Gating PMT-LIBS signal high-speed acquisition system based on AD9226

Abstract

The invention discloses an AD9226-based gated PMT-LIBS signal high-speed acquisition system, which has an acquisition frequency of 7.6 MHz. The main working process is as follows: a user sends an instruction through upper computer software, a serial port communication module sends a command to a time sequence controller, the time sequence controller sends a pulse to a laser device to generate a laser ablation sample to generate plasma, and the laser ablation sample generates a pulse signal; after a certain time delay, the time sequence controller sends a pulse to trigger a gate PMT to collect an LIBS spectrum and trigger a micro-processing chip STM32H750V8T6 chip (hereinafter referred to as H750) of an Italian semiconductor company to work, and the H750 sends a time sequence to the AD9226 chip to control the AD9226 chip to collect a gained PMT signal and receive collected 12-bit data through an IO port. And the H750 receives the data, converts the data through program operation, and sends the data to the upper computer software through the serial port communication module and stores the data, so that the collection work is completed. In order to solve the problem that PMT signals are difficult to collect, high-speed collection of the PMT signals is achieved through the AD9226 high-speed collection chip, and actual application of the gating PMT-LIBS technology in the field of water quality heavy metal detection is promoted.

Description

Technical field:

[0001] The present invention relates to the cross-field of spectrum analysis technology and photoelectric conversion, and in particular to a PMT signal acquisition method. Background technology:

[0002] Laser induced breakdown spectroscopy (LIBS) uses laser ablation to generate plasma on the sample surface, and collects and analyzes the spectrum emitted by the plasma to achieve qualitative and quantitative analysis of the elements in the sample to be tested.

[0003] PMT (photomultiplier tube) is a detection device that can convert weak light signals into electrical signals. It has extremely high sensitivity and ultra-fast time response, and has irreplaceable advantages in detecting weak spectral signals.

[0004] AD9226 is a single-channel high-speed acquisition chip with a maximum sampling rate of 65MHz and a sampling resolution of 12 bits. It achieves accurate and distortion-free acquisition of 12-bit data by using a multi-stage differential pipeline structure with error correction logic. Summary of the invention:

[0005] Purpose of the invention: The PMT signal acquisition system mainly includes a digital oscilloscope, a gate integrator averager, a PCle8512 acquisition card, etc. However, the above acquisition systems face the problems of high cost, large size, difficult integration, and complex operation. Therefore, the present invention provides a PMT signal acquisition system and acquisition method based on embedded technology to realize the acquisition and storage of PMT signals, which is convenient for subsequent processing.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a gated PMT-LIBS signal high-speed acquisition system based on AD9226. Specifically, it includes the following solutions:

[0007] A gated PMT-LIBS signal high-speed acquisition system based on AD9226 is mainly divided into hardware circuit design based on H750 and AD9226 and host computer software development based on Python.

[0008] The H750 and AD9226 hardware circuits include: a power input module, an analog-to-digital conversion (AD) circuit, a serial communication module circuit, and a PMT monitoring circuit.

[0009] The Python-based software design includes: software development environment, serial communication submodule, and host computer user interaction interface.

[0010] Furthermore, the power input module can be externally connected to 3.3V and 5V voltage regulators, and a number of capacitors can be used to improve voltage fluctuations and noise interference, thereby improving circuit stability.

[0011] Furthermore, the core of the analog-to-digital conversion (AD) circuit is an AD9226 chip, which converts the continuous PMT signal into a 12-bit digital quantity.

[0012] Furthermore, the serial communication module circuit is responsible for data transmission between H750 and the host computer software.

[0013] Furthermore, the PMT monitoring circuit is used to monitor the PMT gain voltage and working status.

[0014] Furthermore, the software development environment is Python, and the host computer user interaction interface is completed using Qt Designer.

[0015] The invention discloses a method for high-speed acquisition of PMT signals, which can realize an acquisition frequency of 7.6 MHz. The main working process is as follows: a user edits a host computer parameter and sends the parameter to a timing controller through a serial communication module, and executes a waiting command; the timing controller sends a pulse to a laser to trigger laser ablation of a sample to generate plasma; the timing controller delays for a certain period of time and respectively triggers a gated PMT to acquire a plasma spectrum and generate a PMT signal, and triggers H750 to send a timing signal to AD9226 for analog-to-digital conversion to generate a 12-bit digital signal; the H750 receives the 12-bit digital signal and sends it to the host computer through a serial communication module after program conversion and calculation; the host computer receives the data and saves it in a csv file of a specified path after verification, thereby realizing one-time gated PMT-LIBS signal acquisition. Description of the drawings:

[0016] Figure 1 It is a structural block diagram of the overall system design of the present invention.

[0017] Figure 2 It is the user interaction interface of the host computer software.

[0018] Figure 3 This is a practical example flow chart of a PMT signal high-speed acquisition system applied to a LIBS analysis system provided by the present invention.

[0019] Figure 4 The present invention is actually applied to the quantitative detection results of the gated PMT-LIBS analysis system for the heavy metals Pb and Cr in water quality. (a) is the quantitative fitting curve of the Pb element, and (b) is the quantitative fitting curve of the Cr element. Specific implementation method:

[0020] The present invention will be described in detail below with reference to the accompanying drawings and through preferred embodiments of the present invention.

[0021] The present invention is a gated PMT-LIBS signal high-speed acquisition system based on AD9226. The following describes in detail the implementation process of the present invention applied to the quantitative detection of heavy metals Pb and Cr in water using the LIBS technology.

[0022] The water sample was dropped onto the Zn substrate, with a single drop volume of 50 μL, and evaporated on a heating table at 70 °C to achieve liquid-solid conversion.

[0023] Connect the high-speed acquisition module to the timing controller, voltage regulator and gated PMT module as required.

[0024] Set the laser external trigger energy to 100mJ and the acquisition delay to 3μs to collect single-point water quality samples. The specific process is:

[0025] The host computer system sends commands to the timing controller through the serial communication module. The timing controller immediately sends a pulse signal to the laser. The laser responds to the pulse and emits laser to ablate the sample surface to generate plasma. The host computer interface is as follows: Figure 2 shown.

[0026] After a certain delay, the timing controller sends delayed pulse signal 1 and delayed pulse signal 2 to PMT and H750. After receiving the signal, PMT passes through the filter of the corresponding element, collects the spectral signal of the corresponding wavelength and converts it into an electrical signal. After passing through the gain module, the electrical signal is input into the analog signal input end of the high-speed acquisition system through the SMA port.

[0027] H750 responds to the delayed pulse signal 2 and sends a pulse signal to the CLK port of AD9226. The number of times it sends is determined by the number of acquisitions required by the user.

[0028] Each time AD9226 receives a pulse signal, it performs an AD conversion and sends the sampled value to the IO port of H750 via D0-D11. H750 reads the IO port data and converts and calculates it to obtain the corresponding signal amplitude.

[0029] After completing all acquisition times, H750 sends the acquired signal amplitude to the host computer software through serial port communication.

[0030] The host computer detects the received data and determines whether the data is valid through the communication protocol, generates a csv file in the specified file path and saves the valid data.

[0031] The obtained signal amplitude is integrated at 3.12-9.88μs and can be converted into the spectral intensity of the corresponding spectral line, so as to quantitatively fit it.

[0032] The flow chart of this embodiment is as follows Figure 3 As shown in the figure, the quantitative fitting results for Pb and Cr are as follows Figure 4 As shown in the figure, in the quantitative detection of heavy metals Pb and Cr in aqueous solution by LIBS, the quantitative fitting degrees are 0.989 and 0.977 respectively, and the relative standard deviations RSD are 2.84% and 7.17% respectively.

[0033] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A gated PMT-LIBS signal high-speed acquisition system based on AD9226, characterized in that: It mainly includes hardware circuit design based on H750 and AD9226 and host computer software development based on Python: the H750 hardware circuit includes: power input module, analog-to-digital conversion (AD) circuit, serial communication module circuit, PMT monitoring circuit, and the host computer software development based on Python includes: software development environment, serial communication sub-module, and host computer user interaction interface.

2. According to the hardware circuit design based on H750 in claim 1, the power input module selects an external voltage regulator with a terminal of 2.54mm pin spacing to power the circuit, and uses several 104 capacitors for filtering and rectification; the main component of the analog-to-digital conversion (AD) circuit is the AD9226 chip, which is controlled by sending timing pulses through H750 to convert continuous analog quantities into 12-bit digital quantities and received and converted by the IO port of H750; the serial communication module is mainly responsible for data transmission between H750 and the host computer, and the PMT monitoring circuit is mainly responsible for monitoring the PMT gain and working status.

3. According to the Python-based host computer software development described in claim 1, the host computer user interaction interface is designed using QtDesigner, the software development environment is Python, and the communication submodule mainly realizes the data transmission function between the control timing controller and H750.

4. According to the high-speed acquisition system of claim 1, its main working process is: the user issues instructions by editing the host computer data, the serial port communication sends instructions to the timing controller, and executes the waiting command, the timing controller sends pulses to the laser to trigger the laser ablation sample to generate plasma, and after a certain delay, the gated PMT is triggered to collect the plasma spectrum and generate a PMT signal, and the H750 is triggered to send a timing signal to AD9226 for analog-to-digital conversion to generate a 12-bit digital signal, the H750 receives the 12-bit digital signal and sends it to the host computer through the serial communication module after program conversion and calculation, the host computer receives the data and verifies it and saves it in a csv file in the specified path, realizing a gated PMT-LIBS signal acquisition.

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