Mass spectrometer electrometer based on capacitance integrator

Abstract

The invention discloses a mass spectrometer electrometer based on a capacitance integrator, and belongs to the technical field of electrometers. Comprising a capacitance integrator, the capacitance integrator is connected with a voltage holding circuit, the voltage holding circuit is connected with an acquisition control circuit and an amplification circuit, and the amplification circuit is connected with the acquisition control circuit; and the acquisition control circuit controls electric signals input into the capacitance integrator, the voltage holding circuit and the amplifying circuit through an I / V conversion control method, so that I / V conversion is completed. The capacitance integration is used for completing I / V conversion, the problem of high-resistance forbidding can be solved, meanwhile, compared with high-resistance conversion, the capacitance integration is adopted, the temperature stability of the electrometer is improved, and noise is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrometers, and in particular to a mass spectrometer electrometer based on a capacitive integrator. Background Art

[0002] A mass spectrometer electrometer is mainly a device for measuring tiny weak electrical signals. It amplifies a weak current through a high resistance and converts it into a voltage signal that can be collected. Since the weak electrical signal output of a mass spectrometer can reach the fA level, an ordinary resistance value cannot generate a voltage signal for collection through I / V conversion. Therefore, a high resistance (above 100 GΩ) is required to convert the current signal into a voltage signal. Currently, all high resistances that meet the requirements of resistance value > 100 GΩ, accuracy error of 5%, and temperature drift of 50 ppm / °C rely entirely on imported foreign devices, and the current import channels have been restricted. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a mass spectrometer electrometer based on a capacitive integrator.

[0004] The purpose of the present invention is achieved through the following technical solutions: A mass spectrometer electrometer based on a capacitive integrator is connected to an acquisition control circuit and includes a capacitive integrator. The capacitive integrator is connected to a voltage holding circuit. The voltage holding circuit is connected to the acquisition control circuit and an amplification circuit. The amplification circuit is connected to the acquisition control circuit. The acquisition control circuit controls the electrical signals input to the capacitive integrator, the voltage holding circuit, and the amplification circuit through an I / V conversion control method, thereby completing the I / V conversion.

[0005] Preferably, the voltage holding circuit includes a relay module K1 integrated with three relays whose impedances reach a preset level.

[0006] Preferably, the capacitive integrator includes an operational amplifier U1A with an input resistance greater than a preset resistance value and a capacitor C1. The negative input terminal of the operational amplifier U1A is connected to the 15th pin, the 5th pin of the relay module K1, and the first end of the capacitor C1. The positive input terminal of the operational amplifier U1A is connected to the ground GND. The positive and negative power supply terminals of the operational amplifier U1A are respectively connected to the positive and negative power supplies. The output terminal of the operational amplifier U1A is connected to the 12th pin, the 4th pin of the relay module K1, and the second end of the capacitor C1.

[0007] Preferably, the amplifying circuit includes operational amplifier U2A, operational amplifier U3A, resistor R3, resistor R4, resistor R5, resistor R6, and resistor R7; the positive input terminal of operational amplifier U2A is connected to pin 14 of relay module K1, the negative input terminal of operational amplifier U2A is connected to the output terminal of operational amplifier U2A and the first terminal of resistor R5, and the positive and negative power supply terminals of operational amplifier U2A are connected to the positive and negative power supplies; the second terminal of resistor R5 is connected to the first terminal of resistor R4 and the negative input terminal of operational amplifier U3A; the positive input terminal of operational amplifier U3A is connected to the first terminal of resistor R6, the output terminal of operational amplifier U3A is connected to the first terminal of resistor R3 and the second terminal of resistor R4, and the positive and negative power supply terminals of operational amplifier U3A are connected to the positive and negative power supplies; the second terminal of resistor R6 is connected to ground GND; the second terminal of resistor R3 is connected to the first terminal of resistor R7 and the subsequent circuit; the second terminal of resistor R7 is connected to ground GND.

[0008] Preferably, the I / V conversion control method includes the following steps: The acquisition control circuit sets pin 10 of relay module K1 to high level through the Hold-Control signal, thereby controlling the conduction between pin 2 and pin 15 of relay module K1; the current signal Iin is input to pin 2 of relay module K1 to charge capacitor C1. At the same time, the acquisition control circuit sets pin 9 of relay module K1 to low level through the Reset-Control signal, controlling the non-conduction between pin 4 and pin 5 of relay module K1, thereby closing the discharge channel of the charge of capacitor C1. The input current signal Iin will integrate on capacitor C1. Within a certain time dt, Q = I×dt, and voltage U1 = Q / C, where Q is the accumulated charge amount on capacitor C1, I is the current magnitude of the input current signal Iin, and C is the capacitance value of capacitor C1; at this time, the acquisition control circuit sets pin 11 of relay module K1 to high level through the SEL-Control signal, thereby controlling the conduction between pin 12 and pin 14 of relay module K1, outputting voltage U1 to pin 12 of relay module K1 and transmitting it to pin 14 to be amplified by the amplifying circuit, and finally the acquisition control circuit acquires the finally converted voltage.

[0009] Preferably, after the acquisition control circuit acquires the finally converted voltage, it controls the conduction between pin 4 and pin 5 of relay module K1 to release the charge signal on capacitor C1 and reduce the output voltage to 0.

[0010] Preferably, when charging capacitor C1, the acquisition control circuit controls the conduction between pin 5 and pin 15 of relay module K1; the current signal Iin charges on capacitor C1.

[0011] Preferably, the preset level is of the TΩ level.

[0012] Preferably, the capacitor C1 is a polyester capacitor.

[0013] The beneficial effects of the present invention are as follows: 1) Using a capacitor integrator to complete I / V conversion can solve the problem of high-resistance sales bans. At the same time, using a capacitor integrator improves the temperature stability of the electrometer and reduces noise compared to using a high-resistance transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic block diagram of the electrometer of a mass spectrometer based on a capacitor integrator; Figure 2 is a schematic circuit diagram of the electrometer of a mass spectrometer based on a capacitor integrator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] Hereinafter, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0016] Refer to Figure 1 - Figure 2 , the present invention provides a technical solution: an electrometer of a mass spectrometer based on a capacitor integrator, connected to an acquisition control circuit, including a capacitor integrator, the capacitor integrator is connected to a voltage holding circuit, the voltage holding circuit is connected to the acquisition control circuit and an amplification circuit, and the amplification circuit is connected to the acquisition control circuit; the acquisition control circuit controls the electrical signals input to the capacitor integrator, the voltage holding circuit and the amplification circuit through an I / V conversion control method, thereby completing the I / V conversion.

[0017] In this embodiment, the acquisition control circuit includes a single-chip microcomputer for signal acquisition and voltage holding circuit control. In order to reduce the dependence of the electrometer of the mass spectrometer on high-performance high-resistance, a form of integrating a capacitor for minute weak current is proposed to measure the magnitude of the minute weak current, completing the design of I / V conversion for weak current signals from passing through a high-resistance to using capacitor integration, and solving the situation of dependence on banned high-resistance. At the same time, capacitor integration has significant advantages over high-resistance transformation, such as low noise and good temperature stability.

[0018] In some embodiments, the voltage holding circuit includes a relay module K1 integrating three relays with impedances reaching a preset level.

[0019] In this embodiment, the voltage holding circuit includes three relays with impedances capable of reaching the TΩ level, and the switches of the relays are controlled by the single-chip microcomputer inside the acquisition control circuit.

[0020] In some embodiments, the capacitive integrator includes an operational amplifier U1A with an input resistance greater than a preset value and a capacitor C1; the negative input terminal of the operational amplifier U1A is connected to the 15th, 5th pins of the relay module K1 and the first end of the capacitor C1, the positive input terminal of the operational amplifier U1A is connected to the ground GND, the positive and negative power supply terminals of the operational amplifier U1A are respectively connected to the positive and negative power supplies, and the output terminal of the operational amplifier U1A is connected to the 12th, 4th pins of the relay module K1 and the second end of the capacitor C1.

[0021] In this embodiment, the capacitive integrator includes an operational amplifier with an extremely high input resistance and a polyester capacitor with high precision and good temperature stability.

[0022] In some embodiments, the amplification circuit includes operational amplifiers U2A, U3A, resistors R3, R4, R5, R6, R7; the positive input terminal of the operational amplifier U2A is connected to the 14th pin of the relay module K1, the negative input terminal of the operational amplifier U2A is connected to the output terminal of the operational amplifier U2A and the first end of the resistor R5, and the positive and negative power supply terminals of the operational amplifier U2A are connected to the positive and negative power supplies; the second end of the resistor R5 is connected to the first end of the resistor R4 and the negative input terminal of the operational amplifier U3A; the positive input terminal of the operational amplifier U3A is connected to the first end of the resistor R6, the output terminal of the operational amplifier U3A is connected to the first end of the resistor R3 and the second end of the resistor R4, and the positive and negative power supply terminals of the operational amplifier U3A are connected to the positive and negative power supplies; the second end of the resistor R6 is connected to the ground GND; the second end of the resistor R3 is connected to the first end of the resistor R7 and the subsequent circuit; the second end of the resistor R7 is connected to the ground GND.

[0023] In this embodiment, the amplification circuit includes two operational amplifiers for waveform amplification. As Figure 2 shown, Vout is the amplified output voltage, which is output to the subsequent circuit.

[0024] In some embodiments, the I / V conversion control method includes the following steps: The acquisition control circuit sets the 10th pin of the relay module K1 to a high level through the Hold-Control signal, thereby controlling the conduction between the 2nd and 15th pins of the relay module K1; inputs the current signal Iin to the 2nd pin of the relay module K1 to charge the capacitor C1, and at the same time, the acquisition control circuit sets the 9th pin of the relay module K1 to a low level through the Reset-Control signal, controls the non-conduction between the 4th and 5th pins of the relay module K1, thereby closing the charge discharge channel of the capacitor C1; The input current signal Iin will be integrated on capacitor C1. Within a certain time dt, Q = I×dt, and voltage U1 = Q / C, where Q is the amount of charge accumulated on capacitor C1, I is the magnitude of the input current signal Iin, and C is the capacitance value of capacitor C1. At this time, the acquisition control circuit sets pin 11 of relay module K1 to high level through the SEL-Control signal, thereby controlling pins 12 and 14 of relay module K1 to conduct, outputting voltage U1 to pin 12 of relay module K1 and transmitting it to pin 14 to be amplified by the amplifier circuit, and finally the acquisition control circuit acquires the finally converted voltage.

[0025] In this embodiment, an fA-level current source flows in through Iin. To allow current Iin to charge capacitor C1, it is necessary to ensure that the channel from the current source Iin to capacitor C1 is conducting, that is, pins 2 and 15 of K1 are conducting, and at the same time, it is necessary to close the charge discharge channel of C1, that is, pins 4 and 5 of K1 are not conducting. The acquisition control circuit controls pin 10 of Hold-Control input to be at high level to ensure that pins 2 and 15 are conducting, and at the same time controls pin 9 of Reset-Control signal input to be at low level to ensure that pins 4 and 5 are not conducting. The input current Iin will be integrated on capacitor C1. Within a certain time dt, Q = I×dt, and voltage U1 = Q / C = (I×dt) / C. To ensure that voltage U1 is acquired by the acquisition control circuit, it is necessary to ensure that the voltage value on C1 is transmitted from pin 12 of K1 to pin 14 of K1 for the backend amplifier to amplify. The acquisition control circuit controls pin 11 of K1 to be at high level, pins 12 and 14 of K1 are conducting, and the voltage value on C1 is amplified by the amplifier circuit and acquired by the acquisition control circuit. When the acquisition control circuit completes the acquisition, it is necessary to release the charge signal on C1, and it is necessary for pins 4 and 5 of K1 to conduct. The acquisition control circuit controls Reset-Control of pin 9 of K1 to be at high level, pins 4 and 5 of K1 are conducting, and at this time the charge on capacitor C1 is released, and the output voltage will be zero.

[0026] For different elements, the output current Iin is different, resulting in different amounts of charge accumulated on the capacitor in the same time, and further resulting in different output voltages. Therefore, using a capacitive integration type electrometer can also complete the function of a resistive I / V conversion electrometer.

[0027] In some embodiments, after the acquisition control circuit acquires the finally converted voltage, it controls pins 4 and 5 of relay module K1 to conduct, and releases the charge signal on capacitor C1 to reduce the output voltage to 0.

[0028] In some embodiments, when charging capacitor C1, the acquisition control circuit controls pins 5 and 15 of relay module K1 to conduct; the current signal Iin charges on capacitor C1.

[0029] In this embodiment, the current signal Iin flows into pin 2 of the relay K1. The connection and disconnection between pin 2 and pin 15 of K1 are controlled by the Hold-Control of pin 10 of K1, and the connection and disconnection between pin 4 and pin 5 of K1 are controlled by the Reset-Control of pin 9 of K1. When it is necessary to charge the capacitor C1, the Hold-Control of pin 10 of K1 needs to be set to a high level through the centralized control circuit. At this time, pin 5 and pin 15 of K1 are conducted, and the current signal Iin charges on the capacitor C1. At the same time, the 9th pin of K1 is set to a low level through the centralized control circuit, and pin 4 and pin 5 of K1 are disconnected, so that the charge signal on the capacitor is not released. The connection and disconnection between pin 12 and pin 14 of K1 are controlled by the 11th pin of K1. When it is necessary to collect the voltage value on C1 by the acquisition control circuit, the Self-Control of pin 11 of K1 needs to be set to a high level by the acquisition control circuit. When the acquisition control circuit completes the acquisition of the voltage value on C1, it is necessary to discharge the capacitor C1. The Reset-Control of pin 9 of K1 needs to be set to a high level by the acquisition control circuit, and pin 4 and pin 5 of K1 are conducted, and the charge signal on C1 is released, and the voltage value is zero.

[0030] In some embodiments, the preset level is of the TΩ level.

[0031] In some embodiments, the capacitor C1 is a polyester capacitor.

[0032] The above are only the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments. Instead, it can be used in various other combinations, modifications, and environments, and can be changed within the scope of the concept described herein through the above teachings or the techniques or knowledge in related fields. And any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A mass spectrometer electrometer based on a capacitance integrator, connected to an acquisition control circuit, characterized in that: It includes a capacitive integrator which is connected to a voltage holding circuit. The voltage holding circuit is connected to an acquisition control circuit and an amplification circuit, and the amplification circuit is connected to the acquisition control circuit. The acquisition control circuit controls the electrical signals input to the capacitive integrator, the voltage holding circuit and the amplification circuit through an I / V conversion control method, thereby completing the I / V conversion.

2. The electrometer of the mass spectrometer based on a capacitive integrator according to claim 1, characterized in that: The voltage holding circuit includes a relay module K1 integrating three relays with impedances reaching a preset level.

3. The electrometer of the mass spectrometer based on a capacitive integrator according to claim 2, characterized in that: The capacitive integrator includes an operational amplifier U1A with an input resistance greater than a preset value and a capacitor C1. The negative input terminal of the operational amplifier U1A is connected to the 15th pin, the 5th pin of the relay module K1 and the first end of the capacitor C1. The positive input terminal of the operational amplifier U1A is connected to the ground GND. The positive and negative power supply terminals of the operational amplifier U1A are respectively connected to the positive and negative power supplies. The output terminal of the operational amplifier U1A is connected to the 12th pin, the 4th pin of the relay module K1 and the second end of the capacitor C1.

4. The electrometer of a mass spectrometer based on a capacitance integrator according to claim 3, characterized in that: The amplification circuit includes an operational amplifier U2A, an operational amplifier U3A, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7. The positive input terminal of the operational amplifier U2A is connected to the 14th pin of the relay module K1. The negative input terminal of the operational amplifier U2A is connected to the output terminal of the operational amplifier U2A and the first end of the resistor R5. The positive and negative power supply terminals of the operational amplifier U2A are connected to the positive and negative power supplies. The second end of the resistor R5 is connected to the first end of the resistor R4 and the negative input terminal of the operational amplifier U3A. The positive input terminal of the operational amplifier U3A is connected to the first end of the resistor R6. The output terminal of the operational amplifier U3A is connected to the first end of the resistor R3 and the second end of the resistor R4. The positive and negative power supply terminals of the operational amplifier U3A are connected to the positive and negative power supplies. The second end of the resistor R6 is connected to the ground GND. The second end of the resistor R3 is connected to the first end of the resistor R7 and the subsequent circuit. The second end of the resistor R7 is connected to the ground GND.

5. The electrometer of a mass spectrometer based on a capacitive integrator according to claim 3, characterized in that: The I / V conversion control method includes the following steps: The acquisition control circuit sets the 10th pin of the relay module K1 to a high level through a Hold-Control signal, thereby controlling the conduction between the 2nd pin and the 15th pin of the relay module K1. The current signal Iin is input to the 2nd pin of the relay module K1 to charge the capacitor C1. At the same time, the acquisition control circuit sets the 9th pin of the relay module K1 to a low level through a Reset-Control signal, controlling the non-conduction between the 4th pin and the 5th pin of the relay module K1, thereby closing the discharge charge channel of the capacitor C1. The input current signal Iin will be integrated on capacitor C1. Within a certain time dt, Q = I×dt, and voltage U1 = Q / C, where Q is the amount of charge accumulated on capacitor C1, I is the magnitude of the input current signal Iin, and C is the capacitance value of capacitor C1. At this time, the acquisition control circuit sets the 11th pin of relay module K1 to high level through the SEL-Control signal, thereby controlling the conduction of the 12th and 14th pins of relay module K1, outputting voltage U1 to the 12th pin of relay module K1 and transmitting it to the 14th pin to be amplified by the amplifier circuit, and finally the acquisition control circuit acquires the finally converted voltage.

6. The electrometer of a mass spectrometer based on a capacitive integrator according to claim 5, wherein: After the acquisition control circuit acquires the finally converted voltage, it controls the conduction of the 4th and 5th pins of relay module K1 to release the charge signal on capacitor C1 and reduce the output voltage to 0.

7. The electrometer of a mass spectrometer based on a capacitive integrator according to claim 5, characterized in that: When charging capacitor C1, the acquisition control circuit controls the conduction of the 5th and 15th pins of relay module K1; the current signal Iin charges on capacitor C1.

8. The electrometer of a mass spectrometer based on a capacitance integrator according to claim 2, wherein: The preset level is of the TΩ level.

9. The electrometer of a mass spectrometer based on a capacitance integrator according to any one of claims 3-7, characterized in that: The capacitor C1 is a polyester capacitor.

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