High-precision high-interference-resistant high-voltage type pascal meter

Abstract

The application relates to a high-precision high-anti-interference high-voltage picoammeter, and belongs to the technical field of instrument control measurement. The picoammeter comprises a program-controlled high-voltage module, a digital-analog conversion module DAC, an analog-digital conversion module ADC, a controller, a transimpedance operational amplifier U1A and a secondary operational amplifier U1B; the controller is connected with the digital-analog conversion module DAC and the analog-digital conversion module ADC respectively; the program-controlled high-voltage module is connected with the digital-analog conversion module DAC and the analog-digital conversion module ADC respectively; the output end of the transimpedance operational amplifier U1A is connected with the non-inverting input end of the secondary operational amplifier U1B, and the secondary operational amplifier U1B is connected with the analog-digital conversion module ADC. The program-controlled high-voltage power supply and the picoammeter are integrated, the picoammeter has the functions of picoampere-level micro-current measurement and programmable high-voltage output, can meet the micro-current measurement, can realize the simultaneous shielding of the microammeter and the high-voltage power supply, and can avoid the inaccuracy of current measurement caused by the adjustment of the shielding layer.

Description

Technical Field

[0001] This invention belongs to the field of instrumentation and measurement technology, specifically relating to a high-precision, high-interference, high-voltage picoammeter. Background Technology

[0002] In existing measurements such as ion measurement and electron beam measurement, picoammeters and programmable power supplies are two independent standard instruments. When used together, the following problems exist: First, the programmable power supply and picoammeter are coupled to a common ground, which can easily cause external electric fields to affect the current value, especially at low currents, resulting in inaccurate readings. Second, the programmable power supply and picoammeter are not under unified control, and improper operation can easily damage the picoammeter. Third, they are bulky and difficult to embed in some devices, while external placement can lead to interference and inaccurate measurements.

[0003] Therefore, a new solution is needed to address this problem. Summary of the Invention

[0004] The present invention mainly addresses the technical problems existing in the prior art and provides a high-precision, high-interference, high-voltage picoammeter.

[0005] The above-mentioned technical problems of the present invention are mainly solved by the following technical solution: a high-precision, high-interference, high-voltage picoammeter, comprising a programmable high-voltage module, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), a controller, a transimpedance operational amplifier (U1A), and a second-stage operational amplifier (U1B). The controller is connected to both the DAC and the ADC. The programmable high-voltage module is connected to both the DAC and the ADC. The output of the transimpedance operational amplifier (U1A) is connected to the non-inverting input of the second-stage operational amplifier (U1B), and is connected to the ADC through the second-stage operational amplifier (U1B).

[0006] The controller controls the programmable high voltage output of the programmable high voltage module by outputting analog voltage through the digital-to-analog converter (DAC). The output high voltage is divided and then sent to the analog-to-digital converter (ADC). The controller reads the ADC voltage value and corrects the analog voltage value of the DAC to achieve programmable high voltage power supply output.

[0007] The transimpedance operational amplifier U1A converts the input micro-current into voltage, which is then amplified by the secondary operational amplifier U1B and sent to the analog-to-digital converter (ADC). The controller reads the ADC voltage value and calculates the input micro-current value to achieve micro-current measurement.

[0008] Preferably, the transimpedance operational amplifier U1A is connected to a programmable switch SW1, and the secondary operational amplifier U1B is connected to a programmable switch SW2. The programmable switches SW1 and SW2 work together to achieve 10 levels of transimpedance amplification, with each level having an interval amplification factor of 10.

[0009] Preferably, the inverting input of the transimpedance operational amplifier U1A is connected to a programmable switch SW1. The five positions of the programmable switch SW1 are respectively connected to sampling resistors of different resistance values, and the sampling resistors are respectively connected to the output of the transimpedance operational amplifier U1A and the non-inverting input of the secondary operational amplifier U1B. The inverting input of the secondary operational amplifier U1B is respectively connected to one end of the feedback resistor R6 and one end of the feedback resistor R7. The other end of the feedback resistor R6 is grounded. The output of the secondary operational amplifier U1B is connected to the other end of the feedback resistor R7. The analog-to-digital converter (ADC) is connected to a programmable switch SW2. One position of the programmable switch SW2 is connected to the sampling resistor, and the other position of the programmable switch SW2 is connected to the output of the secondary operational amplifier U1B.

[0010] Preferably, the system also includes an isolated power supply and an isolated communication module, wherein the isolated power supply is connected to the programmable high-voltage module and the isolated communication module is connected to the controller.

[0011] Preferably, the microcurrent measurement method is as follows: the controller reads the ADC voltage value and determines the ammeter range based on the ADC voltage value's range; when the ADC voltage value is less than 0.1 times the full-scale value, the range automatically increases by 1, and the preamplifier gain increases by 10 times; when the ADC voltage value is greater than 0.9 times the full-scale value, the range automatically decreases by 1, and the preamplifier gain decreases by 10 times; when the ADC voltage value is between 0.1 and 0.9 times the full-scale value, the input current value is calculated based on the current ADC voltage value, the range coefficient, and the correction coefficient. The formula for calculating the input current is:

[0012] I=(ADC-Offset[range])*K[range]*pow(10,-2-1*range);

[0013] In the formula, range is the current gear, with a value of 0 to 9; the Offset[range] array is the zero-point deviation of the instrument when the gear is 0 to 9, which is the factory calibration; the K[range] array is the proportional coefficient value of the instrument when the gear is 0 to 9, which is the factory calibration.

[0014] As a preferred method, the output method of the programmable high-voltage power supply is as follows: the controller reads the target voltage to be output, reduces the target voltage by 1000 times, and outputs it to the digital-to-analog converter (DAC). The DAC outputs an analog voltage to control the high-voltage output of the programmable high-voltage module. The output high voltage is reduced by 1 / 1000 and sent to the analog-to-digital converter (ADC). The controller calculates the high voltage to be read back based on the ADC voltage value and performs closed-loop correction between the read-back high voltage and the target voltage to adjust the analog voltage value of the DAC, thereby achieving the purpose of accurately outputting high voltage.

[0015] The beneficial effects of this invention are as follows: This invention integrates a programmable high-voltage power supply and a picoammeter into one unit, providing picoammeter-level micro-current measurement and programmable high-voltage output functions. It satisfies the requirements for micro-current measurement while simultaneously shielding both the micro-ammeter and the high-voltage power supply, preventing inaccurate current measurements caused by shifting of the shielding layer. Furthermore, the integrated design allows for added hardware protection and software diagnostic functions to prevent damage from short circuits in the high-voltage power supply or damage to the picoammeter caused by the high-voltage power supply. This invention offers superior reliability and significantly reduces the size after integration, facilitating integration into intelligent sensors such as ionization chambers and ion beam measurements. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Figure 2 This is a schematic diagram of an operation process of the present invention;

[0018] Figure 3 This is a circuit diagram of a programmable high-voltage power supply output according to the present invention.

[0019] In the diagram: 1. Programmable high-voltage module; 2. Digital-to-analog converter (DAC); 3. Analog-to-digital converter (ADC); 4. Controller; 5. Isolated power supply; 6. Isolated communication module. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0021] Example: A high-precision, high-interference, high-voltage picoammeter, such as... Figures 1-3As shown, the system includes a programmable high-voltage module 1, a digital-to-analog converter (DAC) module 2, an analog-to-digital converter (ADC) module 3, a controller 4, an isolation power supply 5, an isolation communication module 6, a transimpedance operational amplifier U1A, and a secondary operational amplifier U1B. The isolation power supply 5 is connected to the programmable high-voltage module 1. The controller 4 is connected to the DAC, ADC, and isolation communication modules 6. The programmable high-voltage module 1 is connected to both the DAC and ADC modules. The output of the transimpedance operational amplifier U1A is connected to the non-inverting input of the secondary operational amplifier U1B, and the secondary operational amplifier U1B is connected to the ADC module 3.

[0022] The controller 4 controls the programmable high voltage output of the programmable high voltage module 1 by outputting analog voltage through the digital-to-analog converter module DAC2. The output high voltage is divided and sent to the analog-to-digital converter module ADC3. The controller 4 reads the ADC voltage value and corrects the analog voltage value of the digital-to-analog converter module DAC2 to realize the programmable high voltage power supply output.

[0023] The transimpedance operational amplifier U1A converts the input micro-current into voltage, which is then amplified by the secondary operational amplifier U1B and sent to the analog-to-digital converter module ADC3. The controller 4 reads the ADC voltage value and calculates the input micro-current value to achieve micro-current measurement.

[0024] The isolation power supply 5 is connected to an external 5V power supply and supplies power to each module through the isolation power supply 5. By setting up the isolation power supply 5, ground coupling problems can be effectively isolated and crosstalk can be avoided. Through the cooperation of the isolation power supply 5 and the isolation communication module 6, the programmable high-voltage power output and micro-current measurement have separate isolation grounds and are completely shielded. In this way, power supply and communication noise will not affect the external high-voltage output and micro-current measurement, thereby achieving high anti-interference capability of the system.

[0025] In this embodiment, the programmable high voltage module 1, the digital-to-analog converter module DAC2, the analog-to-digital converter module ADC3, and the isolation communication module 6 are all existing technology module circuits, so the circuit parts of each module will not be described in detail. This invention focuses on the connection and cooperation of each module to realize the integration of the programmable high voltage power supply and the picoammeter into one unit, which not only satisfies the measurement of micro current, but also achieves simultaneous shielding of the microammeter and the high voltage power supply. This can avoid inaccurate current measurement caused by the movement of the shielding layer.

[0026] In this embodiment, the controller 4 mainly implements the input of external commands and the output of measurement feedback.

[0027] Because programmable high-voltage power supplies require a relatively high output bias voltage (500–3000V) and a relatively low operating current (below 1mA), a switching power supply with a voltage doubler rectifier circuit is used to achieve this. Figure 3As shown, the target output voltage is reduced by a factor of 1000 (1000V corresponds to an output voltage of 1V), and then the analog voltage HVSET is output through the digital-to-analog converter module DAC2. This analog voltage serves as the non-inverting input of the comparator LM2903, and is compared with the feedback power supply to determine the operating state of the switching power supply. The switching power supply controls the MOSFET M4, which, in conjunction with the inductor L2, generates an oscillating voltage. This voltage is then rectified by diodes and capacitors at the back end to form a multiplied output voltage, thus increasing the voltage from 5V to a maximum of 3000V. The output voltage is then divided by high-voltage resistors R15, R16, R17, R18, and R19, and then fed into the analog-to-digital converter module ADC3 via the follower operational amplifier U5A for voltage-to-digital conversion. The controller 4 reads the ADC voltage value and corrects the analog voltage HVSET value of the digital-to-analog converter module DAC2, thereby achieving high-precision high-voltage output.

[0028] In micro-current measurement, to achieve a wide current input range, both the transimpedance operational amplifier and the secondary operational amplifier employ programmable gain. Specifically, the transimpedance operational amplifier U1A is connected to a 5-to-1 programmable switch SW1, and the secondary operational amplifier U1B is connected to a 2-to-1 programmable switch SW2. The programmable switches SW1 and SW2 work together to achieve 10 levels of transimpedance amplification, with each level having a gain interval of 10. Specifically:

[0029] The inverting input of the transimpedance operational amplifier U1A is connected to the programmable switch SW1. The five positions of the programmable switch SW1 are connected to sampling resistors of different resistance values, and through the sampling resistors, they are connected to the output of the transimpedance operational amplifier U1A and the non-inverting input of the secondary operational amplifier U1B. The inverting input of the secondary operational amplifier U1B is connected to one end of the feedback resistor R6 and one end of the feedback resistor R7. The other end of the feedback resistor R6 is grounded. The output of the secondary operational amplifier U1B is connected to the other end of the feedback resistor R7. The analog-to-digital converter module ADC3 is connected to the programmable switch SW2. One position of the programmable switch SW2 is connected to the sampling resistor, and the other end of the programmable switch SW2 is connected to the output of the secondary operational amplifier U1B.

[0030] The sampling resistors R1, R2, R3, R4, and R5 have a resistance of 100Ω, 10KΩ, 1MΩ, 100MΩ, and 10GΩ, respectively, to achieve amplification factors of 100V / A, 10KV / A, 1000KV / A, 108V / A, and 1010V / A. The feedback resistors R6 and R7 have a resistance of 10KΩ and a resistance of 90KΩ, respectively, to achieve a 10x amplification factor.

[0031] During micro-current measurement, the micro-current input is achieved through the transimpedance operational amplifier U1A. Programmable switch SW2 determines whether the voltage after the transimpedance operational amplifier U1A is directly input to the analog-to-digital converter (ADC3) module, or amplified 10 times before being connected to ADC3. By coordinating programmable switches SW1 and SW2, a total of 10 transimpedance amplification factors ranging from 100V / A to 1011V / A can be achieved, with each factor increment being 10, as shown in Table 1.

[0032] Table 1. Amplification and Current Range of Pimoammeter at Each Range

[0033] gear Magnification Current range 0 10mA / V 20mA~2mA 1 1mA / V 2mA~0.2mA 2 100uA / V 200uA~20uA 3 10uA / V 20uA~2uA 4 1uA / V 2uA~200nA 5 100nA / V 200nA~20nA 6 10nA / V 20nA~2nA 7 1nA / V 2nA~0.2nA 8 100pA / V 200pA~20pA 9 10pA / V <20pA

[0034] like Figure 2 As shown, the microcurrent measurement method is as follows:

[0035] Controller 4 reads the ADC voltage value and determines the ammeter range based on the ADC voltage range. The full-scale range of the ADC is ±2V. When the ADC voltage value is less than 0.1 times the full-scale value (less than 0.2V), the range automatically increases by 1, and the preamplifier gain increases by 10 times to improve the input voltage and increase measurement resolution and accuracy. When the ADC voltage value is greater than 0.9 times the full-scale value (greater than 1.8V), the range automatically decreases by 1, and the preamplifier gain decreases by 10 times to avoid excessive input voltage overflow, which could cause measurement errors and ensure the measurement range is maintained. When the ADC voltage value is between 0.1 and 0.9 times the full-scale value, the input current value is calculated based on the current ADC voltage value, range coefficient, and correction coefficient. The formula for calculating the input current is:

[0036] I=(ADC-Offset[range])*K[range]*pow(10,-2-1*range);

[0037] In the formula, range represents the current gear, with a value of 0 to 9;

[0038] The Offset[range] array represents the zero-point deviation of the instrument when the gear is 0 to 9, according to the factory calibration.

[0039] The K[range] array represents the proportional coefficient value of the instrument when the gear is 0 to 9, as per factory calibration.

[0040] The output method of the programmable high-voltage power supply is as follows:

[0041] The controller 4 reads the target voltage to be output, reduces the target voltage by 1000 times (1000V corresponds to an output voltage of 1V), and outputs it to the digital-to-analog converter module DAC2. The DAC calculates the output analog voltage, and the analog voltage output by the digital-to-analog converter module DAC2 controls the high voltage output of the programmable high voltage module 1. The output high voltage is reduced by 1 / 1000 and then sent to the analog-to-digital converter module ADC3. The controller 4 calculates the high voltage to be read back based on the ADC voltage value, and performs closed-loop correction between the read-back high voltage and the target voltage to adjust the analog voltage value of the digital-to-analog converter module DAC2, thereby achieving the purpose of accurately outputting high voltage.

[0042] The voltage closed-loop control uses PID regulation.

[0043] Err = HVFB - HVSET; / / Calculation error

[0044] Err.Integal += Err; / / Error integral

[0045] HVSET+=kp*Err+ki*Err.Integal+kd*(Err-Err.Last);

[0046] Err.Last = Error;

[0047] In the formula: HVFB and HVSET are the feedback high voltage value and the set high voltage value, respectively; Err.Integal is the error integral value; Err.Last is the previous error value.

[0048] In summary, this invention integrates a programmable high-voltage power supply and a picoammeter into a single unit, providing picoammeter-level micro-current measurement and programmable high-voltage output. It satisfies the need for micro-current measurement while simultaneously shielding both the micro-ammeter and the high-voltage power supply, preventing inaccurate current measurements caused by shielding layer movement. Furthermore, the integrated design allows for added hardware protection and software diagnostic functions to prevent damage from short circuits in the high-voltage power supply or damage to the picoammeter caused by the high-voltage power supply. This invention offers superior reliability and significantly reduces the overall size after integration, facilitating integration into intelligent sensors such as ionization chambers and ion beam measurements.

[0049] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention should be considered within the protection scope of the present invention.

Claims

1. A high-precision, high-interference, high-voltage picoammeter, characterized in that, The system includes a programmable high-voltage module (1), a digital-to-analog converter (DAC) module (2), an analog-to-digital converter (ADC) module (3), a controller (4), a transimpedance operational amplifier U1A, and a secondary operational amplifier U1B. The controller (4) is connected to the digital-to-analog converter (DAC) module (2) and the analog-to-digital converter (ADC) module (3) respectively. The programmable high-voltage module (1) is connected to the digital-to-analog converter (DAC) module (2) and the analog-to-digital converter (ADC) module (3) respectively. The output terminal of the transimpedance operational amplifier U1A is connected to the non-inverting input terminal of the secondary operational amplifier U1B, and is connected to the analog-to-digital converter (ADC) module (3) through the secondary operational amplifier U1B. The controller (4) outputs analog voltage through the digital-to-analog converter module DAC (2) to control the programmable high voltage output of the programmable high voltage module (1). The output high voltage is divided and sent to the analog-to-digital converter module ADC (3). The controller (4) reads the ADC voltage value and corrects the analog voltage value of the digital-to-analog converter module DAC (2) to realize the programmable high voltage power supply output. The transimpedance operational amplifier U1A converts the input micro current into voltage, which is then amplified by the secondary operational amplifier U1B and sent to the analog-to-digital converter module ADC (3). The controller (4) reads the ADC voltage value and calculates the input micro current value to realize micro current measurement. The transimpedance operational amplifier U1A is connected to a programmable switch SW1, and the secondary operational amplifier U1B is connected to a programmable switch SW2. The programmable switches SW1 and SW2 work together to achieve 10 levels of transimpedance amplification, with each level having an interval amplification factor of 10. The inverting input of the transimpedance operational amplifier U1A is connected to a programmable switch SW1. The five positions of the programmable switch SW1 are connected to sampling resistors of different resistance values, and these sampling resistors are connected to the output of the transimpedance operational amplifier U1A and the non-inverting input of the secondary operational amplifier U1B, respectively. The inverting input of the secondary operational amplifier U1B is connected to one end of feedback resistor R6 and one end of feedback resistor R7, respectively. The other end of feedback resistor R6 is grounded. The output of the secondary operational amplifier U1B is connected to the other end of feedback resistor R7. The analog-to-digital converter (ADC) is connected to a programmable switch SW2. One position of the programmable switch SW2 is connected to a sampling resistor, and another position of the programmable switch SW2 is connected to the output of the secondary operational amplifier U1B. The sampling resistor R1 has a resistance of 100Ω, the sampling resistor R2 has a resistance of 10KΩ, the sampling resistor R3 has a resistance of 1MΩ, the sampling resistor R4 has a resistance of 100MΩ, and the sampling resistor R5 has a resistance of 10GΩ, to achieve current and voltage of 100V / A, 10KV / A, and 1000KV / A. V / A, The amplification factor is V / A; the resistance of feedback resistor R6 is 10KΩ and the resistance of feedback resistor R7 is 90KΩ, so as to achieve a 10x amplification factor. The method for measuring microcurrent is as follows: The controller (4) reads the ADC voltage value and determines the range of the ammeter according to the range of the ADC voltage value; when the ADC voltage value is less than 0.1 times the full scale value, the range is automatically increased by 1, and the preamplifier amplification factor is increased by 10 times; when the ADC voltage value is greater than 0.9 times the full scale, the range is automatically decreased by 1, and the preamplifier amplification factor is reduced by 10 times; when the ADC voltage value is between 0.1 and 0.9 times the full scale, the input current value is calculated according to the current ADC voltage value, range coefficient and correction coefficient. The formula for calculating the input current is: ； In the formula, range is the current gear, with a value of 0 to 9; the Offset[range] array is the zero-point deviation of the instrument when the gear is 0 to 9, which is the factory calibration; the K[range] array is the proportional coefficient value of the instrument when the gear is 0 to 9, which is the factory calibration. The output method of the programmable high voltage power supply is as follows: the controller (4) reads the target voltage to be output, reduces the target voltage by 1000 times and outputs it to the analog-to-digital converter module (DAC) (2). The analog-to-digital converter module (DAC) (2) outputs analog voltage to control the high voltage output of the programmable high voltage module (1). The high voltage output is reduced by 1 / 1000 and sent to the analog-to-digital converter module (ADC) (3). The controller (4) calculates the high voltage read back according to the ADC voltage value and performs closed-loop correction between the high voltage read back and the target voltage to adjust the analog voltage value of the analog-to-digital converter module (DAC) (2), thereby achieving the purpose of accurately outputting high voltage.

2. The high-precision, high-interference, high-voltage picoammeter according to claim 1, characterized in that, It also includes an isolation power supply (5) and an isolation communication module (6), wherein the isolation power supply (5) is connected to the programmable high voltage module (1) and the isolation communication module (6) is connected to the controller (4).

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