Design and implementation of electronic measurement workstation based on virtual instrument technology

The rapid development of modern industry and national defense industry has brought electronic measurement technology into the stage of widespread use and comprehensive measurement. On-site monitoring and test equipment for large-scale equipment and systems is a new market that is in the ascendant. The core of comprehensive test equipment is composed of a multi-category, high-performance cluster of electronic measuring instruments and computers, and it emphasizes the applicable scope of user interface signals and the ability of equipment to adapt to harsh working environments. With the widespread use of large-scale comprehensive tests in equipment and systems, the demand for large-scale field test equipment will grow day by day. The emergence of electronic measurement workstations just fills this gap and can effectively solve the problem of emergency repair of equipment. Electronic measurement workstations use virtual instrument technology to combine computers, instrument hardware, computer software, etc. In addition to inheriting the existing functions of traditional instruments, they also add many advanced functions that traditional instruments cannot achieve. They are highly flexible and break through the limitations in data processing, transmission and storage. The USB interface has become a standard configuration of PCs, and supports hot-swap functions and high data transmission rates.
Based on NI's USB series data acquisition cards and LabVIEW virtual instrument development platform, a portable comprehensive measurement system is built to measure the parameters of the equipment in the frequency domain and time domain, and complete the status detection and troubleshooting of the equipment.

1 Virtual Instrument
A virtual instrument is an instrument that uses a computer as the hardware core platform, and hardware with corresponding test functions as the signal input/output port. The instrument development software is used to virtualize the instrument panel and function buttons on the computer, and the instrument is operated by the mouse and keyboard. The hardware uses a data acquisition card, and the user can virtualize an instrument with any function. The LabV-IEW software designed by National Instruments is a graphical programming environment that realizes the concept of virtual instruments. Compared with traditional instruments, virtual instruments realize the intelligence, modularization, and diversification of measuring instruments, have a fully automated test process, and can be easily developed secondary, as well as at a lower cost.

2 System Design
2.1 Introduction to Electronic Measurement Workstation
The electronic measurement workstation is a new type of measuring equipment that combines 15 types of electronic measuring instruments with a computer. It is an important innovation in today's electronic instrument industry. It has the characteristics of small size, easy to carry, sturdy, high temperature resistance, vibration resistance, impact resistance, absolute sealing and waterproofing, corrosion resistance, moisture resistance, and dust resistance. In particular, its powerful instrument cluster comprehensive working ability is particularly suitable for
providing necessary repair platforms for equipment in harsh environments and emergency tests. The various instruments in the electronic measurement workstation can work synchronously to form a collaborative instrument cluster. It conforms to the current trend of diversification and integration of electronic measurement, replaces traditional discrete desktop instruments in the form of workstations, and provides a new type of electronic measurement equipment for the industrial, scientific and educational sectors. It has complete functions, is easy to use, has good versatility and high cost performance. Therefore, electronic measurement workstation products have the potential to become an important growth point in the field of electronic instruments today. The basic characteristics of the electronic measurement workstation are as follows: it integrates a multi-channel, multi-functional electronic measurement instrument group with a computer into an electronic measurement device with large-scale comprehensive measurement capabilities; it has a standard target hardware adaptation interface; it has a standard target software adaptation interface.
2.2 System composition
The electronic measurement workstation consists of two parts: hardware and software.
The hardware part is based on the USB bus data acquisition card, equipped with corresponding auxiliary circuit modules to complete signal acquisition and conversion. The module circuits include bidirectional digital signal adapter circuit, digital storage oscilloscope circuit, high-speed sampling memory circuit, data model waveform memory circuit, arbitrary waveform voltage source signal generator circuit, voltage signal waveform memory circuit, arbitrary waveform current source signal generator circuit, current signal waveform memory circuit, multimeter circuit, DC regulated power supply circuit, and communication control module circuit.
The software part uses the LabVIEW graphical programming software of National Instruments, the instrument driver completes the software program for controlling and communicating with a specific instrument, and the computer stores and analyzes the data.
2.3 System Function
The electronic measurement workstation uses the system synchronization control module as the circuit core to control the synchronization of various instruments and functional modules. In the measurement, the target to be measured is connected to the corresponding instrument in the electronic measurement workstation through the measurement interface adapter to complete the transmission and measurement of the required signal. The measurement data is processed by the computer and the measurement data and images are displayed. The instrument and functional module circuit it controls are shown in Figure 1.

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The basic functional components of the system are as follows: dual-channel digital storage oscilloscope; dual-channel FFT spectrum analyzer; 18-channel logic analyzer; digital multimeter, LCR multi-purpose bridge; frequency meter (microwave); 18-channel data model signal generator, arbitrary waveform voltage source, current source signal generator, clock signal generator; adjustable DC regulated power supply, industrial frequency AC power supply.

3 System Implementation
The system synchronization control module is the control core of the equipment, which controls the work of various related components. It can coordinate the synchronous work and synchronous trigger of various instruments; it can communicate with the host computer through the communication control module, receive commands and transmit data. Various instruments are composed of system synchronization controllers and corresponding modules. Take the logic analyzer as an example for introduction.
3.1 System synchronization controller
The system synchronization controller has a powerful event trigger, which can identify specific signal events according to the parameters set by the host computer, and can perform logical operations, trigger counting and delay control on the events. The trigger signal of its event can be used to control the working state of the equipment. At the same time, it also has 12 groups of 18-bit width code signal event identifiers, 1 group of 16-bit width bus signal event identifiers, 2 groups of 6-level queue triggers, 12 groups of signal width identifiers, and 2 groups of 51-bit counters/timers. Its timing capability can reach 260 days and the timing accuracy is 10 ns. These high-performance components provide rich signal trigger resources and are suitable for capturing high-speed instantaneous signal flows. The system synchronization controller also has a system synchronization bus and supports dual-machine online working mode. In the online working mode, the trigger resources of the two systems can be synthesized, and can be triggered and worked synchronously. The system synchronization bus can also be used to accurately calibrate the frequency of the main clock.
The structure of the system synchronization controller is shown in Figure 2.

3.2 Logic Analyzer The
digital signal adapter, high-speed sampling memory and control circuit in the system synchronization control module constitute an 18-channel logic analyzer with a sampling rate of 200 MS/s and a storage depth of 1 megapoint. It has rich signal triggering and synchronization capabilities, and its signal measurement bandwidth is 80 MHz. The digital signal adapter has bidirectional signal processing capabilities. It can send the digital signal of the system under test to the logic analyzer in the system synchronization control module for measurement, and can also send the output signal of the data model generator to the system under test to drive the signal node of the system under test.
When working, the digital signal adapter switches the transmission direction of the digital signal of each channel in real time under the control of the system synchronization controller. The structure of the digital signal adapter is shown in Figure 3.
When measuring, the logic analyzer first locks the external measured signal through the signal latch, and the locked signal DinBUS is sent to the direction controller. The control register adjusts the timing of signal locking and the direction of signal transmission according to the signal of the system synchronization control module. The measured signal driven by the direction controller is sent to the system synchronization control module. The system synchronization control module stores the measured signal in high-speed sampling memory in real time and generates a pre-set trigger process. [page]

The high-speed sampling memory stores the digital signals sent by the oscilloscope and logic analyzer in real time. After sampling, the data in the high-speed sampling memory is sent to the host computer through the system synchronization controller and the communication control module. It has a data width of 34 bits and an address space of 1 MB. It works under the drive of the sampling clock signal MSBUS-CLK and the control signal MSBUS-C output by the system synchronization controller. The structure of the high-speed sampling memory is shown in Figure 4.

3.3 Software Structure
The logic analyzer based on virtual instrument technology mainly consists of two parts: data capture and data display. The data input part transforms the input of each channel into the corresponding data stream; the trigger generation part searches for specific data words in the data stream according to the data capture method, and then decides whether to generate a trigger signal to control the data storage to start or stop storing data. The data display part displays the valid data in the storage in a variety of ways, which is convenient for analyzing the captured data. The main program flow chart is shown in Figure 5.
The design of the logic analyzer adopts a modular concept, including the main program module, DAQ signal acquisition module, multi-channel simulation signal generation module, merged data stream module, analog-to-digital conversion module, multi-channel waveform connection module, channel setting module, sequence trigger module, trigger setting module, intercepted waveform module, etc. The main program directly calls multiple subVI programs. The operation interface is shown in Figure 6.

4 Conclusion
This paper introduces an electronic measurement workstation system based on the concept of virtual instrument. The system realizes the integration of multiple instruments, is simple to operate, easy to carry, and provides an important platform for rapid maintenance of equipment.