Picoampere-level ion current detection device

Abstract

The utility model discloses a picoampere-level ion current detection device, which belongs to the technical field of ion detection and comprises an ion current amplification circuit, a main operational amplifier circuit, an analog-to-digital conversion circuit and a single chip microcomputer which are sequentially connected. The ion current amplification circuit comprises a detection circuit, a first-stage operational amplifier circuit and a second-stage operational amplifier circuit which are connected in sequence; the analog-to-digital conversion circuit comprises an analog-to-digital converter and an optical coupler which are connected in sequence. The device provides a high-precision operational amplifier which is small in offset, high in gain, strong in common-mode rejection capability, fast in response, low in drift and stable in performance through multi-stage operational amplification, anti-interference and analog-to-digital conversion, outputs real, reliable, stable and easy-to-process electric signals, and realizes a precise detection function of low-power-consumption picoampere-level weak signals.

Description

Technical Field

[0001] This utility model relates to the field of ion detection technology, and in particular to a picoampere-level ion current detection device. Background Technology

[0002] In the process of vacuum sensor measurement, the most important aspect is the amplification of the ion current. However, the collected ion current signal is weak, falling within the picoampere (pA) range. Therefore, amplifying the picoampere (pA) current is crucial. In ion detection, ion current amplification devices are typically used to amplify the weak ion current signal for accurate detection. For example, air ion detector signal amplifier calibration devices provide various current signals of different magnitudes to calibrate the air ion detector signal amplifier. Ion current amplification devices can amplify the ion current signal in similar detection mechanisms, thereby ensuring the reliability and accuracy of the measurement data.

[0003] Existing ion current amplification devices consist of a programmable ion current amplifier, an integrating network, and a main operational amplifier. Their primary function is to amplify the weak ion current obtained from the collector of an analog tube and send it to an A / D converter. However, the voltage returned by existing ion current amplification devices is extremely small and susceptible to interference, often resulting in the inability to detect the weak ion current collected during vacuum measurements. Therefore, there is an urgent need for an ion current detection device capable of generating a stable voltage that is less susceptible to interference. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of existing ion flow amplification devices and to provide a picoampere-level ion flow detection device.

[0005] The objective of this utility model is achieved through the following technical solution:

[0006] A picoampere-level ion current detection device is provided, comprising an ion current amplification circuit, a main operational amplifier circuit, an analog-to-digital converter circuit, and a microcontroller connected in sequence; the ion current amplification circuit includes a detection circuit, a first-stage operational amplifier circuit, and a second-stage operational amplifier circuit connected in sequence; the analog-to-digital converter circuit includes an analog-to-digital converter and an optocoupler connected in sequence.

[0007] In some embodiments, diodes are connected to the input terminals of the first-stage operational amplifier circuit and the second-stage operational amplifier circuit, respectively.

[0008] In some embodiments, the detection circuit includes two detection resistors and a switching switch for switching the detection resistors.

[0009] In some embodiments, a capacitor is connected in parallel with the detection resistor.

[0010] In some embodiments, the two detection resistors include a 1.01MΩ detection resistor and a 10KΩ detection resistor, and the switching switch is a photoelectric relay or a mechanical relay.

[0011] In some embodiments, the output terminal of the main operational amplifier circuit is provided with an overvoltage protection circuit.

[0012] In some embodiments, a FET input operational amplifier circuit is provided between the analog-to-digital converter and the optocoupler.

[0013] In some embodiments, the amplifier in the first-stage operational amplifier circuit is a CA3140 or a TLC2652, and the amplifier in the second-stage operational amplifier circuit is a HA17741.

[0014] In some embodiments, the amplifier in the main operational amplifier circuit is model HA17741.

[0015] In some embodiments, the analog-to-digital converter is an LM331, the optocoupler is a 6N137, and the microcontroller includes an X5045 programmable circuit.

[0016] It should be further noted that the technical features corresponding to the above options can be combined or substituted to form new technical solutions.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] (1) This utility model amplifies the acquired signal through multi-stage operational amplifiers and enhances the anti-interference capability by setting up an optocoupler to achieve multi-stage operational amplifiers, multiple filtering, signal noise suppression and anti-interference of the acquired signal, improves the useful signal in the ion flow, effectively limits the noise signal, improves the signal-to-noise ratio, and enables the weak ion flow collected during vacuum measurement to be identified. Finally, it provides a high-precision operational amplifier with low offset, high gain, strong common-mode rejection capability, fast response, low drift and stable performance, and outputs a real, reliable, stable and easy-to-process electrical signal to realize the precise detection function of low-power picoampere level weak signals.

[0019] (2) In one example, the analog-to-digital converter circuit uses high-resolution analog-to-digital conversion technology to segment the signal with high precision, thereby improving the accuracy of the measurement.

[0020] (3) In one example, diodes are connected to the input terminals of the first-stage op-amp circuit and the second-stage op-amp circuit respectively. When the circuit is working normally, the input signal amplitude is very small, so the diodes do not conduct. If the input signal is large, the diodes conduct, so as not to affect the normal operation of the circuit and prevent the amplifier from being damaged due to excessive input signal amplitude.

[0021] (4) In one example, a capacitor is connected in parallel with the detection resistor. Because the circuit gain is high, a capacitor is connected in parallel with the detection resistor to prevent high-frequency oscillation. Because its capacitance is small, it has a very small impact on the signal amplification factor.

[0022] (5) In one example, the output terminal of the main operational amplifier circuit is provided with an overvoltage protection circuit to prevent the output overvoltage from causing the subsequent circuits to malfunction.

[0023] (6) In one example, the range is extended by placing a FET input op-amp circuit between the analog-to-digital converter and the optocoupler. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a picoampere-level ion current detection device according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of an ion current amplification circuit shown in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of an analog-to-digital converter circuit shown in an embodiment of the present invention;

[0027] Figure 4 This is a detailed circuit diagram of the ion current amplification circuit shown in an embodiment of the present invention;

[0028] Figure 5 The following is a detailed circuit diagram of the main operational amplifier circuit and the analog-to-digital converter circuit shown in an embodiment of this utility model. Detailed Implementation

[0029] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0030] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0031] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0032] Reference Figures 1-3 In one exemplary embodiment, a picoampere-level ion current detection device is provided, comprising an ion current amplification circuit, a main operational amplifier circuit, an analog-to-digital converter circuit, and a microcontroller connected in sequence; the ion current amplification circuit includes a detection circuit, a first-stage operational amplifier circuit, and a second-stage operational amplifier circuit connected in sequence; the analog-to-digital converter circuit includes an analog-to-digital converter and an optocoupler connected in sequence.

[0033] The schematic diagram of the ion current amplifier circuit is as follows: Figure 4 As shown, the schematic diagram of the analog-to-digital converter circuit is as follows: Figure 5 As shown, an operational amplifier CA3140 is used as the first-stage op-amp. The stable, interference-resistant voltage generated by the first-stage op-amp of CA3140 is insufficient for stable acquisition and use. Therefore, after passing through the CA3140 output voltage, it passes through a second-stage op-amp HA17741. The weak ion current signal is amplified by the programmable ion current amplifier and then processed through a series of steps before being sent to a display or recorder for display or recording.

[0034] Furthermore, to prevent damage to the amplifier due to excessively large input signal amplitude, protective diodes were added at the input terminals, such as... Figure 4 In this circuit, diodes are connected to the input terminals of both the first-stage and second-stage operational amplifier circuits. Since the input signal amplitude is very small during normal operation, the diodes do not conduct. If the input signal is large, the diodes conduct, thus not affecting the normal operation of the circuit. Furthermore, the circuit has a high gain; to prevent high-frequency oscillations, a capacitor is connected in parallel with the sensing resistor. Because its capacitance is small, its impact on the signal amplification factor is also very small.

[0035] The main function of the main operational amplifier circuit is to amplify the signal output from the programmable ion current amplifier. The design should consider the variable β of this operational amplifier stage. To prevent output overvoltage from causing subsequent circuits to malfunction, an overvoltage protection circuit composed of Zener diodes is added.

[0036] like Figure 4As shown, the sensing resistor has two ranges: 1.01MΩ (R52 in the diagram) when IE is 0.25mA, and 10KΩ (R51 in the diagram) when IE is 0.025mA. Several options are available for the changeover switch: mechanical relays, semiconductor photoresistors, and reed relays. General multiplexers are unsuitable due to excessive leakage current. In typical applications, photoresistors and mechanical relays are good choices; considering power consumption and size, photoresistors are the optimal choice. In other examples, a sensitive mechanical relay (power consumption approximately 140mW) can also meet the power consumption requirements, such as the Panasonic TX2-24V.

[0037] In other examples, considering the leakage current characteristics of the devices, the first-stage amplifier can also be the chopper-stabilized high-precision operational amplifier TLC2652. The TLC2652 has a typical bias current of 2pA and a typical offset voltage of 0.6uV, exhibiting excellent static performance and slightly lower noise levels, making it suitable as the first stage amplification for the front-end input. The circuit achieves approximately a 6x amplification factor, and with a 1.01MΩ sense resistor, it can convert and amplify a current of 3.75*10⁻¹⁰A to approximately 2.2mV under extreme vacuum.

[0038] The voltage amplified by the ion current amplifier circuit is sequentially converted into a digital signal by the main operational amplifier circuit and the analog-to-digital converter circuit, and then sent to the microprocessor / microcontroller for processing. For example... Figure 5 As shown, the main operational amplifier circuit includes the amplifier HA17741, and the analog-to-digital conversion circuit includes the analog-to-digital converter LM331 and the optocoupler 6N137, etc.

[0039] Since the output of the main operational amplifier circuit cannot be accepted by the subsequent microprocessor, an A / D conversion is necessary. In this circuit structure, a FET input operational amplifier is added to expand the measurement range. The reference current IR is set by the resistor connected to pin 2 of the LM331. Since the internal reference voltage is 1.9V, IR = 1.9V / R63 + W10, typically set to 100-150uA. Additionally, the average current IO at pin 1 of the current switch output is equal to the input current IN. Pulse width: T = 1.1 × R67 × C18; Average current: IO = IR × 1.1 × R67 × C18; that is, IO is proportional to the frequency FO. Therefore:

[0040] FO=IO / (IR×1.1×R67×C18)=(-Un / R59)×(R63+W10) / (2.09×R67×C18).

[0041] Therefore, adjusting the potentiometer can change the frequency of the output pulse. The LM331's output is open-collector, and a pull-up resistor R66 must be connected when driving logic circuits.

[0042] The 6N137 optocoupler serves as a channel isolation device, enhancing its anti-interference capability. The 6N137 is a high-speed optocoupler for single-channel applications, featuring temperature, current, and voltage compensation, high input-output isolation, LSTTL / TTL compatibility, high speed (typically 10MBd), and a minimum input current of 5mA. During the design process, a 0.1uF decoupling capacitor (tantalum capacitor) is connected next to the power supply pin of the 6N137 optocoupler to further enhance its anti-interference capability.

[0043] Ultimately, the collected frequency signals undergo computation, curve calibration, and data acquisition from an external storage device via the microcontroller's internal software. This requires a large storage capacity, which is achieved using the X5045 programmable circuit. Thus, the weak signal from the picoampere-level particle stream is transformed into a recognizable digital signal through the aforementioned circuitry, enabling precise detection of low-power picoampere-level weak signals.

[0044] The above detailed embodiments are a detailed description of the present utility model. It should not be considered that the specific embodiments of the present utility model are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present utility model, and all of these should be considered to fall within the protection scope of the present utility model.

Claims

1. A picoampere-level ion current detection device, characterized in that, It includes an ion current amplification circuit, a main operational amplifier circuit, an analog-to-digital converter circuit, and a microcontroller connected in sequence; the ion current amplification circuit includes a detection circuit, a first-stage operational amplifier circuit, and a second-stage operational amplifier circuit connected in sequence; the analog-to-digital converter circuit includes an analog-to-digital converter and an optocoupler connected in sequence.

2. The picoampere-level ion current detection device according to claim 1, characterized in that, Diodes are connected to the input terminals of the first-stage operational amplifier circuit and the second-stage operational amplifier circuit, respectively.

3. The picoampere-level ion current detection device according to claim 1, characterized in that, The detection circuit includes two detection resistors and a switch for switching the detection resistors.

4. The picoampere-level ion current detection device according to claim 3, characterized in that, A capacitor is connected in parallel with the detection resistor.

5. The picoampere-level ion current detection device according to claim 3, characterized in that, The two detection resistors include a 1.01MΩ detection resistor and a 10KΩ detection resistor, and the switching switch is a photoelectric relay or a mechanical relay.

6. The picoampere-level ion current detection device according to claim 1, characterized in that, The output terminal of the main operational amplifier circuit is equipped with an overvoltage protection circuit.

7. The picoampere-level ion current detection device according to claim 1, characterized in that, An FET input operational amplifier circuit is provided between the analog-to-digital converter and the optocoupler.

8. The picoampere-level ion current detection device according to claim 1, characterized in that, The amplifier in the first-stage operational amplifier circuit is either CA3140 or TLC2652, and the amplifier in the second-stage operational amplifier circuit is HA17741.

9. The picoampere-level ion current detection device according to claim 1, characterized in that, The amplifier in the main operational amplifier circuit is model HA17741.

10. The picoampere-level ion current detection device according to claim 1, characterized in that, The analog-to-digital converter is an LM331, the optocoupler is a 6N137, and the microcontroller includes an X5045 programmable circuit.

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