An adaptive measurement method and system for dynamically adjusting the ADC reference voltage

Abstract

This invention discloses an adaptive measurement method and system for dynamically adjusting the reference voltage of an ADC, used to measure the voltage of a target sample. The method first converts the differential output voltage of the target sample into a single-ended voltage signal via a first-stage operational amplifier and inputs it to the non-inverting input of a second-stage operational amplifier. A dynamically adjustable reference voltage is then connected to the inverting input of the second-stage operational amplifier. Further, the current code value output by the ADC is sampled to determine if it falls within a predetermined range. If not, the reference voltage is dynamically adjusted, and the sampling and determination process is repeated until the ADC output code value falls within the predetermined range. Finally, the precise voltage value of the target sample is calculated based on the code value and the corresponding reference voltage. Thus, this invention achieves wide-range, high-precision adaptive measurement by dynamically adjusting the reference voltage in a closed loop without changing the analog gain, effectively overcoming the error and delay problems introduced by gain switching in traditional solutions.

Description

Technical Field

[0001] This specification relates to one or more embodiments in the field of precision measurement technology, and in particular to an adaptive measurement method and system for dynamically adjusting the ADC reference voltage. Background Technology

[0002] In modern electronic measurement and control systems, converting continuously changing physical quantities (such as temperature, pressure, voltage, and current) into discrete digital signals that can be recognized and processed by computers or digital processors is fundamental for data analysis, status monitoring, and precise control. The analog-to-digital converter (ADC), as the core device for this conversion, directly determines the upper limit of the entire data acquisition system's capabilities. Using an ADC for data acquisition is not only a necessary bridge for interaction between the physical and digital worlds, but also a fundamental way to obtain repeatable, quantifiable, and transmittable measurement results.

[0003] The key performance indicators of an ADC are primarily determined by its range and resolution (accuracy). Range refers to the maximum and minimum range of input analog voltages that the ADC can measure (e.g., ±2.5V, 0~5V), and is an inherent hardware attribute of the ADC. Resolution refers to the smallest voltage change that the ADC can distinguish, usually expressed in bits (e.g., 16-bit, 24-bit) or the least distinguishable voltage (LSB). For example, for a 16-bit ADC with a 5V range, its LSB is 5V / 2. 16 ≈ 76μV. Resolution essentially describes the fineness of the "scale" of an ADC within a given range. As can be seen from the definition, for a fixed-bit ADC, there is a natural and unavoidable contradiction between its range and resolution: Given a fixed reference voltage, the wider the range, the larger the absolute voltage value represented by each quantization step (LSB), and the lower the resolution for minute signals; conversely, if extremely high resolution is desired, the range must be limited, otherwise the required number of bits in the ADC will increase dramatically, even to the point of being impractical or uneconomical in engineering. This contradiction is a fundamental limitation determined by the quantization principle and hardware structure of the ADC.

[0004] However, many cutting-edge scientific research and industrial testing scenarios demand that measurement systems maintain extremely high accuracy in capturing minute changes within a wide input range while covering a large input range. A typical example is the K-coefficient calibration of semiconductor power devices. In this process, the device needs to be tested over a wide temperature range (e.g., 20°C to 180°C), with its terminal voltage varying across hundreds of millivolts with temperature. To accurately calibrate the voltage change corresponding to a temperature change (e.g., 0.1°C), i.e., the K-coefficient, the ADC needs to have microvolt-level resolution. This means that the data acquisition system must be able to accommodate a wide voltage swing of hundreds of millivolts without saturation, while maintaining microvolt-level measurement resolution across this entire range.

[0005] Therefore, faced with the inherent contradiction between range and accuracy determined by the hardware nature of ADCs, and the ever-increasing demand for high-standard measurements, the field urgently needs an innovative technical solution that can achieve a balance between wide input range and high measurement accuracy without significantly increasing system complexity or introducing additional error sources. This would provide a better technical solution for the field of precision measurement, especially for high-requirement applications such as K-coefficient calibration. Summary of the Invention

[0006] This specification describes an adaptive measurement method and system for dynamically adjusting the ADC reference voltage, which can solve the above-mentioned technical problems.

[0007] According to a first aspect, an adaptive measurement method for dynamically adjusting an ADC reference voltage is provided for measuring the voltage of a target sample. The differential output voltage of the target sample is input to a first-stage operational amplifier to convert it into a single-ended voltage signal; the single-ended voltage signal is applied to the non-inverting input of a second-stage operational amplifier, and a reference voltage is applied to the corresponding inverting input; the second-stage operational amplifier is configured to subtract the signals from the non-inverting and inverting inputs, and its output is connected to the analog signal input of the ADC. This adaptive measurement method includes:

[0008] The sampling and judgment process involves sampling the current code value at the digital output of the ADC and determining whether it falls within a predetermined interval. This predetermined interval is either the digital code range of the ADC or a sub-interval of that range. If the determination fails, the reference voltage is adjusted, and the sampling and judgment process continues iteratively until the sampled current code value falls within the predetermined interval. Based on the current code value falling within the predetermined interval and the corresponding reference voltage, the final voltage value of the target sample is determined.

[0009] Furthermore, in one embodiment, the reference voltage is generated using a DAC.

[0010] In one embodiment, the sub-interval corresponds to the remaining portion after removing 10% of the edge portions at each end from the digital code range interval.

[0011] In one embodiment, adjusting the value of the reference voltage if no is determined includes: increasing the reference voltage if it is determined that the sampled code value is greater than the upper limit of the predetermined interval.

[0012] In one embodiment, adjusting the value of the reference voltage when it is determined that no, includes: reducing the reference voltage when it is determined that the sampled code value is less than the lower limit of the predetermined interval.

[0013] In one embodiment, determining the final voltage value of the target sample based on the current code value falling within the predetermined interval and the corresponding reference voltage includes: calculating the product between the ratio of the current code value to the full-scale digital code of the ADC and the nominal voltage range of the ADC; and calculating the sum of the product and the reference voltage as the final voltage value.

[0014] In one embodiment, the target sample is a semiconductor device, and the final voltage value is used to calibrate the K coefficient of the semiconductor device.

[0015] According to a second aspect, an adaptive measurement system for dynamically adjusting an ADC reference voltage is provided for measuring the voltage of a target sample, characterized in that the adaptive measurement system comprises:

[0016] The first-stage operational amplifier is configured to convert the differential output voltage of the target sample into a single-ended voltage signal. The second-stage operational amplifier is configured to subtract the single-ended voltage signal input through its non-inverting input from a reference voltage input through its inverting input. The ADC is configured to use the output of the second-stage operational amplifier as its input. The controller includes the following functional modules: a sampling judgment module, configured to sample the code value currently output by the digital output terminal of the ADC and determine whether the code value falls within a predetermined interval, where the predetermined interval is the digital code range interval of the ADC, or a sub-interval of the digital code range interval; a reference voltage adjustment module, configured to adjust the value of the reference voltage if the determination is negative; an iteration start module, configured to start the next sampling judgment, and so on iteratively until the sampled code value falls within the predetermined interval; and a voltage value determination module, configured to determine the final voltage value of the target sample based on the current code value falling within the predetermined interval and the corresponding reference voltage.

[0017] In one embodiment, the reference voltage adjustment module is specifically configured to: increase the reference voltage when it is determined that the sampled code value is greater than the upper limit of the predetermined interval; or, decrease the reference voltage when it is determined that the sampled code value is less than the lower limit of the predetermined interval.

[0018] In one embodiment, the reference voltage adjustment module is specifically configured to adjust the reference voltage generated by the DAC by writing a new digital code value into the DAC.

[0019] In summary, by using the methods and systems disclosed in the embodiments of this specification, the reference voltage of the ADC itself can be dynamically and in a closed loop adjusted, thereby achieving adaptive expansion of the measurement range while maintaining the original high resolution of the ADC. This overcomes the disadvantages of traditional PGA solutions, such as the introduction of additional errors, switching delays, and high costs. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The diagram illustrates the relationship between temperature and voltage changes over a wide range during K-coefficient calibration.

[0022] Figure 2 Indication Figure 1 The regions S1 and S2 that cannot be directly measured in the middle;

[0023] Figure 3 This is a schematic diagram of the functional structure of the measurement system in the improved solution proposed in this invention;

[0024] Figure 4 Indication Figure 3 The flow steps of the test logic executed by the controller 350;

[0025] Figure 5 This diagram illustrates the effect of full-range continuous data acquisition that can be achieved using the improved solution proposed in this invention.

[0026] Figure 6 For the purpose Figure 3 A schematic diagram of the functional modules included in the controller 350. Detailed Implementation

[0027] The solution provided in this specification will now be described with reference to the accompanying drawings.

[0028] As mentioned earlier, the inherent contradiction between range and accuracy in ADC hardware is becoming increasingly prominent, while the demand for high-standard measurements of wide dynamic range and weak signals continues to grow. However, there is currently no technical solution that can effectively unify wide input range and high measurement accuracy without significantly increasing system complexity or introducing additional error sources.

[0029] Specifically, see Figure 1 In industrial applications, to accurately measure the K-coefficient of a sample, a sufficiently large temperature range is required: from T1 to T2. This large temperature range leads to a significant voltage variation at the sample terminals: from V1 to V2. However, for high-precision voltage acquisition circuits, higher precision results in a smaller measurement range. Therefore, during testing, the voltage is often only measured up to V. R1 To V R2 This part.

[0030] See Figure 2 For areas S1 and S2 that cannot be directly and accurately measured, they cannot be used because their changing trends and safety cannot be accurately assessed.

[0031] To address the aforementioned issues, conventional technical solutions typically employ an extended voltage measurement range to cover the entire variation range of the signal under test. A typical system using this approach consists of an analog-to-digital converter (ADC) with a fixed reference voltage and a pre-amplifier (PGA). The microcontroller unit (MCU) determines the PGA gain based on the initial amplitude acquisition: if the amplitude is too small, the MCU increases the PGA gain; if the amplitude is too large, approaching saturation, the MCU decreases the PGA gain. By switching between different gain levels, the amplitude of the input signal is adjusted to the optimal operating range of the ADC, thus adapting to signals of varying amplitudes and achieving the corresponding effective resolution and range.

[0032] However, this conventional approach has the following shortcomings:

[0033] 1) Introducing additional noise and nonlinear errors: PGAs are active analog devices, and their gain switching process introduces additional thermal noise, offset voltage, and gain errors. These errors will be sampled by the subsequent ADC, directly leading to a decrease in the absolute accuracy of the system and affecting its stability under temperature changes.

[0034] 2) Switching Transient and Response Delay: The gain switching to analog mode requires a certain settling time. At the moment of switching, the PGA output is unstable, rendering the sampled data during that period invalid. This not only reduces the overall measurement speed but may also cause the loss of critical data when monitoring continuously and rapidly changing signals.

[0035] 3) Increased system complexity and cost: Implementing this solution requires additional high-performance, multi-stage PGA chips and sophisticated analog multiplexers, which significantly increases circuit complexity, system design difficulty, and overall hardware cost.

[0036] 4) Complex control logic: In order to avoid frequent gain oscillations near the switching threshold, the switching threshold needs to be set precisely and a hysteresis control mechanism needs to be introduced, which further increases the complexity of software algorithm design and implementation.

[0037] Based on the above observations and analysis, this specification proposes an improved scheme, the core principle of which is: the controller dynamically generates and applies a suitable reference voltage V based on the sampling output of the ADC. ref This is supplied to the second-stage operational amplifier. V ref The change is equivalent to superimposing an opposite bias voltage on the input signal, thereby "shifting" the signal under test to the center region of the ADC range.

[0038] In this way, without the need for front-end analog gain switching, the ADC’s ​​own reference voltage is dynamically and in a closed loop adjusted, thereby achieving adaptive expansion of the measurement range while maintaining the original high resolution of the ADC. This overcomes the disadvantages of the PGA solution, such as the introduction of additional errors, switching delays, and high costs.

[0039] The following section introduces the functional structure of the measurement system in the improved solution, as well as the logical flow of testing (or measurement).

[0040] See Figure 3 The measurement system includes a first-stage operational amplifier 310, a second-stage operational amplifier 320, a dynamic reference voltage source 330, an ADC 340, and a controller 350, wherein:

[0041] The input of the first-stage operational amplifier 310 is connected to the target sample under test, and is used to convert the differential output voltage of the target sample into a single-ended voltage signal (a voltage signal referenced to the system common reference ground). It should be understood that the gain of the first-stage operational amplifier 310 can be set to 1. In this case, the values ​​of the differential output voltage and the single-ended voltage signal are equal, and both correspond to the final voltage value V that needs to be determined. in (or written as V) fFurthermore, the specific connection method between the first-stage operational amplifier 310 and the target sample can be implemented using relevant existing technologies, which is not the focus of this solution and will not be elaborated here.

[0042] The non-inverting input of the second-stage operational amplifier 320 is connected to the output of the first-stage operational amplifier 310, and the inverting input is connected to the dynamic reference voltage source. The second-stage operational amplifier 320 is configured to output a single-ended voltage signal from the first-stage operational amplifier 310 and a reference voltage V generated by the dynamic reference voltage source 330. ref Perform a subtraction operation to obtain the voltage difference V from the subtraction operation. d Direct output (gain of 1).

[0043] The dynamic reference voltage source 330 can generate a dynamically changing voltage, which is used as the reference voltage for the second-stage operational amplifier 320. Exemplarily, the dynamic reference voltage source 330 can be implemented as a digital-to-analog converter (DAC), allowing different digital code values ​​to be written into it by the controller 350 to achieve control over the reference voltage V. ref Dynamic adjustments.

[0044] The analog input terminal of ADC340 is electrically connected to the output terminal of the second-stage operational amplifier 320. It is used to receive the voltage difference signal output by the second-stage operational amplifier 320, and to perform sampling and quantization operations on the voltage difference signal to convert it into the corresponding digital code value.

[0045] The controller 350, connected to both the dynamic reference voltage source 330 and the digital output of the ADC 340, is configured to execute test logic to dynamically and in a closed-loop manner adjust the reference voltage of the ADC 340. This allows for adaptive expansion of the measurement range while maintaining the original high resolution of the ADC 340, ultimately calculating the high-precision voltage value V of the target sample. in For example, the controller 350 can be implemented as a microcontroller (MCU), or a field-programmable gate array (FPGA), etc.

[0046] It should be noted that the gains of the first-stage operational amplifier 310 and the second-stage operational amplifier 320 can also be different from 1, but they are fixed and do not need to be adjusted during the measurement of the same sample. For the sake of brevity, this article mainly uses the example of both operational amplifiers having a gain of 1.

[0047] Next, we will describe the test logic executed in the controller. See [link / reference] Figure 4 The test logic can be broken down into the following steps:

[0048] 1. Initialization: When the test system is powered on or a new measurement begins, the controller 350 will set the reference voltage V. ref Set to a preset initial value V0 (e.g., 0 volts).

[0049] 2. Acquisition and Judgment (or Sampling Judgment): The controller initiates a high-precision sampling of the ADC to obtain the current code value output by the ADC, or the original digital code value D. raw The controller determines D. raw Whether it is within the predetermined range is denoted as [D] L D H ].

[0050] In one embodiment, the predetermined interval can be the digital code range interval of the ADC, which corresponds to the full-scale range of the ADC.

[0051] In another embodiment, the predetermined interval can be a sub-interval of the digital code range, which can also be referred to as a safety threshold interval. For example, the safety threshold interval can correspond to 10% to 90% of the ADC range, that is, the remaining portion after removing the 10% edge portions at each end of the digital code range. This safety threshold interval setting avoids the nonlinear risks that may arise from operating at the range edges.

[0052] 3. Dynamic adjustment (closed-loop feedback):

[0053] Case A (Optimal): If D raw In [D] L D H [Insert text here] indicates the current reference voltage V. ref If the settings are appropriate, the sampled signal will fall exactly within the reasonable range of the ADC (i.e., the predetermined range). In this case, you can directly proceed to step "4. Result Calculation".

[0054] Case B (Exceeding the upper limit): If D raw > D H This indicates that the signal sampled by the ADC is too large, even with the current V. ref The bias is still close to the positive saturation of the ADC. In this case, the controller can control the V output of the dynamic reference voltage source (e.g., command DAC). ref Increase a step size ΔV, based on V d =V in -V ref It can be seen that V ref After the addition, the signal D sampled by the ADC raw (Positively correlated with V) d The signal then decreases, thus shifting the signal to or closer to the predetermined range.

[0055] Case C (beyond the lower limit): If D raw < D L This indicates that the signal sampled by the ADC is too small, even if the current V... ref The bias remains close to ADC negative saturation (ADC bipolar) or zero-scale saturation (ADC unipolar). In this case, the controller can control the V output of the dynamic reference voltage source (e.g., command DAC). ref Decrease by one step size ΔV, based on V d =V in -V ref It can be seen that V ref After reduction, the signal D sampled by the ADC raw (Positively correlated with V) d The signal then rises, thus shifting the signal to or closer to the predetermined range.

[0056] It should be understood that the step size ΔV for increasing or decreasing can be set by staff based on practical experience. For example, it can be set to a fixed value for each adjustment, or it can be set as a step value, etc.

[0057] Adjust V in case B or C ref Then, return to step "2, Sampling and Judgment" to perform the next sampling and judgment. This process iterates rapidly and usually converges within 1-3 iterations.

[0058] 4. Result Calculation: After the acquired code value stabilizes within the predetermined range, calculate the final voltage value V. f (corresponding to the aforementioned V) in The calculation formula is:

[0059] V f = (D raw / D Full *Range + V ref (1)

[0060] Among them, D raw For the sampled code value falling within the predetermined interval, D Full This is the full-scale digital code for the ADC, where Range is the ADC's nominal voltage range (e.g., 5V). ref This is the reference voltage. The formula combines the ADC reading with compensation for reference voltage offset.

[0061] It should be understood that formula (1) corresponds to the case where the gain of both the first-stage operational amplifier and the second-stage operational amplifier is 1. A more general formula can be used as follows:

[0062] V f =[ (D raw / D Full) *(Range / β)+ V ref ] / α (2)

[0063] Where α represents the gain of the first-stage operational amplifier and β represents the gain of the second-stage operational amplifier.

[0064] 5. Output Results: The final output can be a high-precision V value. f .

[0065] The above logic control flow enables continuous data acquisition across the entire measurement range, and the final result is as follows: Figure 5 As shown, compared to Figure 2 It can achieve accurate measurement of areas S1 and S2 that were originally impossible to measure directly and accurately.

[0066] Furthermore, according to another embodiment, the control logic in the controller 350 can employ... Figure 6 The following functional modules are shown in the figure to implement this:

[0067] The sampling and judgment module 61 is configured to sample the code value currently output by the digital output terminal of the ADC and determine whether the code value falls within a predetermined interval, wherein the predetermined interval is the digital code range interval of the ADC, or a sub-interval of the digital code range interval.

[0068] The reference voltage adjustment module 63 is configured to adjust the value of the reference voltage if a no-determination condition is found.

[0069] The iteration start module 65 is configured to start the next sampling judgment, and so on, until it is determined that the sampled code value falls within the predetermined interval.

[0070] The voltage value determination module 67 is configured to determine the final voltage value of the target sample based on the code value falling within the predetermined interval, the reference voltage, and the predetermined interval.

[0071] It should be noted that for a description of the above functional modules, please refer to the relevant description of the process steps in the foregoing embodiments, which will not be repeated here.

[0072] In summary, the improved solution proposed in this specification can achieve the following technical effects:

[0073] 1) Maintain optimal accuracy: By avoiding analog gain switching, the system only uses the sampling link of the ADC itself, which preserves the original performance indicators of the ADC (noise, linearity, temperature drift) to the greatest extent, resulting in higher measurement accuracy.

[0074] 2) Achieve seamless range shift: The adjustment of the reference voltage is dynamic, especially through digital control via DAC, which has fast switching speed and no analog transients, and can achieve near-seamless range "sliding", which is suitable for continuous measurement.

[0075] 3) Extended effective dynamic range: Theoretically, the effective measurement range can be extended to the fixed range of the ADC plus the adjustable range of the reference voltage. For example, if the ADC range is ±2.5V and the adjustable range of the reference voltage is ±5V, then the effective input range of the system can reach ±7.5V, while always maintaining the highest resolution of the ADC for signals within ±2.5V.

[0076] 4) Simplified system and reduced cost: Usually only one high-precision DAC is needed to provide an adjustable reference. Compared with high-performance multi-level PGA solutions, the hardware structure is simpler and the cost may be lower.

[0077] 5) Fully automatic and intelligent: Based on real-time judgment and feedback control of the collected results, it realizes fully automatic adaptive measurement without manual intervention.

[0078] Those skilled in the art will recognize that, in one or more of the examples above, the functions described in this invention can be implemented using hardware, software, firmware, or any combination thereof. When implemented in software, these functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium.

[0079] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of the present invention should be included within the scope of protection of the present invention.

Claims

1. An adaptive measurement method for dynamically adjusting the ADC reference voltage, used to measure the voltage of a target sample, characterized in that: The differential output voltage of the target sample is input to the first-stage operational amplifier to be converted into a single-ended voltage signal; the single-ended voltage signal is applied to the non-inverting input of the second-stage operational amplifier, and a reference voltage is applied to the inverting input corresponding to the non-inverting input; the second-stage operational amplifier is configured to perform a subtraction operation on the signals at the non-inverting input and the inverting input, and its output is connected to the analog signal input of the ADC; The adaptive measurement method includes: Perform sampling judgment: sample the current code value of the digital output terminal of the ADC and determine whether the current code value falls within a predetermined interval, wherein the predetermined interval is the digital code range interval of the ADC, or a sub-interval of the digital code range interval; If the result is negative, the value of the reference voltage is adjusted, and the next sampling judgment is performed. This process is repeated until the current code value of the sampled value is determined to fall within the predetermined range. Based on the current code value falling within the predetermined interval and the corresponding reference voltage, the final voltage value of the target sample is determined.

2. The method according to claim 1, characterized in that, The reference voltage is generated using a DAC.

3. The method according to claim 1, characterized in that, The sub-interval corresponds to the remaining portion after removing 10% of the edge portions at each end from the digital code range interval.

4. The method according to claim 1, characterized in that, If the determination is no, adjust the value of the reference voltage, including: If it is determined that the sampled code value is greater than the upper limit of the predetermined interval, the reference voltage is increased.

5. The method according to claim 1, characterized in that, If the determination is no, adjust the value of the reference voltage, including: If it is determined that the sampled code value is less than the lower limit of the predetermined interval, the reference voltage is reduced.

6. The method according to claim 1, characterized in that, Based on the current code value falling within the predetermined interval and the corresponding reference voltage, the final voltage value of the target sample is determined, including: Calculate the product of the ratio between the current code value and the full-scale digital code of the ADC and the nominal voltage range of the ADC; The sum of the product and the reference voltage is calculated as the final voltage value.

7. The method according to claim 1, characterized in that, The target sample is a semiconductor device, and the final voltage value is used to calibrate the K coefficient of the semiconductor device.

8. An adaptive measurement system for dynamically adjusting an ADC reference voltage, used to measure the voltage of a target sample, characterized in that, The adaptive measurement system includes: The first-stage operational amplifier is configured to convert the differential output voltage of the target sample into a single-ended voltage signal. The second-stage operational amplifier is configured to perform a subtraction operation on the single-ended voltage signal input through its non-inverting input terminal and the reference voltage input through its inverting input terminal. The ADC is configured to take the output of the second-stage operational amplifier as its input. The controller includes the following functional modules: The sampling and judgment module is configured to sample the code value currently output by the digital output terminal of the ADC and determine whether the code value falls within a predetermined interval, wherein the predetermined interval is the digital code range interval of the ADC, or a sub-interval of the digital code range interval. The reference voltage adjustment module is configured to adjust the value of the reference voltage if a no-determination condition is found. The iterative startup module is configured to start the next sampling judgment, and so on, until it is determined that the sampled code value falls within the predetermined interval; The voltage value determination module is configured to determine the final voltage value of the target sample based on the current code value falling within the predetermined interval and the corresponding reference voltage.

9. The adaptive measurement system according to claim 8, characterized in that, The reference voltage adjustment module is specifically configured as follows: If it is determined that the sampled code value is greater than the upper limit of the predetermined interval, the reference voltage is increased; or, if it is determined that the sampled code value is less than the lower limit of the predetermined interval, the reference voltage is decreased.

10. The adaptive measurement system according to claim 8, characterized in that, The reference voltage adjustment module is specifically configured as follows: The reference voltage generated by the DAC is adjusted by writing new digital code values ​​into the DAC.

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