JPH0570168B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an offset setting device for setting a predetermined offset value for sequentially input input signals, and more particularly, the present invention relates to an offset setting device for setting a predetermined offset value for input signals that are input sequentially, and more particularly, The present invention relates to an offset setting device that calibrates deviations due to accuracy of a digital converter, etc. when setting an offset value for a signal, and performs accurate offset setting.

[Conventional technology]

For example, in a waveform recorder, it is a display means.
A desired offset level is often set and displayed on the screen of a CRT. Conventionally, the offset value is set in an analog way using a visual operation such as adjusting a volume knob or the like to align the offset level signal line displayed on the screen with a predetermined grid. There were many.

On the other hand, with the development of digital technology, a method has been proposed in which such offset setting is performed digitally by a central processing means (hereinafter referred to as CPU) such as a microcomputer. Such a digital offset setting device instructs the CPU to set an offset value as a desired percentage value or a numerical value such as a voltage value, and the CPU converts the digital value corresponding to the offset value into a digital-to-analog converter (hereinafter referred to as D). /A converter), where it is converted to an analog value, and this analog offset value is added to the signal input line before entering the amplifier, and the value is added to the analog-to-digital converter (hereinafter referred to as A/D converter). The offset value is converted into a digital value by a converter (referred to as a converter) and output as an offset value.

[Problem to be solved by the invention]

However, since the offset value from the CPU passes through the D/A converter, amplifier, and A/D converter, there may be a difference between the set offset value and the final offset value from the A/D converter depending on their accuracy. There may be deviations between the two. Therefore, for example, even if there is a grid at the 50% position on the screen of a CRT and the offset value is set to 50%, the offset may not fall on this 50% grid.

Therefore, an object of the present invention is to compare the offset value obtained by the A/D converter with a predetermined instructed offset value, and if there is a difference, perform calibration to prevent the above-mentioned deviation. An object of the present invention is to provide an offset setting device as described above.

[Means to solve the problem]

In order to display the offset value numerically set by the control means on the analog input signal, the present invention converts the offset value into an analog signal using a D/A converter, and converts the offset value into a digital signal together with the input signal using the A/D converter. In the offset setting device, a reference value creation means that creates a reference digital value corresponding to a numerical value compares the offset value from the analog/digital converter with the reference digital value from the reference value creation means, and determines whether the offset value is within a predetermined tolerance range. a correction value generating means for instructing the control means to store the offset value when the offset value is within the allowable range, and setting a correction value when the offset value is not within the allowable range; It has a calibration offset output means for setting a calibration offset value and sending the calibration offset value from the digital/analog converter to the correction value creation means to compare the calibration offset value and the reference digital value again, The correction value creation means is characterized in that when the offset value for calibration reaches within a predetermined tolerance range, it instructs the control means to store the offset value for calibration.

[Effect]

Therefore, the correction value creation means compares the offset value set by the control means with the digital value when passing from the D/A converter to the A/D converter and determines whether or not it is within a predetermined tolerance range. If it is not within the allowable range, the offset value for calibration is set using the calibration offset output means, and the data is passed from the D/A converter to the A/D converter again for comparison. Through such processing, a digital value corresponding to a predetermined offset value can be set.

〔Example〕

An embodiment of the present invention shown in the drawings will be described below. In this embodiment, a waveform recorder is taken as an example. Input terminal 1 to which the measurement input signal is applied is connected to switch 2 for offset setting.
The adder 3 is connected to the adder 3 via the adder 3. The output side of the adder 3 is connected to the CPU 7 via an amplifier 4, an A/D converter 5, and a correction value generating means 6.
The operating program was written into CPU7.
ROM8, stores setting conditions such as offset values, etc.
A RAM 9 and display means 11 such as a CRT, a liquid crystal display device, or a printer are connected.
The CPU 7 also includes an offset setting means 12 for setting an offset value numerically, which is comprised of, for example, a numeric keypad, and offset value data set by the offset setting means 12.
A reference value creation means 13 is connected to receive the reference value from the reference value and create an offset reference value. The output side of the reference value creation means 13 is connected to the correction value creation means 6. When setting the offset, the correction value creation means 6 compares the offset value from the A/D converter 5 with the offset reference value from the reference value creation means 13, and creates a correction value if they do not match.
A calibrated offset output means 14 that outputs a calibration offset value based on the correction value is connected to the correction value creation means 6, and the calibrated offset output means 14 is connected to the CPU 7 and the D/A converter 15. There is. The D/A converter 15 is initialized by the CPU 7 in accordance with an initialization instruction from the CPU 7.
is also connected to the adder 3, and its output side is connected to the adder 3.

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG. First, after switching the offset setting switch 2 to the ground side, devices such as the A/D converter 5, RAM 9, and D/A converter 15 are initialized. The switch 2 may be turned on and off manually or by the CPU 7. This leaves the input in a shot state. In this state, the offset setting means 12 is operated to indicate a desired offset value numerically. The CPU 7 sends the value to the reference value creation means 13. In addition, the CPU 7 uses the D/A converter 15 as a calibration variable for this value.
Initialize. In the reference value creation means 13, the value that should be obtained when sampling is performed by the D/A converter 15 using this set offset value is set in advance as a reference value, and this value is used as the correction value creation means. Send to 6. The correction value creation means 6 sends a value in which the correction value for the D/A converter 15 is zero in the initially set offset value to the calibrated offset output means 14, and the calibrated offset output means 14 outputs the value. The signal is sent to the D/A converter 15, converted into an analog value, and then added to the adder 3. The output from the adder 3 is amplified by an amplifier 4 and then sampled by an A/D converter 5. This sampling value is added to the correction value creation means 6 and compared with the reference value of the reference value creation means 13. When the sampling value is equal to the reference value or within a preset allowed tolerance range, the correction value creation means 6
gives an instruction to store the calibration value in the RAM 9 of the CPU 7, and upon receiving this, the CPU 7 reads out the calibration value from the calibrated offset output means 14.
Store in RAM9.

On the other hand, as a result of the comparison, if the sampled value is not equal to the reference value, the correction value creation means 6 sends the information to the calibrated offset output means 14. In the calibrated offset output means 14, when the sampled value is higher than the reference value as a result of the comparison, the value applied to the D/A converter 15 is adjusted so as to lower the sampled value obtained by the A/D converter 5. Make it smaller than last time. Further, when the sampling value is lower than the reference value, the value applied to the D/A converter 15 is made larger than the previous value so as to increase the sampling value obtained by the A/D converter 5. With the value set again in this way, the sampling value obtained by the A/D converter 5 is compared with the reference value of the reference value creation means 13 by the correction value creation means 6, and the result is checked. When the sampling value is equal to the reference value or within a preset tolerance range, the correction value creation means 6 issues an instruction to store the calibration value in the RAM 9 of the CPU 7. Thereby, the CPU 7 reads out the calibration value from the calibrated offset output means 14 and stores it in the RAM 9. After the offset value has been calibrated in this way, the offset setting switch 2 is closed and a waveform signal is input from the input terminal. Thereby, the waveform can be displayed on the display means 11 together with the offset line displayed on the grid at a predetermined position.

In the above embodiment, the correction value creation means 6, the offset setting means 12, the reference value creation means 13, and the calibrated offset output means 14 are provided separately from the CPU 7, but these functions can be performed by the CPU 7. You can do it like this. Further, the switch 2 for shorting the input when setting the offset may be monitored by the CPU 7 instead of the coupler.

〔Effect of the invention〕

As described above, the offset setting device of the present invention combines a numerically specified offset value with an analog input signal, so that the accuracy of the D/A converter, A/D converter, etc. in which the offset value is processed can be improved. Even if the value fluctuates due to factors such as the Can be displayed and recorded.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a flowchart for explaining its operation. In the drawing, 1 is an input terminal, 2 is an offset setting switch, 3 is an adder, 4 is an amplifier, 5 is an A/D converter, 6 is a correction value creation means, 7 is a CPU,
8 is ROM, 9 is RAM, 11 is display means, 12
13 is an offset setting means, 13 is a reference value creation means,
14 is a calibrated offset output means, 15 is a D/A
It is a converter.

Claims (1)

[Claims] 1. In order to display the offset value numerically set by the control means on the analog input signal, the offset value is converted into analog by a digital/analog converter, and the offset value is converted into digital by the analog/digital converter together with the input signal. In the setting device, a reference value creation means for creating a reference digital value corresponding to the numerical position compares the offset value from the analog/digital converter with the reference digital value from the reference value creation means, and determines a predetermined value. correction value creation means for instructing the control means to store the offset value when the offset value is within the tolerance range, and setting a correction value when the offset value is not within the tolerance range; A calibration offset value is set according to the correction value, and this calibration offset value is sent from the digital/analog converter to the correction value creation means, and the calibration offset value and the reference digital value are compared again. and a calibration offset output means for the calibration, and the correction value creation means instructs the control means to store the calibration offset value when the calibration offset value reaches a predetermined tolerance range. Characteristic offset setting device.