output current when the Vref. Therefore, the CPU 18 alternately repeats the gain adjustment and the position (offset) adjustment until the predetermined input / output characteristic shown by the broken line in FIG. 2 is obtained.

When the calibration of the variable gain amplifier 9 is completed as described above, the CPU 18 uses the select signal SSO to select the terminals b and b'of the multiplexer 30, and the variable gain amplifier 10 has the same processing as that previously performed. Calibrate by the process of.

After the calibration of the variable gain amplifiers 9 and 10 is completed, both of them have the predetermined input / output characteristics shown by the broken line in FIG.

Here, the user operates the CPU 18 to
The terminals a and a'or the terminals b and b'of the multiplexer 30
Is selected, and the output of either one of the variable gain amplifiers 9 and 10 is supplied to the CRT driving amplifier 12. And CP
The earth signal (OV) is selected by operating the U18 to cause the input signal selector 20 to select the terminals f and f ', and the output offset is provided while observing the screen so that the signal is displayed at a predetermined position on the display surface of the CRT 11. Adjust the adjuster 14. Next, the user operates the CPU 18 to cause the input signal selector 20 to select the terminals e and e ', and then the standard voltage Vref.
Is supplied to the variable gain amplifiers 9 and 10, and the signal is a CRT.
The gain adjuster 13 is adjusted so that it is displayed at a predetermined position different from the predetermined position ahead of 11. Then, the above adjustment is repeated until both the ground signal and the standard voltage Vref are displayed at the predetermined positions. By operating the gain adjuster 13 and the output offset adjuster 14 as described above, each CR
The gain and output offset of the entire vertical amplification system are finally determined so that the input signal is displayed properly according to the characteristics of T.

[0015]

By the way, the accuracy of calibrating the variable gain amplifiers 9 and 10 is defined by the analysis capability of the analog-digital converter 16. Here, when the allowable error due to the analysis capability of the analog-digital converter 16 is ± ε, there is a possibility that the input / output characteristics of both variable gain amplifiers 9 and 10 in the above conventional example will shift as shown in FIG. There is. That is, in the above-mentioned conventional example, there is a possibility that the output offset (when the ground signal is input) is shifted by 2ε and the gain is shifted by 4ε / Vref.

Further, in the above conventional example, when the output voltage of the standard voltage generator 21 fluctuates between the calibration of the variable gain amplifier 9 and the calibration of the variable gain amplifier 10,
There is a problem that the input and output characteristics of both variable gain amplifiers 9 and 10 do not match even after the adjustment is completed. That is, in the above-described conventional example, in such a case, even if the same signal is input to each channel after the adjustment is completed, the same waveform may not be displayed on the display surface of the CRT 11.

It is an object of the present invention to provide a vertical amplifier calibration device for a multi-phenomenon oscilloscope which can match the input / output characteristics of the variable gain amplifier with high accuracy even if the output of the standard voltage generator fluctuates. It is in.

[0018]

In order to achieve the above object, the present invention provides a plurality of variable gain amplifiers, each of which is provided as a vertical amplifier for amplifying an input signal in each input stage of a multi-phenomenon oscilloscope. Output polarity switching means provided on the output side of the first variable gain amplifier, addition means for adding the output of the output polarity switching means and the output of the second variable gain amplifier, and the output of the addition means Detecting means, a standard voltage generating means for generating a standard voltage, and the standard voltage are simultaneously supplied to the first and second variable gain amplifiers so that the output of the detecting means becomes zero. Gain control means for controlling the gain of at least one of the first and second variable gain amplifiers, reference voltage generation means for generating a reference voltage having a value different from the standard voltage, and the reference voltage 1 and the second variable gain amplifier at the same time, and offset control means for controlling the offset of at least one of the first and second variable gain amplifiers so that the output of the detection means becomes zero. It is characterized by

[0019]

According to the present invention, the output voltage of the standard voltage generating means is simultaneously output to the first and second variable gain amplifiers. The polarity of the output of the first variable gain amplifier of the variable gain amplifiers is inverted by the polarity inversion means. In this way, the adding means adds the two outputs having different polarities, and the detecting means detects the result.
The gain control means controls the gain of at least one of the two variable gain amplifiers so that the output of the detection means becomes zero.

Next, the output voltage of the reference voltage generating means is the first
And simultaneously output to the second variable gain amplifier. The polarity of the output of the first variable gain amplifier of the variable gain amplifiers is inverted by the polarity inversion means. In this way, the adding means adds the two outputs having different polarities, and the detecting means detects the result. The offset control means controls the offset of at least one of the two variable gain amplifiers so that the output of the detection means becomes zero. By repeating the above processing, the gain and offset of both variable gain amplifiers match, and the input / output characteristics of both variable gain amplifiers match.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram showing the configuration of an embodiment of the present invention, and the same reference numerals as those in FIG. 1 denote the same components. Reference numeral 31 is a changeover switch for switching the polarity of the output of the variable gain amplifier 10, which is normally connected to the terminals g and g '. When the CPU 18 outputs the inverted signal INV, it is connected to the terminals h and h'. Reference numeral 32 denotes an adder circuit for combining the output currents I ₁ and I ₂ of the variable gain amplifiers 9 and 10, and when the addition signal ADD is output from the CPU 18, the switch is closed and the addition current is added to the terminal C of the multiplexer 30.
It is supplied to the amplifier 12 from C '. Changeover switch 3 here
1 and the adder circuit 32 are usually provided in the conventional multi-phenomenon oscilloscope.

In the present embodiment constructed as described above, the terminals d and d'are selected in the input signal selector 20 and the changeover switch 31 is connected to the terminals g and g'during normal signal measurement. Therefore, the switch of the adding circuit 32 is open. Therefore, similarly to the conventional example, the CPU 18 uses the select signal SSO to connect the terminals a,
The signals input to the terminals 1 and 2 are displayed on the CRT 11 by alternately selecting a'and terminals b and b '. In such a state, when the operator operates the CPU 18 to output the inverted signal INV, the changeover switch 31 is connected to the terminals h and h ', and the polarity of the signal input to the terminal 2 is reversed so that the CRT 11 Displayed in. Further, when the operator causes the CPU 18 to output an addition signal, the addition circuit 32
Switch is closed, and the terminals c and c'of the multiplexer 30 are selected by the select signal SSO.
The difference between the signal input to the terminal and the signal input to terminal 2 is the CRT.
11 will be displayed.

In this embodiment, such a changeover switch 31 is used.
And the adder circuit 32 are used to match the input / output characteristics of the variable gain amplifiers 9 and 10 with high accuracy. When calibrating the variable gain amplifiers 9 and 10, the CPU 18 performs the processing described below according to the processing procedure stored in the memory 19 in advance.

FIG. 5 is a flow chart showing the operation to be executed by the CPU 18 when calibrating the variable gain amplifier. In this calibration process, the two outputs when the reference voltage is supplied to the two variable gain amplifiers are matched using the position (offset) control signal, and the two outputs when the standard voltage is supplied are matched using the gain control signal. By doing so, the input and output characteristics of both variable gain amplifiers are made to match.

Before executing the processing procedure of FIG. 5, the damping ratio of the variable attenuator 5 and the variable attenuator 6 is set to a predetermined damping ratio.

In step S1, the CPU 18 uses the select signal SSI to connect the terminals f and f'of the input signal selector 20.
To output the inversion signal INV and select the switch 31
Are connected to terminals h and h ', and the addition signal ADD is output to close the switch of the addition circuit 32 and select signal S
The terminals c and c'of the multiplexer 30 are selected by using SO. In such a state, the variable gain amplifier 9,
A ground signal (OV) is supplied to 10 as a reference voltage for adjusting the difference between both offsets, and a resistor 15
Therefore, the difference between the output currents of the variable gain amplifiers 9 and 10 (I
_1- I ₂ ) is detected.

In step S2, the output (I ₁ -I ₂ ) of the adder circuit 32 detected by the resistor 15 is fetched through the analog / digital converter 16 and the bus gate 17.

In step S3, it is determined whether or not the output of the adder circuit 32 is zero. If it is not zero, the process proceeds to step S4.

In step S4, the value of the position control signal PC1 or PC2 is increased by a predetermined amount.

Next, returning to step S2, the output of the adding circuit 32 is fetched, and it is judged whether or not the value is zero (step S3). If it is not zero, the process returns to step S4 again.

In step S4, the previous output value and the current output value are compared, and if the current output value is closer to zero than the previous output value, it is the same as the previous processing. Then, the value of the position control signal PC1 or PC2 is increased by a predetermined amount. Conversely, when the output value of the previous time is closer to zero than the output value of this time, the gain control signal PC1 or PC
The value of 2 is decreased by a predetermined amount. Thus, in step S4, the position (offset) of the input / output characteristic of the variable gain amplifier 9 or 10 is adjusted using the position control signal PC1 or PC2.

The above steps S2 to S4 are repeated until a positive determination is made in step S3. When an affirmative determination is made in step S3, the process proceeds to step S5.

In step S5, the CPU 18 selects the terminals e and e'of the input signal selector using the select signal SSI and supplies the standard voltage Vref to the variable gain amplifiers 9 and 10.

In step S6, the difference (I) between the output currents of the variable gain amplifiers 9 and 10 detected by the resistor 15 is detected.
_1- I ₂ ) is taken in.

In step S7, the output current difference (I ₁ −
I ₂ ), that is, whether the output of the adder circuit 32 is zero or not. If it is not zero, the process proceeds to step S8.

In step S8, the value of the gain control signal GC1 or GC2 is increased by a predetermined amount.

Next, returning to step S6, the output of the adding circuit 32 is fetched, and it is judged whether or not the value is zero (step S7). If it is not zero, the process returns to step S8 again.

In step S8, the previous output value and the current output value are compared, and if the current output value is closer to zero than the previous output value, it is the same as the previous processing. Then, the value of the gain control signal GC1 or GC2 is increased by a predetermined amount. On the contrary, when the output value of the previous time is closer to zero than the output value of this time, the gain control signal GC1 or GC is reversed, contrary to the processing of the previous time.
The value of 2 is decreased by a predetermined amount. In this way, in step S8, the gain (gradient) of the input / output characteristic of the variable gain amplifier 9 or 10 using the gain control signal GC1 or GC2.
Adjust.

The above steps S6 to S8 are repeated until a positive determination is made in step S7. When an affirmative decision is made in step S7, the operation proceeds to step S9.

As described above, in the variable gain amplifier, when the gain is changed, the position (offset) at the time of OV input changes, and conversely, when the position (offset) is changed, the output value at the time of Vref input also changes. Therefore, it is determined whether the position (offset) or the gain is adjusted in step S4 or step S8 (step S9). Then, when the adjustment is performed, the processes of steps S1 to S9 are repeated.

If it is determined in step S9 that neither the position (offset) nor the gain has been adjusted, the process proceeds to step S10 and the control signals GC1, PC1, GC2, PC2 output to the variable gain amplifiers 9, 10 are controlled. Value in memory 19
And store the output value.

As described above, the variable gain amplifiers 9 and 10 are
FIG. 6 shows the maximum deviation of the input / output characteristics of both variable gain amplifiers 9 and 10 when calibrated. Where ± ε is analog
This is the allowable error due to the analysis capability of the digital converter 16. As shown in FIG. 6, in the present embodiment, the output offset (when the ground signal is input) even when the output is shifted to the maximum
Is ε, and the gain is only 2ε / Vref. The reason is that, in this embodiment, the input / output characteristics of one variable gain amplifier serve as a reference when calibrating the other variable gain amplifier. Therefore, according to this embodiment, the error can be halved as compared with the conventional example shown in FIG.

After the calibration of the variable gain amplifiers 9 and 10 is completed, the user adjusts the output offset adjuster 14 and the gain adjuster 13 while looking at the screen of the CRT 11 in the same manner as in the conventional case, and adjusts the gain of the entire vertical amplification system. Finally determine the output offset. Since the final gain and the output offset are determined by the user in this way, even if the offset current flows when the earth signal (OV) is input as shown in FIG. The misalignment of will be eliminated by this final user adjustment.

As described above, in the present embodiment, since the same voltage is supplied to the variable gain amplifiers 9 and 10 at the same time, even if the output voltage of the standard voltage generator 21 fluctuates during the gain adjustment process, both are kept. The input / output characteristics of the variable gain amplifiers 9 and 10 can be matched with high accuracy.

Although the present embodiment is a two-phenomenon oscilloscope, for example, in the case of a four-phenomenon oscilloscope, the positions of the other three variable gain amplifiers are based on the variable gain amplifier of the second channel having the output inverting function. By adjusting the (offset) and the gain, the position (offset) and the gain of the input / output characteristics of all variable gain amplifiers can be matched with high accuracy. Further, in the case of calibrating the variable gain amplifier of the four-phenomenon oscilloscope, conventionally, it was necessary to perform calibration processing once for each amplifier, that is, four times in total, but according to this embodiment, calibration processing for all amplifiers is performed three times. The gains can be matched.

FIG. 7 is a block diagram showing the configuration of another embodiment of the present invention. The same reference numerals as those in FIG. 4 denote the same elements, and 33 is an inverting amplifier (gain = -1). is there. In the present embodiment, the polarity of the output voltage of the standard voltage generator 21 is inverted by the inverting amplifier 33 instead of the changeover switch and supplied to the variable gain amplifier 10, so that the polarity is opposite to that of the variable gain amplifier 9. The output of the variable gain amplifier 10 having the polarity of is added to the output of the variable gain amplifier 9. Therefore, the difference from the operation of the embodiment shown in FIG. 4 is step S of the flowchart shown in FIG.
The inversion signal INV is not output at 5 and the changeover switch 31 is connected to the terminals g and g '. Other configurations and operations are the same as those of the embodiment shown in FIG. 4, and therefore their explanations are omitted.

As described above, in the present invention, the means for inverting the polarity of the output of the variable gain amplifier when the standard voltage Vref is supplied may be provided on either the input side or the output side of the variable gain amplifier. Good.

[0049]

According to the present invention, since the same voltage is simultaneously supplied to two variable gain amplifiers to adjust their input / output characteristics, the input / output characteristics of both variable gain amplifiers can be matched with high accuracy. ..

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a conventional device.

FIG. 2 is an explanatory diagram for explaining adjustment of a variable gain amplifier.

FIG. 3 is an input / output characteristic diagram showing the accuracy of a conventional device.

FIG. 4 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

5 is a flowchart showing an example of a processing procedure of a CPU shown in FIG.

FIG. 6 is an input / output characteristic diagram showing the accuracy of the embodiment shown in FIG.

FIG. 7 is a block diagram showing the configuration of another embodiment of the present invention.

[Explanation of symbols]

 3, 4, 5, 6 Variable attenuator 7,8 Buffer amplifier 9,10 Variable gain amplifier 11 CRT 12 Amplifier 15 Current detection resistor 16 Analog-digital converter 18 CPU 19 Memory 20 Input signal selector 21 Standard voltage generation 22-25 Latch 26-29 Digital-analog converter 30 Multiplexer 31 Changeover switch 32 Adder circuit 33 Inverting amplifier

Claims (7)

[Claims] 1. An output provided on the output side of a first variable gain amplifier of a plurality of variable gain amplifiers provided as a vertical amplifier for amplifying an input signal at each input stage of a multi-phenomenon oscilloscope. Polarity switching means, adding means for adding the output of the output polarity switching means and the output of the second variable gain amplifier, detecting means for detecting the output of the adding means, and standard voltage generating means for generating a standard voltage. And the standard voltage is simultaneously supplied to the first and second variable gain amplifiers, and the gain of at least one of the first and second variable gain amplifiers is adjusted so that the output of the detection means becomes zero. Gain control means for controlling, reference voltage generating means for generating a reference voltage having a value different from the standard voltage, and supplying the reference voltage to the first and second variable gain amplifiers at the same time. And an offset control unit for controlling an offset of at least one of the first and second variable gain amplifiers so that the output of the detection unit becomes zero. apparatus. 2. The vertical amplifier for a multi-phenomenon oscilloscope according to claim 1, wherein the reference voltage generating means is a switch circuit that grounds the input terminals of the first and second variable gain amplifiers. Calibration device. 3. The vertical of the multi-phenomenon oscilloscope according to claim 1, wherein the output polarity switching means is an output polarity switching switch provided on the output side of the first variable gain amplifier. Amplifier calibration device. 4. A multi-phenomenon oscilloscope is provided, as a vertical amplifier for amplifying an input signal, with an input of an output of a first variable gain amplifier among a plurality of variable gain amplifiers respectively provided as vertical amplifiers for amplifying an input signal. Addition means for outputting the addition result with the input, detection means for detecting the output of the addition means, standard voltage generation means for generating the standard voltage, and output by inverting the polarity of the output voltage of the standard voltage generation means And a polarity reversing means for supplying the standard voltage to the first variable gain amplifier, an output of the polarity reversing means to a second variable gain amplifier, and an output of the second variable gain amplifier. The gain control means for controlling the gain of at least one of the first and second variable gain amplifiers so that the output of the detection means becomes zero as an input of Reference voltage generating means for generating a reference voltage having a value, output polarity switching means provided on the output side of the second variable gain amplifier, and the reference voltage for the first and second variable gain amplifiers. At least one of the first and second variable gain amplifiers so that the output of the output polarity switching means is supplied to the adder circuit as the other input and the output of the detection means becomes zero. A vertical amplifier calibration device for a multi-phenomenon oscilloscope, comprising: 5. The vertical amplifier of a multi-phenomenon oscilloscope according to claim 4, wherein the reference voltage generating means is a switch circuit that grounds the input terminals of the first and second variable gain amplifiers. Calibration device. 6. The vertical of the multi-phenomenon oscilloscope according to claim 4, wherein the output polarity switching means is an output polarity switching switch provided on the output side of the first variable gain amplifier. Amplifier calibration device. 7. The vertical amplifier calibration device for a multi-phenomenon oscilloscope according to claim 4, wherein the polarity inverting means is an inverting amplifier.