Abstract: This paper introduces a development scheme for a solenoid valve testing device based on CPCI bus technology. The portability requirement of the testing device is achieved through the insertion design of the sampling control board and sampling module. Practical applications show that this tester can meet the testing requirements of various types of ordinary solenoid valves and self-locking valves. Keywords: Compact PCI, Portable tester, Solenoid valve, Test 1. Introduction Due to the need for factory completion of thermal vacuum testing of a certain type of solenoid valve, the valve response characteristics need to be tested during the test. Traditional testing equipment cannot meet transportation requirements due to its size, therefore, a portable solenoid valve testing device is needed. CompactPCI, abbreviated as CPCI, is a bus interface standard proposed by the international PICMG association in 1994. It combines the dense and robust packaging of VME with the excellent cooling effect of large equipment and the low cost and easy adoption of the latest processing capabilities of PC chips, which not only ensures a high reliability of 99.999%, but also greatly reduces the hardware and software development costs. Its overall structure is compact, the installation is firm, it is adaptable to various transportation conditions, and the reliability is high. Each functional board adopts the modular structure of CPCI bus, which is very safe and convenient to plug and unplug, and is particularly suitable for the requirements of various test objects and various test conditions of this system. 2. Design requirements (1) It is required to be able to test 3 self-locking valves or solenoid valves at the same time, and have automatic and manual interpretation functions. The single sampling frequency is not less than 10KHz, and the test results can be output to the printer. (2) The control voltage of the solenoid valve is variable from 0 to 50V, and the maximum current is not less than 12A. (3) The number of actions, pulse width, and interval are all adjustable. The number of actions is variable from 0 to 1000; the interval is variable from 0 to 10000ms; the pulse width is variable from 0 to 3000ms. (4) The discharge resistor is adjustable in three ranges: 10Ω, 50Ω, and 100Ω. (5) Applicable to various types of solenoid valve testing requirements. (6) Equipment size requirements: 30cm×30cm×50cm, weight not exceeding 25kg, and meeting the requirements for Class III highway transportation . 3. Testing Principle and System Composition The testing principle of the solenoid valve is shown in Figure 1. The test resistor is connected in series in the solenoid valve circuit. The valve coil current value is calculated by measuring the voltage divider signal across the test resistor. The voltage signal across the sampling resistor is converted into a voltage signal between 0-5V by an isolation amplifier and input into the A/D board for conversion into a digital quantity. Considering the problem of excessive voltage division of the sampling resistor under high current, the sampling resistors are all high-power, high-precision resistors with a current of less than 1 ohm. The purpose of using a 16-bit precision A/D board is to ensure sufficient system testing accuracy under low-value test resistor conditions. [align=center]Figure 1 Schematic diagram of solenoid valve testing[/align] The system composition is shown in Figure 2, mainly consisting of an ACME GCP-382 computer, an external DC power supply, an A/D board (16-bit), a control drive board, a sampling board, an isolation amplifier, and various cables. The GCP-382 computer includes a single-board computer and a monitor. It is equipped with an IDE interface, allowing system installation via an external optical drive. Normal data input and output are conducted through USB and network interfaces. The control board and sampling board are designed with backup boards to accommodate different types of valves. The test interface, sampling circuit, and test software of the test equipment should all adopt a configurable design approach, combining different test states according to different test objects. Six data acquisition channels are set up, with a single-channel sampling frequency of not less than 10KHz. A maximum of three self-locking valves can be tested simultaneously, and six ordinary solenoid valves can be tested at the same time. However, the self-locking valves tested simultaneously should have the same state (both positive terminal control or all negative terminal control). [align=center]Figure 2 Working Principle Diagram of the Detector[/align] Switching between the sampling resistor and the discharge resistor involves replacing the sampling resistor board, therefore it must be switched before testing and cannot be hot-switched during testing. The sampling single channel is directly related to the object under test; therefore, different combinations of the objects under test result in different sampling circuit boards. Since the combination of the objects under test cannot be determined, the design provides four of the most commonly used sampling circuit boards. The control power supply is external, and the power parameters can be customized by the user. The control accuracy during valve action is ≤±2ms, the system time test accuracy is ≤±0.1ms, and the system current test accuracy is ≤0.03A. Adapter Cables: Different test cables are provided for different valve connectors, and the device end of the cable uses a universal interface. 4. Hardware Design Sampling Module: Different sampling resistors and discharge resistors are provided according to different test objects. This detector designs four different combinations of sampling boards. The size and structure of the sampling board are the same as the 3U board of the CPCI bus, embedded in the host chassis for easy insertion and removal. The main ports include: ports for connection to the A/D board, ports for connection to the control board, and valve ports. The sampling board panel has A/D and valve interfaces, with each loop designed for a current of over 8A; the sampling board's bleed resistor is replaceable; the test resistor is 0.4 ohms for self-locking valves and 0.8 ohms for ordinary valves; the solenoid valve cable connector is of the easy-to-plug type. The control drive board uses an FPGA as the controller, communicating with the host computer via a bus for autonomous control, driving solid-state relays to control the valve under test. This control drive board can determine the positive and negative control methods according to the host computer's instructions. The drive board's size and structure are the same as the 3U board of the CPCI bus, embedded in the host chassis for easy insertion and removal. It connects to the host via a bus and to the outside via ports. The main connection ports include: a DC power port and a port for connection to the sampling board. The system receives commands via a bus, performs autonomous timing and control; the power circuit has 6 channels with 12 solid-state relays (controlling 6 positive and 6 negative terminals respectively), controlling a current of over 10A. Each channel has an easily removable 8A fuse, and each channel has an LED display on the panel showing its operating status; the cable connecting the control board and the sampling board can be installed inside the chassis, the connector is lockable, the cable is flexible, and its length allows a board to be pulled out of the chassis and exposed at the socket position. Test cables: Different test cables are provided for different valve connectors, and the equipment ends of the cables use universal interfaces. 5. Software Design The solenoid valve testing software is written in general-purpose C++, and the background database uses an ACCESS database. After setting the test information, the solenoid valve under test is automatically tested through the driver of the designed hardware. The automatic interpretation function can directly output the test valve response characteristics. The database allows for querying and outputting the test records of the solenoid valve. [align=center]Figure 3. Test parameters of the solenoid valve obtained directly through automatic interpretation[/align] After the test system controls and tests the valve under test, it directly writes the test results and other data into the database. The information stored includes not only the characteristic values ​​of the solenoid valve current curve, but also: working pulse width, working interval, number of actions, test voltage, test unit (test location), test status, product status, load condition, test date, and product information of the valve under test. The characteristic curve of the solenoid valve coil current is shown in Figure 3. Its characteristic values ​​are opening time, opening current, steady-state current, closing time, closing current, opening ratio, and closing ratio. These characteristic values ​​are obtained by software interpretation of the data. For newly acquired test data or test data from a second opening, the "automatic interpretation" function is used to automatically interpret the solenoid valve test curve. Due to the wide variety of valve types and test states, automatic interpretation may result in misjudgments. The software employs an automatic interpretation algorithm based on artificial intelligence technology. It analyzes and learns from test results under various valve conditions using a large amount of accumulated historical data, using the analysis results as an auxiliary interpretation basis for test objects under the same conditions, thus greatly improving the accuracy of interpretation. Furthermore, the accuracy of automatic interpretation continues to improve as test data accumulates. For misjudgments in special cases, the software uses a manual interpretation function as a supplement, allowing manual adjustment of the curve feature point positions to ensure the correctness of the interpretation results. 6. Conclusion The innovation of this paper is the successful design of a portable solenoid valve tester using CPCI bus technology. After its successful development, compared with traditional test systems with equivalent functions, this system is 50% smaller in size and 70% lighter, and is simple to operate, highly reliable, and easy to carry. This application achieves the universality requirements of solenoid valve test instruments, meeting the testing needs of various types of ordinary solenoid valves and self-locking valves. Good expandability can be achieved by adding sampling modules, interface cables, and test software. References: [1] Liu Cun. Modern Detection Technology [M]. Beijing: Machinery Industry Press, 2005. [2] Yang Gang, Long Haiyan, Yang Xi. New Trends in the Development of Computer Bus. Microcomputer Information. 2003-01. [2] Lei Tianjue, Yang Erzhuang, et al. New Hydraulic Engineering Handbook [M]. Beijing: Beijing Institute of Technology Press, 1998.