Current measurement system and method for high-frequency electrotome

Abstract

The invention discloses a current measuring system and method for a high-frequency electrotome. The current measuring system comprises a current-to-voltage module, a signal conditioning circuit module, a filter circuit, an MCU and a display module which are connected in sequence. The current-to-voltage module is used for converting the current of the high-frequency electrotome into a corresponding voltage signal; the signal conditioning circuit module firstly performs high-frequency interference filtering on a voltage signal, and performs amplification and direct-current bias on the filtered signal; the filter circuit is used for filtering high-frequency interference from the output end signal of the signal conditioning circuit module to obtain a sampling voltage; the MCU is used for sampling the sampling voltage, calculating the effective value IRMS of the output current, and controlling the size of the direct current bias voltage of the signal conditioning circuit and the control of the amplification factor according to the size of the effective value IRMS; and the display module is used for displaying the measured effective value IRMS. According to the invention, wide-range high-precision current real-time monitoring can be realized, and the measuring result is accurate and reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management systems (BMS), and in particular, to a high-precision current measurement system and measurement method integrated in a BMS Background Art

[0002] As an important medical device widely used in surgical operations, a high-frequency electrosurgical unit cuts and coagulates human tissues by releasing high-frequency current. During the operation, the precise control and real-time monitoring of the output current of the high-frequency electrosurgical unit are crucial for the successful implementation of the operation and the safety of the patient

[0003] Currently, there are many deficiencies in the existing high-frequency electrosurgical unit current measurement technologies. First, the current output by the high-frequency electrosurgical unit has high-frequency characteristics, with its frequency usually between 100 kHz and 5 MHz and containing rich harmonic components. Due to poor frequency response characteristics, traditional current measurement systems are difficult to accurately capture the transient changes of high-frequency current, resulting in large errors in measurement results and unable to provide accurate current information for surgeons, thus affecting the precision of surgical operations. Second, under different surgical modes (such as cutting mode, coagulation mode) of the high-frequency electrosurgical unit, the magnitude and characteristics of its output current will change significantly. The existing current measurement systems have a narrow dynamic range and are difficult to adapt to such wide-range current changes. They may not be able to accurately measure due to insufficient sensitivity during small current measurement, and signal saturation may occur during large current measurement, resulting in measurement failure. Therefore, there is an urgent need for a high-precision and reliable current measurement system that can solve the above problems Summary of the Invention

[0004] The purpose of the present invention is to provide a current measurement system and measurement method for a high-frequency electrosurgical unit. The present invention can achieve real-time monitoring of high-precision current over a wide range, and has the advantages of accurate and reliable measurement results

[0005] The technical solution provided by the present invention is as follows: A current measurement system and measurement method for a high-frequency electrosurgical unit, including a current-to-voltage module, a signal conditioning circuit module, a filtering circuit, an MCU, and a display module connected in sequence; the current-to-voltage module is used to convert the output current of the high-frequency electrosurgical unit into a corresponding voltage signal; the signal conditioning circuit module first filters high-frequency interference from the voltage signal and amplifies and provides a DC bias to the filtered signal; the filtering circuit is used to filter high-frequency interference from the signal at the output end of the signal conditioning circuit module to obtain a sampled voltage; the MCU samples the sampled voltage to calculate the effective value I RMS of the output current, and controls the magnitude of the DC bias voltage and the amplification factor of the signal conditioning circuit according to the magnitude of the effective value I RMS ; the display module is used to display the measured effective value I RMS .

[0006] The above-mentioned current measurement system for a high-frequency electrosurgical unit, wherein the current-to-voltage module consists of a current transformer CT and a resistor R c The input coil of the current transformer CT is used to receive the output current of the high-frequency electrosurgical unit; the resistor R c is connected in parallel across the output coil of the current transformer CT, and one end of the resistor R c is grounded.

[0007] The aforementioned current measurement system for a high-frequency electrosurgical unit, wherein the signal conditioning circuit module includes a capacitor C in_filter , resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, resistor R 10 , NMOS transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, operational amplifier OP1 and operational amplifier OP2; the resistor R1 is connected between the current-to-voltage module and the non-inverting input terminal of the operational amplifier OP1, and C in filter is connected between the non-inverting input terminal of OP1 and the ground; the NMOS transistor Q1 and the resistor R3 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of the operational amplifier OP1, the NMOS transistor Q2 and the resistor R4 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1, the NMOS transistor Q3 and the resistor R5 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1, the NMOS transistor Q4 and the resistor R6 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1; the gates of the NMOS transistors Q1, Q2, Q3 and Q4 are respectively connected to the PA1, PA2, PA3 and PA4 ports of the MCU, and their on / off states are controlled by the levels of the PA1, PA2, PA3 and PA4 ports; the resistor R2 is connected between the inverting input terminal of the operational amplifier OP1 and the ground, the NMOS transistor Q5 and the resistor R7 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q6 and the resistor R8 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q7 and the resistor R9 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q8 and the resistor R 10It is connected in series between the inverting input terminal and the output terminal of the operational amplifier OP1. The gates of the NMOS transistors Q5, Q6, Q7, and Q8 are respectively connected to the PA1, PA2, PA3, and PA4 ports of the MCU, and their on / off states are controlled by the levels of the PA1, PA2, PA3, and PA4 ports. The non-inverting input terminal of the operational amplifier OP2 is connected to the output terminal of the operational amplifier OP1, and the inverting input terminal of the operational amplifier OP2 is connected to the output terminal of the operational amplifier OP2, realizing buffering and isolation of the output signal v o1 of the operational amplifier OP1 and obtaining the output signal v o , reducing the load effect of the signal and ensuring the integrity of the v o1 signal.

[0008] In the aforementioned current measurement system for a high-frequency electrosurgical unit, in the signal conditioning circuit module, the resistance values of the respective resistors satisfy the following relationships:

[0009] R1 = R2, R3 = R7 = 10R1, R4 = R8 = 50R1, R5 = R9 = 200R1, R6 = R 10 = 1000R1.

[0010] In the aforementioned current measurement system for a high-frequency electrosurgical unit, in the signal conditioning circuit module, the NMOS transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 are of the same model, and the on-resistance in the saturation conduction state is 20 - 70 milliohms.

[0011] In the aforementioned current measurement system for a high-frequency electrosurgical unit, the filter circuit is an active filter circuit or a passive filter circuit.

[0012] The measurement method of the aforementioned current measurement system for a high-frequency electrosurgical unit includes the following steps:

[0013] Step 1: Convert the current of the high-frequency electrosurgical unit into a corresponding voltage signal through a current-to-voltage module;

[0014] Step 2: The signal conditioning circuit module performs high-frequency interference filtering, amplification, and DC bias processing on the voltage signal;

[0015] Step 3: The filter circuit filters out high-frequency interference from the signal at the output terminal of the signal conditioning circuit module to obtain a sampled voltage, and the sampled voltage is input to the AD port of the MCU;

[0016] Step 4: The MCU samples the sampled voltage to calculate the effective value of the current, and then calculates the value and displays it through the display module. At the same time, the size and amplification factor of the DC bias voltage of the conditioning circuit are regulated according to the effective value of the current.

[0017] In the aforementioned measurement method, when in light load and when the operating frequency of the high-frequency electrosurgical unit is low, the MCU increases the amplification factor of the signal conditioning circuit module and reduces the DC bias voltage; when the operating frequency of the high-frequency electrosurgical unit is high and the corresponding effective current value is large, the MCU reduces the amplification factor of the signal conditioning circuit module and increases the DC bias voltage.

[0018] In the aforementioned measurement method, during the process of filtering out high-frequency interference and anti-aliasing, the filtering circuit selects appropriate active filtering circuit or passive filtering circuit parameters according to the frequency characteristics and sampling requirements to ensure the accuracy of the sampled voltage.

[0019] Compared with the prior art, the current measurement system of the present invention can automatically adjust the amplification factor and DC bias voltage of the signal conditioning circuit according to the magnitude of the high-frequency electrosurgical unit current, adapt to the measurement requirements at different frequencies, and effectively improve the measurement accuracy. The signal conditioning circuit module of the present invention adopts a specific combination of resistors and MOS transistors, flexibly adjusts the amplification factor by controlling the port level, and uses a voltage follower to ensure the integrity of the signal and reduce the distortion during signal transmission. The filtering circuit of the present invention can select active or passive filtering methods according to actual needs, effectively filter out high-frequency interference and prevent aliasing, provide an accurate sampled voltage for the MCU, and further improve the measurement accuracy. The MCU and display module of the present invention can not only accurately calculate and display values, but also monitor the system status in real time, detect and display fault information in a timely manner, and facilitate the user to manage and maintain the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a circuit schematic diagram of the present invention;

[0021] Figure 2 is a schematic diagram of the measurement algorithm flow of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will be further described below in conjunction with embodiments and the drawings, but it shall not be used as a basis for limiting the present invention.

[0023] Embodiment 1: A current measurement system for a high-frequency electrosurgical unit, as shown in the attached Figure 1 figure, includes a current-to-voltage conversion module, a signal conditioning circuit module, a filtering circuit, an MCU and a display module.

[0024] The current-to-voltage conversion module is composed of a current transformer CT and a resistor R c ; the input coil of the current transformer CT is used to receive the current of the high-frequency electrosurgical unit; the resistor R c is connected in parallel across the output coil of the current transformer CT, and one end of the resistor R c is grounded. The turns ratio of the current transformer CT is N, and the input current i of the CTac Decay to i ac / N is output via the secondary side coil of the CT. The resistor R c Converts i ac / N into a voltage signal v ac . By selecting the value of N, the coefficient adjustment between v ac and i ac can be achieved. Therefore, v ac and i ac satisfy the following formula:

[0025]

[0026] Obviously, by reasonably selecting the values of N and R c the magnification between v ac and i ac can be controlled.

[0027] The signal conditioning circuit module includes a capacitor C in_filter , resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, resistor R 10 , NMOS transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, operational amplifier OP1 and operational amplifier OP2; the resistor R1 is connected between the current-to-voltage module and the non-inverting input terminal of the operational amplifier OP1, and C in_filter is connected between the non-inverting input terminal of OP1 and the ground; the NMOS transistor Q1 and the resistor R3 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of the operational amplifier OP1, the NMOS transistor Q2 and the resistor R4 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1, the NMOS transistor Q3 and the resistor R5 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1, the NMOS transistor Q4 and the resistor R6 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1; the gates of the NMOS transistors Q1, Q2, Q3 and Q4 are respectively connected to the PA1, PA2, PA3 and PA4 ports of the MCU, and their on / off is controlled by the levels of the PA1, PA2, PA3 and PA4 ports; the resistor R2 is connected between the inverting input terminal of the operational amplifier OP1 and the ground, the NMOS transistor Q5 and the resistor R7 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q6 and the resistor R8 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q7 and the resistor R9 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q8 and the resistor R 10It is connected in series between the inverting input terminal and the output terminal of the operational amplifier OP1. The gates of the NMOS transistors Q5, Q6, Q7, and Q8 are respectively connected to the PA1, PA2, PA3, and PA4 ports of the MCU, and their on / off states are controlled by the levels of the PA1, PA2, PA3, and PA4 ports. The non-inverting input terminal of the operational amplifier OP2 is connected to the output terminal of the operational amplifier OP1, and the inverting input terminal of the operational amplifier OP2 is connected to the output terminal of the operational amplifier OP2, realizing buffering and isolation of the output signal v o1 and obtaining the output signal v o , reducing the load effect of the signal and ensuring the integrity of the v o1 signal. The above C1 and R1 form a first-order RC low-pass filter circuit to filter out the high-frequency interference of v ac and the spikes generated when i ac changes sharply. At the same time, the resistors satisfy: R1 = R2, R3 = R7 = 10R1, R4 = R8 = 50R1, R5 = R9 = 200R1, R6 = R 10 = 1000R1. The NMOS transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 are of the same model and the saturation conduction internal resistance is only dozens (20 - 70) milliohms. OP2 is a voltage follower, realizing buffering and isolation of the output signal v o1 of OP1 and obtaining the output signal v o , reducing the high-frequency electrosurgical effect of the signal and ensuring the integrity of the v o1 signal. By controlling the levels of the PA1, PA2, PA3, and PA4 ports, the amplification factor of the signal conditioning circuit module can be adjusted. When PA1 = 1, PA2 = PA3 = PA4 = 0, Q1 and Q5 are saturated and conducting, and Q2, Q3, Q4, Q6, Q7, and Q8 are cut off. The resistor connected between the inverting input terminal of OP1 and the output terminal v o1 is R7, and the resistor connected between the non-inverting input terminal of OP1 and V ref is R3. According to electrical engineering knowledge, v o1 and v ac satisfy the following formula:

[0028] v o1 = V ref + v ac R3 / R1 = V ref + 10v ac (2)

[0029] Similarly, when PA2 = 1, PA1 = PA3 = PA4 = 0, Q2 and Q6 are saturated and conducting, and Q1, Q3, Q4, Q5, Q7, and Q8 are cut off. The resistor connected between the inverting input terminal of OP1 and the output terminal v o1The resistance between them is R8, and the resistance connected between the non-inverting input terminal of OP1 and V ref is R4. According to the knowledge of electrical engineering, it is known that: v o1 and v ac satisfy the following formula:

[0030] v o1 = V ref + v ac R4 / R1 = V ref + 50v ac (2)

[0031] And so on, when PA3 = 1, PA1 = PA2 = PA4 = 0, v o1 and v ac satisfy the following formula:

[0032] v o1 = V ref + v ac R5 / R1 = V ref + 200v ac (3)

[0033] When PA4 = 1, PA1 = PA2 = PA3 = 0, v o1 and v ac satisfy the following formula:

[0034] v o1 = V ref + v ac R6 / R1 = V ref + 1000v ac (4)

[0035] Therefore, the MCU can adjust the amplification factor of v o1 and v ac by controlling the states of the PA1, PA2, PA3, and PA4 ports.

[0036] The filter circuit can be composed of an active filter circuit or a passive filter circuit to achieve high-frequency and anti-aliasing filtering of v o , filter out the interference of v o to obtain the sampled voltage v samp , and output it to the AD sampling port of the MCU.

[0037] The microprocessor MCU samples v samp and calculates the effective value I ac of the high-frequency electrosurgical current i RMS and the corresponding relationship between I RMS and calculates the value, and displays the value and fault information through the LCD. At the same time, due to the large change range at high frequency or low frequency, the corresponding current iac The effective value I RMS also has a large variation range. At low frequencies, I RMS has a very small value, and the corresponding DC bias voltage V ref is also very small. However, in order to achieve high-resolution measurement, a very small current requires a large amplification factor. Similarly, at high frequencies, the current I RMS has a very large value, and the corresponding DC bias voltage V ref is also very large. In order to ensure that the voltage signal v o does not exceed the linear amplification range of the operational amplifier and the AD sampling voltage range, the required amplification factor is very small. Therefore, the MCU will dynamically adjust the magnitude of the DC bias voltage V RMS output from the DA port according to the magnitude range of I ref .

[0038] Embodiment 2: Based on the current measurement system for a high-frequency electrosurgical unit in Embodiment 1, this embodiment provides a measurement method, as Figure 2 shown, including the following steps:

[0039] Step 1: Convert the current of the high-frequency electrosurgical unit into a corresponding voltage signal through a current-to-voltage module;

[0040] Step 2: The signal conditioning circuit module performs high-frequency interference filtering, amplification, and DC biasing on the voltage signal;

[0041] Step 3: The filter circuit filters out high-frequency interference from the signal at the output end of the signal conditioning circuit module to obtain a sampling voltage, and inputs the sampling voltage to the AD port of the MCU;

[0042] Step 4: The MCU samples the sampling voltage to calculate the effective value of the current, and then calculates the value and displays it through the display module. At the same time, it adjusts the magnitude of the DC bias voltage and the amplification factor of the conditioning circuit according to the effective value of the current.

[0043] When at low frequencies, the corresponding effective value of the current is small, and the MCU increases the amplification factor of the signal conditioning circuit module and reduces the DC bias voltage; when at high frequencies, the corresponding effective value of the current is large, and the MCU reduces the amplification factor of the signal conditioning circuit module and increases the DC bias voltage.

[0044] In summary, the current measurement system of the present invention can automatically adjust the amplification factor and DC bias voltage of the signal conditioning circuit according to the magnitude of the high-frequency electrosurgical current, adapt to the current measurement requirements at different frequencies, and effectively improve the measurement accuracy. The signal conditioning circuit module of the present invention adopts a specific combination of resistors and MOS transistors, flexibly adjusts the amplification factor by controlling the port level, and uses a voltage follower to ensure the integrity of the signal, reducing signal distortion during transmission. The filtering circuit of the present invention can select active or passive filtering methods according to actual needs, effectively filter out high-frequency interference and prevent aliasing, provide an accurate sampling voltage for the MCU, and further improve the measurement accuracy. The MCU and display module of the present invention can not only accurately calculate and display values, but also monitor the system status in real time, discover and display fault information in a timely manner, facilitating users to manage and maintain the system.

Claims

1. A current measurement system for a high-frequency electrosurgical unit, characterized in that: It includes a current-to-voltage module, a signal conditioning circuit module, a filtering circuit, an MCU, and a display module connected in sequence; the current-to-voltage module is used to convert the current of the high-frequency electrotome into a corresponding voltage signal; the signal conditioning circuit module first filters the high-frequency interference of the voltage signal and amplifies and applies a DC bias to the filtered signal; the filtering circuit is used to filter the high-frequency interference from the signal at the output end of the signal conditioning circuit module to obtain a sampled voltage; the MCU samples the sampled voltage and calculates the effective value I of the output current RMS , and controls the size of the DC bias voltage and the amplification factor control of the signal conditioning circuit according to the size of the effective value I RMS ; the display module is used to display the measured effective value I RMS .

2. The current measurement system for a high-frequency electrosurgical unit according to claim 1, wherein: The current-to-voltage module consists of a current transformer CT and a resistor R c ; the input coil of the current transformer CT is used to receive the output current of the high-frequency electrotome; the resistor R c is connected in parallel across the output coil of the current transformer CT, and one end of the resistor R c is grounded.

3. The current measurement system for a high-frequency electrosurgical unit according to claim 1, characterized in that: The signal conditioning circuit module includes capacitor C in_filter , resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, resistor R 10 , NMOS transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, Q8, operational amplifier OP1 and operational amplifier OP2; The resistor R1 is connected between the current-to-voltage module and the non-inverting input terminal of the operational amplifier OP1, and C in_filter is connected between the non-inverting input terminal of OP1 and the ground; The NMOS transistor Q1 and the resistor R3 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of the operational amplifier OP1, the NMOS transistor Q2 and the resistor R4 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1, the NMOS transistor Q3 and the resistor R5 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1, the NMOS transistor Q4 and the resistor R6 are connected in series between the DA terminal of the MCU and the non-inverting input terminal of OP1; The gate electrodes of the NMOS transistors Q1, Q2, Q3 and Q4 are respectively connected to the PA1, PA2, PA3 and PA4 ports of the MCU, and their on / off states are controlled by the levels of the PA1, PA2, PA3 and PA4 ports; The resistor R2 is connected between the inverting input terminal of the operational amplifier OP1 and the ground, the NMOS transistor Q5 and the resistor R7 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q6 and the resistor R8 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q7 and the resistor R9 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the NMOS transistor Q8 and the resistor R 10 are connected in series between the inverting input terminal of the operational amplifier OP1 and the output terminal of the operational amplifier OP1, the gate electrodes of the NMOS transistors Q5, Q6, Q7 and Q8 are respectively connected to the PA1, PA2, PA3 and PA4 ports of the MCU, and their on / off states are controlled by the levels of the PA1, PA2, PA3 and PA4 ports; The non-inverting input terminal of the operational amplifier OP2 is connected to the output terminal of the operational amplifier OP1, and the inverting input terminal of the operational amplifier OP2 is connected to the output terminal of the operational amplifier OP2, realizing buffering and isolation of the output signal v o1 of the operational amplifier OP1 and obtaining the output signal v o , reducing the load effect of the signal and ensuring the integrity of the v o1 signal.

4. The current measurement system for a high-frequency electrosurgical unit according to claim 3, characterized in that: In the signal conditioning circuit module, the resistance values of the resistors satisfy the following relationship: R1 = R2, R3 = R7 = 10R1, R4 = R8 = 50R1, R5 = R9 = 200R1, R6 = R 10 = 1000R1。 5. The current measurement system for a high-frequency electrosurgical unit according to claim 3, wherein: In the signal conditioning circuit module, the NMOS transistors Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 are of the same model, and the on-resistance in saturation is 20 - 70 milliohms.

6. The current measurement system for a high-frequency electrosurgical unit according to claim 1, wherein: The filter circuit is an active filter circuit or a passive filter circuit.

7. The measuring method of the current measuring system for a high-frequency electrotome according to any one of claims 1-6, characterized in that: It includes the following steps: Step 1: Convert the current of the high-frequency electrosurgical unit into a corresponding voltage signal through the current-to-voltage module. Step 2: The signal conditioning circuit module performs high-frequency interference filtering, amplification, and DC biasing on the voltage signal. Step 3: The filter circuit filters out high-frequency interference from the signal at the output end of the signal conditioning circuit module to obtain a sampled voltage, and inputs the sampled voltage to the AD port of the MCU. Step 4: The MCU samples the sampled voltage to calculate the effective current value, and then calculates and displays the value through the display module. At the same time, according to the effective current value, it regulates the magnitude of the DC bias voltage and the amplification factor of the conditioning circuit.

8. The measuring method according to claim 7, characterized in that: When the operating frequency of the high-frequency electrosurgical unit is low, the corresponding effective current value is small, and the MCU increases the amplification factor of the signal conditioning circuit module and reduces the DC bias voltage; when the operating frequency of the high-frequency electrosurgical unit is high, the corresponding effective current value is large, and the MCU reduces the amplification factor of the signal conditioning circuit module and increases the DC bias voltage.

9. The measuring method according to claim 7, characterized in that: During the process of filtering out high-frequency interference and anti-aliasing, the filter circuit selects appropriate parameters of the active filter circuit or passive filter circuit according to the frequency characteristics and sampling requirements to ensure the accuracy of the sampled voltage.

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