A fast temperature compensation method for oscilloscope amplitude calibration

Abstract

The present invention discloses a fast temperature compensation method for oscilloscope amplitude calibration. The method changes the ambient temperature value and automatically records the amplitude change of the signal at different amplitude gears of the oscilloscope caused by the ambient temperature change. Then, the least square method and normalization are used to perform curve fitting and amplitude calibration on the obtained data to generate corresponding temperature compensation curves and temperature compensation coefficients. In this way, the degree of influence of the ambient temperature change on each amplitude gear under different analog channels of the oscilloscope is obtained. Finally, the corresponding temperature compensation coefficient is issued according to the ambient temperature value obtained in real time. This method can quickly alleviate the problem of displayed waveform amplitude deviation caused by the ambient temperature change. At the same time, it also makes up for the vacancy of the focus of the existing amplitude compensation scheme. The method has the characteristics of fast amplitude compensation and has a relatively good compensation effect.

Description

Technical Field

[0001] The invention belongs to the technical field of oscilloscopes, and more particularly relates to a fast temperature compensation method for oscilloscope amplitude calibration. Background Art

[0002] The rapid advancement of modern technology has fueled the rapid development of the electronics industry. Oscilloscopes, one of the most fundamental measuring instruments in the electronics field, are also steadily advancing toward higher sampling rates and higher resolutions. However, as oscilloscope measurement accuracy continues to improve, the impact of various environmental instabilities has become increasingly significant.

[0003] Temperature, one of the most common interference factors, significantly impacts the amplitude accuracy of signals entering an oscilloscope. A typical digital oscilloscope primarily consists of analog channels, as well as acquisition, processing, and display modules. Analog signals entering the oscilloscope first pass through the analog channels, where their amplitude, offset, and other parameters are regulated to within the input range of the subsequent analog-to-digital converter. However, because the front-end analog channels are composed of various temperature-sensitive electronic components, even slight temperature differences can cause the signal passing through the analog channels to deviate significantly from the expected ideal signal. These multiple errors accumulate and can result in significant errors in the signal amplitude acquired, processed, and displayed by the subsequent stages.

[0004] Existing amplitude compensation solutions for oscilloscope input signals often focus on amplitude deviations caused by insufficient bandwidth and frequency response optimization, with little attention paid to amplitude deviations caused by ambient temperature changes. However, for high-precision digital oscilloscopes, amplitude deviations caused by ambient temperature changes are a real problem. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a fast temperature compensation method for oscilloscope amplitude calibration, which supplements the ambient temperature by a temperature compensation coefficient, thereby overcoming the significant interference caused by changes in ambient temperature on the amplitude of the input oscilloscope signal.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a rapid temperature compensation method for oscilloscope amplitude calibration, characterized by comprising the following steps:

[0007] (1) Set the constant temperature and humidity test chamber to an initial ambient temperature value T N ℃;

[0008] (2) Place the oscilloscope to be tested in the test chamber and connect the cables and power supply. Wait for the channel temperature of the oscilloscope to stabilize and maintain at T k ℃ or so;

[0009] (3) Control the oscilloscope calibrator to input a standard square wave signal to any amplitude level of channel I of the oscilloscope to be tested, and the input standard square wave signal makes the signal displayed on the oscilloscope to be tested occupy all six grids;

[0010] (4) Without changing the amplitude and frequency of the standard square wave signal, adjust the ambient temperature to T N ℃, adjust the temperature up and down in equal intervals, and then record the channel temperature value of the oscilloscope under test and the amplitude of the displayed signal at each temperature;

[0011] (5) According to the temperature and amplitude recorded in step (4), a fitting curve of amplitude variation with temperature is fitted by the least squares method;

[0012] (6) Normalize the fitting curve: take the channel temperature T k ℃ is the reference value, at T k When the oscilloscope is at ℃, the amplitude of the signal displayed is A k , then multiply each ordinate value on the fitting curve by 1 / A k , thus completing the normalization process;

[0013] (7) Take the reciprocal of all ordinate values ​​on the normalized fitting curve and then connect them in sequence to obtain the temperature compensation curve;

[0014] (8) Amplitude calibration: Set the calibration temperature value T p ℃, use the oscilloscope calibrator and the automatic amplitude calibration function of the oscilloscope to complete the amplitude calibration under the current channel and amplitude range;

[0015] (9) Calculate the temperature compensation curve after amplitude calibration: take the calibration temperature T p ℃ is the reference value, at T p When the oscilloscope is at ℃, the amplitude of the signal displayed is A p , then divide each vertical coordinate value on the temperature compensation curve by A k / A p , thus obtaining the temperature compensation curve after amplitude calibration;

[0016] (10) Performing temperature sampling at equal intervals on the temperature compensation curve after amplitude calibration, and the obtained ordinate value is used as the temperature compensation coefficient at the corresponding temperature;

[0017] (11) Repeat steps (3) to (10) to generate temperature compensation coefficients for different channels and amplitude levels of the oscilloscope to be tested;

[0018] (12) The system platform writes the temperature compensation coefficient into the oscilloscope to be tested. The oscilloscope to be tested automatically turns on the temperature compensation function during real-time operation and automatically issues the corresponding temperature compensation coefficient based on the temperature value transmitted back by the channel in real time.

[0019] The object of the invention of the present invention is achieved like this:

[0020] The present invention discloses a rapid temperature compensation method for oscilloscope amplitude calibration. The method changes the ambient temperature value and automatically records the amplitude change of the signal at different amplitude gears of the oscilloscope caused by the ambient temperature change. The method then uses the least square method and normalization to perform curve fitting, amplitude calibration and other processing on the obtained data to generate corresponding temperature compensation curves and temperature compensation coefficients, thereby obtaining the degree of influence of the ambient temperature change on each amplitude gear under different analog channels of the oscilloscope. Finally, the corresponding temperature compensation coefficient is issued according to the ambient temperature value obtained in real time. The problem of displayed waveform amplitude deviation caused by the ambient temperature change can be quickly alleviated. At the same time, the method also makes up for the lack of focus of existing amplitude compensation solutions, has the characteristics of rapid amplitude compensation, and has a relatively good compensation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the temperature test platform architecture diagram;

[0022] Figure 2 This is a schematic diagram of a fast temperature compensation method for oscilloscope amplitude calibration according to the present invention;

[0023] Figure 3 is the fitting curve of amplitude-channel temperature;

[0024] Figure 4 is the amplitude-channel temperature normalized curve;

[0025] Figure 5 is the normalized temperature compensation curve;

[0026] Figure 6 is the normalized temperature compensation curve after amplitude calibration;

[0027] Figure 7 is the temperature compensation coefficient curve;

[0028] Figure 8 is the amplitude-channel temperature fitting curve in the example;

[0029] Figure 9 is the normalized curve of amplitude-channel temperature in the example;

[0030] Figure 10 is the normalized temperature compensation curve in the example;

[0031] Figure 11is the normalized temperature compensation curve after amplitude calibration in the example; DETAILED DESCRIPTION

[0032] The following describes the specific embodiments of the present invention 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 detailed descriptions of known functions and designs may dilute the main content of the present invention, such descriptions will be omitted here.

[0033] Example

[0034] In this embodiment, if Figure 1 As shown in the figure, the temperature test platform mainly involves three parts of instruments: constant temperature and humidity test chamber, oscilloscope calibrator, and digital oscilloscope.

[0035] Constant temperature and humidity test chamber: The main function of a constant temperature and humidity test chamber is to create special ambient temperature conditions for oscilloscope temperature testing. This temperature test is expected to be conducted within a temperature range of -10°C to +40°C, so this requirement should be used as the basis for selection when selecting a constant temperature and humidity test chamber. For example, the PDL-800 constant temperature and humidity test chamber was selected as the test machine. Its adjustable temperature range is -40°C to +150°C (the main unit and dehumidifier must be separated when the temperature exceeds 100°C), the temperature deviation is less than 0.5°C, the heating rate is 1 to 3°C / min, and the cooling rate is 0.7 to 1°C / min. The ambient temperature indicators it can provide basically meet the expected temperature test requirements.

[0036] Oscilloscope calibrator: Used to generate square wave signals with standard amplitude. It outputs a series of amplitude reference signals Aci (i represents the amplitude level sequence) to each amplitude level of each channel of the oscilloscope at different ambient temperatures.

[0037] Digital oscilloscope: As the instrument being tested, the oscilloscope will detect the analog channel temperature in the chassis, which mainly includes the overall average temperature of various components involved in the analog signal conditioning process; on the other hand, it will display the amplitude of the input signal.

[0038] In this embodiment, if Figure 2 As shown in the figure, the influence of different temperatures on the amplitude of the input oscilloscope signal is tested. The specific process is as follows:

[0039] (1) Set the constant temperature and humidity test chamber to an initial ambient temperature value T N ℃;

[0040] (2) Place the oscilloscope to be tested in the test chamber and connect the cables and power supply. Keep it for about 30 minutes until the channel temperature of the oscilloscope is stable and remains at T k ℃ or so;

[0041] (3) Control the oscilloscope calibrator to input a standard square wave signal to any amplitude level of channel I of the oscilloscope to be tested, and the input standard square wave signal makes the signal displayed on the oscilloscope to be tested occupy all six grids; in this embodiment, the oscilloscope calibrator outputs a standard square wave signal with a fixed frequency and an amplitude of A. k , the amplitude value can fluctuate appropriately, but it must be ensured that the signal displayed on the oscilloscope to be tested occupies all six grids at the current vertical scale;

[0042] (4) Without changing the amplitude and frequency of the standard square wave signal, adjust the ambient temperature to T N ℃, adjust the temperature up and down in equal intervals, and then record the channel temperature value of the oscilloscope under test and the amplitude of the displayed signal at each temperature;

[0043] In this embodiment, the ambient temperature is changed to T N+1 、T N-1 、T N+2 、T N-2 ...Affected by the change in ambient temperature, the channel temperature also changes to T k+1 、T k-1 、T k+2 、T k-2 Each time the ambient temperature is adjusted up or down in the constant temperature and humidity test chamber, the channel temperature value and the amplitude of the oscilloscope display signal at that ambient temperature are automatically recorded, completing the temperature test process for a single amplitude level of the analog channel. The above process can then be repeated for the remaining amplitude levels and channel temperature tests.

[0044] (5) According to the temperature and amplitude recorded in step (4), a fitting curve of amplitude variation with temperature is fitted by the least squares method, such as Figure 3 As shown;

[0045] (6) Normalize the fitting curve: take the channel temperature T k ℃ is the reference value, at T k When the oscilloscope is at ℃, the amplitude of the signal displayed is A k , then multiply each ordinate value on the fitting curve by 1 / A k , thus completing the normalization process;

[0046] In this embodiment, Figure 3 For example, when the return channel temperature is T k When ℃, the displayed signal amplitude is A k , and then change the ambient temperature to affect the channel temperature. When the channel temperature is T k+1 ℃, the signal amplitude has changed from the previous A kChange to A k+1 If A k As reference standard 1, the corresponding A k+1 You can use A k+1 / A k Similarly, the amplitudes at the other channel temperatures can be represented by A i / A k , A i Indicates the vertical coordinate value corresponding to different channel temperatures, i = 1, 2, 3, 4... At this time, the horizontal coordinate of the curve is the channel temperature value, and the vertical coordinate is the ratio of the amplitude corresponding to each channel temperature to the corresponding amplitude at the normalized temperature, thus obtaining Figure 4 The normalized fitting curve is shown.

[0047] (7) If you want to alleviate the amplitude error caused by temperature changes, the method is to make the displayed amplitude at different channel temperatures as close as possible to the amplitude at the normalized temperature. Corresponding to the normalized fitting curve, since all the values ​​on it are normalized, all the values ​​that are not 1 on it are as close to 1 as possible. To achieve this goal, take the reciprocal of all the vertical coordinate values ​​on the normalized fitting curve, and then connect them in sequence to obtain Figure 5 The temperature compensation curve shown;

[0048] (8) Figure 5 The value corresponding to the vertical axis in the temperature compensation curve is the temperature compensation coefficient corresponding to different channel temperatures at a specific normalized temperature. Previously, considering that the expansion curve showing the change in amplitude with temperature is an objective and inherent property and has no strong relationship with the selected normalized temperature value, accurate amplitude calibration has not been performed in the previous process. After knowing this feature, we can independently choose to accurately calibrate the input signal amplitude of the oscilloscope under test when it is at an appropriate ambient temperature to ensure that the compensated amplitude is closer to the true value. Therefore, we set an appropriate calibration temperature value T p ℃, use the oscilloscope calibrator and the automatic amplitude calibration function of the oscilloscope to complete the amplitude calibration under the current channel and amplitude range;

[0049] (9) Calculate the temperature compensation curve after amplitude calibration: take the calibration temperature T p ℃ is the reference value, at T p When the oscilloscope is at ℃, the amplitude of the signal displayed is A p , then divide each vertical coordinate value on the temperature compensation curve by A k / A p , thus obtaining the temperature compensation curve after amplitude calibration;

[0050] In this embodiment, if Figure 5As shown, the normalized temperature compensation curve has corresponding ordinate values of A k-1 / A k / A k+1 when the channel temperatures are T k / A k-1 、1、A k / A k+1 respectively. Then, since the amplitude calibration operation is performed at the channel temperature Tp, Tp should be used as the new normalized temperature at this time. Also, because on the original temperature compensation curve, the ordinate value corresponding to the channel temperature Tp is A k / A p . Taking this value as the denominator and the ordinate values corresponding to each channel temperature on the original temperature compensation curve as the numerator, the corresponding ordinate values of the temperature compensation curve after amplitude calibration can be calculated. That is, the ordinate values corresponding to the channel temperatures Tk - 1, Tk, Tp, Tk + 1 (Tk - 1 < Tk < Tp < Tk + 1) on the temperature compensation curve after amplitude calibration can be respectively Thus, Figure 6 the temperature compensation curve after amplitude calibration as shown is obtained;

[0051] (10), As Figure 7 shown, sample the temperature compensation curve after amplitude calibration at intervals of m℃ for the channel temperature, and take the obtained ordinate value as the temperature compensation coefficient at the corresponding temperature. In this embodiment, the temperature compensation coefficient can be stored in the form of a document.

[0052] (11) Repeat steps (3) to (10) to generate the temperature compensation coefficients for different channels and different amplitude ranges of the oscilloscope under test;

[0053] (12) The system platform writes the temperature compensation coefficients into the oscilloscope under test. The oscilloscope under test automatically enables the temperature compensation function during real - time operation and automatically issues the corresponding temperature compensation coefficients according to the temperature values transmitted back by the channel in real time.

[0054] In order to further illustrate the present invention, we analyze and illustrate through specific examples. The digital oscilloscope used in this temperature test has two analog channels with 4G bandwidth and 8G bandwidth, and each channel is further subdivided into different amplitude gears. The amplitude gear of the 8G channel is 10mV / div to 1V / div, and the 4G channel is divided into high-resistance gear and low-resistance gear according to different input impedances. The amplitude gear of the low-resistance gear with 50Ω as input impedance is from 2mV / div to 1V / div, and the amplitude gear of the high-resistance gear with 1MΩ as input impedance is from 2mV / div to 10V / div. Under normal circumstances, amplitude calibration should be performed at each amplitude gear of the two channels mentioned above. However, considering the difficulty in actual experimental operation and the fact that two or more amplitude gears in the same channel will share a set of attenuation gears, etc. When conducting a temperature test, it is only necessary to select a gear from the amplitude gears in the same attenuation gear. Therefore, for the amplitude calibration experiment, select 10mV / div and 50mV / div for an 8G bandwidth channel; 5mV / div, 50mV / div, and 200mV / div for a 4G bandwidth channel in the low impedance range; and 5mV / div, 50mV / div, 200mV / div, and 1V / div for the high impedance range as representative amplitude ranges. The specific implementation of the temperature test will be further explained using the 5mV / div amplitude range in the low impedance range of a 4G bandwidth channel as an example.

[0055] The ambient temperature in the constant temperature and humidity chamber was adjusted to 20°C. A digital oscilloscope was placed in the chamber and preheated for 30 minutes to maintain a stable temperature, ensuring that the temperature transmitted from the oscilloscope's analog channels remained stable. During this time, the relevant control cables were connected. The channel temperature transmitted from the oscilloscope's analog channels remained approximately 29.2°C. Next, while the ambient temperature remained stable, a pre-programmed program fixed the oscilloscope's timebase to 1ms / div and controlled the oscilloscope calibrator to input a standard square wave signal with a frequency of 1kHz and an amplitude of approximately 30mV. The amplitude of the control input signal could fluctuate, but the signal displayed on the oscilloscope occupied all six grids at the current vertical scale. Then, without changing the input waveform amplitude or frequency, we controlled the ambient temperature at 20°C, adjusting it up and down in 5°C increments to 5°C, 10°C, 15°C, 25°C, 30°C, 40°C, and so on, dropping the ambient temperature to a minimum of -10°C and a maximum of 40°C. Each time the ambient temperature was adjusted up or down, the channel temperature value and the amplitude data of the oscilloscope display signal at that ambient temperature were automatically acquired, as shown in Table 1.

[0056]

[0057] Table 1

[0058] After obtaining the channel temperature value and its corresponding amplitude change through temperature test, the relationship curve between amplitude and channel temperature can be fitted based on the measured data, such as Figure 8 As shown. After the fitting is completed, the curve will be normalized. Since the input signal amplitude after rough calibration at a channel temperature of 29.2°C was used as the reference value in the previous temperature test, the current normalized channel temperature is selected as 29.2°C. The amplitude-channel temperature normalization curve is shown as Figure 9 shown.

[0059] After completing the above process, the temperature test process of the 5mV / div amplitude gear under the low resistance gear of the 4G bandwidth channel is realized. If you want to alleviate the amplitude error caused by temperature changes, the method is to make the displayed amplitude at different channel temperatures as close as possible to the amplitude at the normalized temperature. Corresponding to the normalized curve, since all the values ​​on it are normalized, all the values ​​that are not 1 on it are as close to 1 as possible. To achieve this goal, it is necessary to find a suitable temperature compensation curve. If you want to get a temperature compensation curve, just set it: take the inverse of all the vertical coordinate values ​​on the original normalized relationship curve, and then connect them in sequence to get Figure 10 Normalized temperature compensation curve shown.

[0060] The value corresponding to the vertical axis in the above temperature compensation curve is the temperature compensation coefficient corresponding to different channel temperatures when the channel temperature is 29.2℃ as the normalized temperature. Then, the oscilloscope needs to be amplitude calibrated. After the calibration is completed, the program will automatically obtain the current channel temperature value and update the normalized temperature compensation curve based on this data. Assuming that after the amplitude calibration is completed, the channel temperature read is 34.5℃, then the normalized temperature compensation curve after amplitude calibration changes to Figure 11 shown.

[0061] At this point, the temperature compensation curve is obtained after amplitude calibration and normalization. The program then samples the channel temperature of this curve at 0.1°C intervals, generates new temperature compensation coefficients, and automatically saves the sampled values ​​corresponding to the respective channel temperatures in a file. This results in the temperature compensation coefficients after amplitude calibration. Since the oscilloscope system's host computer adjusts signal gain by sending gain control words to the microcontroller on the analog channel board, rapid temperature compensation can be achieved by simply multiplying the gain control words originally sent by the host computer by the corresponding channel temperature compensation coefficient.

[0062] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concepts of the present invention are protected.

Claims

1. A rapid temperature compensation method for oscilloscope amplitude calibration, characterized in that: The following steps are involved: (1) Set the constant temperature and humidity test chamber to an initial ambient temperature value T N ℃; (2) Place the oscilloscope to be tested in the test chamber and connect the cables and power supply. Wait for the channel temperature of the oscilloscope to stabilize and maintain at T k ℃ or so; (3) Control the oscilloscope calibrator to input a standard square wave signal to any amplitude level of channel I of the oscilloscope to be tested, and the input standard square wave signal makes the signal displayed on the oscilloscope to be tested occupy all six grids; (4) Without changing the amplitude and frequency of the standard square wave signal, adjust the ambient temperature to T N ℃, adjust the temperature up and down in equal intervals, and then record the channel temperature value of the oscilloscope under test and the amplitude of the displayed signal at each temperature; (5) According to the temperature and amplitude recorded in step (4), a fitting curve of amplitude variation with temperature is fitted by the least squares method; (6) Normalize the fitting curve: take the channel temperature T k ℃ is the reference value, at T k When the oscilloscope is at ℃, the amplitude of the signal displayed is A k , then multiply each ordinate value on the fitting curve by 1 / A k , thus completing the normalization process; (7) Take the reciprocal of all ordinate values ​​on the normalized fitting curve and then connect them in sequence to obtain the temperature compensation curve; (8) Amplitude calibration: Set the calibration temperature value T p ℃, use the oscilloscope calibrator and the automatic amplitude calibration function of the oscilloscope to complete the amplitude calibration under the current channel and amplitude range; (9) Calculate the temperature compensation curve after amplitude calibration: take the calibration temperature T p ℃ is the reference value, at T p When the oscilloscope is at ℃, the amplitude of the signal displayed is A p , then divide each vertical coordinate value on the temperature compensation curve by A k / A p , thus obtaining the temperature compensation curve after amplitude calibration; (10) Performing temperature sampling at equal intervals on the temperature compensation curve after amplitude calibration, and the obtained ordinate value is used as the temperature compensation coefficient at the corresponding temperature; (11) Repeat steps (3) to (10) to generate temperature compensation coefficients for different channels and amplitude levels of the oscilloscope to be tested; (12) The system platform writes the temperature compensation coefficient into the oscilloscope to be tested. The oscilloscope to be tested automatically turns on the temperature compensation function during real-time operation and automatically issues the corresponding temperature compensation coefficient based on the temperature value transmitted back by the channel in real time.

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