A channel gain calibration and display method capable of changing vertical scale numbers

Abstract

The present invention discloses a channel gain calibration and display method capable of changing the vertical scale number, which can change the quantization range of ADC (2 N , N = number of ADC bits), after removing the highest and lowest values ​​(closer to the upper and lower edges, the greater the error), the entire quantization value range is divided into M (M is a multiple of 2) segments, with 2 N / 2 is the center (which is equivalent to the 0 level of the AC signal), so that the amplitude value of the calibration signal after quantization falls at the set position. The channel gain control word obtained at this time is the calibration data to be obtained. Finally, the level scale and the corresponding level value of the quantization value of each ADC in each amplitude level are calculated and displayed with the required number of vertical scales.

Description

Technical Field

[0001] The invention belongs to the technical field of measuring instruments, and more specifically, relates to a channel gain calibration and display method capable of changing the vertical scale number. Background Art

[0002] The data acquisition system is mainly based on analog signal conditioning channels, ADC converters, data buffers and microprocessors. After the input measured signal is conditioned by the analog channel signal, the analog waveform is converted into a digital signal through the ADC converter and stored in the digital buffer. After that, the data is analyzed, decoded or displayed. In other words, it mainly includes three major steps: waveform signal conditioning → ADC quantization → waveform data display and processing.

[0003] As a data acquisition system, an important task is to calibrate the gain of the analog channel of the instrument. Calibration involves the entire process of the acquisition system. The basic idea of ​​calibration is to input the specified calibration signal, condition the input signal through the analog channel, and send it to the ADC for quantization. The software side determines whether the amplitude of the signal meets the requirements based on the analysis of the quantized data. If it does not meet the requirements, the gain control word of the analog channel is adjusted until the quantized amplitude is within the error range.

[0004] In the waveform observation display, the display area is generally divided into multiple grids. In mainstream oscilloscopes, it is generally divided into 8 grids (DIV) in the vertical direction. With the development of display devices, there is a display mode divided into 10 grids (DIV). During calibration, the current gear is generally used as the reference, and the input signal that can occupy 6 grids is used as the calibration signal.

[0005] However, in the actual use of the instrument, with a fixed display mode (8DIV or 10DIV), there are always some signals that are not well observed. If the ratio of the vertical height of the signal in the observation area to the entire visible area is defined as the vertical area view ratio (VAVR), the vertical area view ratio should be as large as possible (generally less than 80% is best). Figure 1 The comparison of vertical area visual ratios of different display modes is deduced from Table 1.

[0006]

[0007]

[0008] Table 1

[0009] From the above chart, it can be seen that in different situations, using different display modes, the optimal area display ratio is different.

[0010] In order to always obtain the best area display ratio, the display mode can be adjusted automatically or manually according to the amplitude of the measured signal to achieve the best observation effect.

[0011] However, the traditional gain calibration method is determined according to the display mode (8DIV mode, input 6DIV signal; 10DIV mode, input 8DIV signal). If the vertical display scale is changed, the traditional calibration method will be at a loss, or multiple sets of calibration data will need to be saved. Summary of the invention

[0012] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a channel gain calibration and display method with a changeable vertical scale number, so as to adapt to different display modes by calibrating the quantization amplitude of ADC.

[0013] To achieve the above-mentioned object of the invention, the present invention provides a channel gain calibration and display method with changeable vertical scale number, characterized in that it comprises the following steps:

[0014] (1) Segment the ADC quantization value;

[0015] Assume that the given quantization value range of ADC is 0 to 2 N -1, set the minimum value of the changeable vertical scale number to M;

[0016] According to the performance of the ADC and the performance of the analog channel, the highest and lowest values ​​of the ADC quantization value are removed, and 80% of the given quantization value range is retained, which is recorded as the applicable quantization range N;

[0017] Divide the applicable quantization range N into M segments, each segment contains m quantization words, m = N ÷ M, and m is an integer;

[0018] (2) Setting calibration criteria;

[0019] The calibration criterion is that the amplitude of the calibration signal occupies K segments out of M segments, that is, the amplitude of the calibration signal occupies K×m quantization words, K <M;

[0020] (3) Determine the amplitude of the calibration signal of each amplitude gear;

[0021] Assume that the current amplitude position to be calibrated is R, and the unit is V / DIV; then the amplitude value of the calibration signal output by the calibrator is K×R, and the unit is V;

[0022] (4) Calibration

[0023] The calibrator outputs the calibration signal to the analog channel. After the analog channel conditions the signal, it is input to the ADC for sampling. The signal sampled by the ADC is calculated to obtain the gain value of the sampled signal. If the gain value is equal to K×m quantization words, it indicates that the gear calibration is completed; otherwise, the gain control word of the channel is adjusted, and then the ADC is resampled and the gain value is calculated until the gain value is equal to K×m quantization words. The gear calibration is completed;

[0024] Calibrate each amplitude level in turn until all amplitude levels are calibrated;

[0025] (5) Waveform display when vertical scale number changes

[0026] After the calibration in step (4), the level scale D corresponding to the quantized value of each ADC in each amplitude range is calculated, where D = R ÷ m;

[0027] Assume that a certain quantization value in the actual sampling of the ADC is T, then its corresponding level value is V=T×D; finally, V is displayed with the required number of vertical scales.

[0028] The object of the invention of the present invention is achieved in this way:

[0029] The present invention provides a channel gain calibration and display method capable of changing the vertical scale number, which converts the quantization range of ADC (2 N , N = number of ADC bits), after removing the highest and lowest values ​​(closer to the upper and lower edges, the greater the error), the entire quantization value range is divided into M (M is a multiple of 2) segments, with 2 N / 2 is the center (which is equivalent to the 0 level of the AC signal), so that the amplitude value of the calibration signal after quantization falls at the set position. The channel gain control word obtained at this time is the calibration data to be obtained. Finally, the level scale and the corresponding level value of the quantization value of each ADC in each amplitude level are calculated and displayed with the required number of vertical scales.

[0030] At the same time, the channel gain calibration and display method with changeable vertical scale number of the present invention also has the following beneficial effects:

[0031] (1) The vertical display scale can be adjusted automatically or by the user according to the amplitude of the signal to be measured to achieve the best vertical area viewing ratio.

[0032] (2) Calibration should be related to the design and manufacture of the hardware and has nothing to do with the display mode. Different display modes have only one set of calibration data;

[0033] (3) The display conversion formula based on the ADC sampling quantization data is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a comparison chart of vertical area visual ratio of different display modes;

[0035] Figure 2 It is a flow chart of a channel gain calibration and display method with changeable vertical scale number according to the present invention; DETAILED DESCRIPTION

[0036] The specific implementation of the present invention is described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0037] Example

[0038] Figure 2 The invention discloses a flow chart of a channel gain calibration and display method capable of changing the vertical scale number.

[0039] In this embodiment, if Figure 1 As shown, the present invention provides a channel gain calibration and display method with changeable vertical scale number, comprising the following steps:

[0040] S1, segmenting the quantized value of ADC;

[0041] Assume that the given quantization value range of ADC is 0 to 2 N -1, set the minimum value of the changeable vertical scale number to M;

[0042] According to the performance of the ADC and the performance of the analog channel, the highest and lowest values ​​of the ADC quantization value are removed, and 80% of the given quantization value range is retained, which is recorded as the applicable quantization range N;

[0043] Divide the applicable quantization range N into M segments, each segment contains m quantization words, m = N ÷ M, and m is an integer;

[0044] In this embodiment, taking an 8-bit ADC as an example, the quantization value range is 0 to 2 N -1, i.e. 0 to 255, remove the high end (>228) of the quantization value of ADC and remove the bottom end (<28), and get the applicable range (28 to 228, 200 quantization words). Divide this quantization range into 8 segments, each with 25 (m) quantization words.

[0045] S2. Setting calibration criteria;

[0046] The calibration criterion is that the amplitude of the calibration signal occupies K segments out of M segments, that is, the amplitude of the calibration signal occupies K×m quantization words, K <M;

[0047] In this embodiment, the amplitude of the calibration signal occupies 6 (K) segments of the 8 (M) segments as the calibration criterion, that is, the amplitude of the calibration signal occupies 6×25=150 quantization words.

[0048] S3, determining the amplitude of each amplitude level calibration signal;

[0049] Assume that the current amplitude position to be calibrated is R, and the unit is V / DIV; then the amplitude value of the calibration signal output by the calibrator is K×R, and the unit is V;

[0050] In this embodiment, the amplitude of the calibration signal is 6 (K) grid signals of the amplitude level. Taking the calibration of the 200mV (R) level as an example, the calibration signal is set to have an amplitude of 6 grids, that is, 200mV×6=1.2V.

[0051] Combined with the setting of S1, the 1.2V signal occupies 6 segments in the ADC quantization segment, that is, 150 quantization words. Then, at this gear, the signal represented by each quantization word is 150 bits / 1.2V=0.125 bits / mV.

[0052] S4. Calibration

[0053] The calibrator outputs the calibration signal to the analog channel, and then samples the calibration signal through the ADC, and then calculates the current gain value. If the gain value is equal to K×m=150 quantization words, it indicates that the gear calibration is completed; otherwise, adjust the gain control word of the channel, and then resample and calculate the gain value through the ADC until the gain value is equal to K×m=150 quantization words, and the gear calibration is completed;

[0054] Calibrate each amplitude level in turn until all amplitude levels are calibrated;

[0055] S5. Waveform display when vertical scale number changes

[0056] After the calibration in step S4, the level scale D corresponding to the quantized value of each ADC in each amplitude range is calculated, where D=R÷m;

[0057] Assume that a certain quantization value in the actual sampling of the ADC is T, then its corresponding level value is V=T×D; finally, V is displayed with the required number of vertical scales.

[0058] In this embodiment, the calibrated channel gain satisfies: 6×amplitude level=150 ADC quantization words

[0059] The level scale D = R ÷ m corresponding to the quantized value of each ADC in each amplitude range. This value is only related to the amplitude range, not to other values, and is fixed.

[0060] It can be automatically calculated based on the current amplitude level. For example:

[0061]

[0062] When displaying, the collected waveform data (that is, the quantized value of the ADC) is multiplied by D to obtain the absolute quantized value of the current waveform in mV, and then displayed in the required display mode.

[0063] For example, if the 8DIV mode is used, each DIV occupies 100 pixels in the waveform display area (the total display area height is 8×100=800 pixels), then 100 pixels in height represent the voltage of 1DIV. For example, in the 20mV range, one grid is 20mV, and the occupied display pixels are 100. If the 10DIV mode is used, in the same display area, each DIV occupies 80 display pixels (=800 / 10), then 80 pixels represent 20mV.

[0064] For example, for a 160mV signal, in 8DIV mode, the display will be close (the noise part exceeding 160mV will not be displayed). At this time, 10DIV mode is used, and the waveform only occupies 8DIV, so the entire waveform can be fully observed.

[0065] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A channel gain calibration and display method with variable vertical scale number, characterized in that: The following steps are involved: (1) Segment the ADC quantization value; Assume that the given quantization value range of ADC is 0 to 2 N -1, set the minimum value of the changeable vertical scale number to M; According to the performance of the ADC and the performance of the analog channel, the highest and lowest values ​​of the ADC quantization value are removed, and 80% of the given quantization value range is retained, which is recorded as the applicable quantization range N; Divide the applicable quantization range N into M segments, each segment contains m quantization words, m = N ÷ M, and m is an integer; (2) Setting calibration criteria; The calibration criterion is that the amplitude of the calibration signal occupies K segments out of M segments, that is, the amplitude of the calibration signal occupies K×m quantization words, K <M; (3) Determine the amplitude of the calibration signal of each amplitude gear; Assume that the current amplitude position to be calibrated is R, and the unit is V / DIV; then the amplitude value of the calibration signal output by the calibrator is K×R, and the unit is V; (4) Calibration The calibrator outputs the calibration signal to the analog channel. After the analog channel conditions the signal, it is input to the ADC for sampling. The signal sampled by the ADC is calculated to obtain the gain value of the sampled signal. If the gain value is equal to K×m quantization words, it indicates that the gear calibration is completed; otherwise, the gain control word of the channel is adjusted, and then the ADC is resampled and the gain value is calculated until the gain value is equal to K×m quantization words. The gear calibration is completed; Calibrate each amplitude level in turn until all amplitude levels are calibrated; (5) Waveform display when vertical scale number changes After the calibration in step (4), the level scale D corresponding to the quantized value of each ADC in each amplitude range is calculated, where D = R ÷ m; Assume that a certain quantization value in the actual sampling of the ADC is T, then its corresponding level value is V=T×D; finally, V is displayed with the required number of vertical scales.

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