P0917XQ dcs module – Foxboro

Description

Many people confuse aging with high-temperature testing. Actually, this is completely different. The high-temperature testing of the product is mainly to check whether the product can work normally in the designed high-temperature working range. For example, if the working temperature of the PLC is 55 degrees, as long as the machine is turned on within the range of 55 degrees for operation testing, it is sufficient after the temperature in the module reaches stability (usually about half an hour).

However, aging is a completely different concept. Each component of a product has a certain lifespan, for example, electronic components have a lifespan of 10 years. During this lifespan, the failure rate in the first three months is very high, and then it will become lower and lower. After three months, when it reaches stability, the failure rate will decrease to a relatively low level, until around 10 years, when the device reaches its lifespan, the failure rate will begin to rise again. Aging in the production and manufacturing process refers to the process of operating at high temperatures to shorten the time when the product has a high failure rate in the early stages, so that the product can cross this stage and enter a low failure rate stage before leaving the factory.

The temperature and time of aging are related to different types of products. For electronic products, if set at a temperature of 55-60 degrees Celsius, the high failure rate in the early stage can be reduced from three months to about three days. This is why many electronic products have an aging time of 72 hours. Therefore, aging is an important process in the production process of PLC products, and cannot be simply seen as a testing process. Knowing the above principles, one will also understand that the aging process of a product is very important, and the testing after aging is even more important. Because, for modules that are prone to failure, the vast majority of potential faults will be exposed during the aging process, therefore, strict testing must be carried out on the aged products. The testing methods and methods are similar to the module testing methods before aging, but all must be fully tested. Some testers believe that the product has already been tested once, so they often relax the testing of aged products. In fact, this is a big mistake and particularly wrong.

The above four steps are an introduction to the hardware testing of PLC. As software is also an important component of PLC, it is also necessary to test the internal software of PLC. Usually, due to product confidentiality reasons, even for outsourced modules, the company’s key software must be installed internally, and related testing functions must also be completed within the company. Software functional testing can be divided into low-level embedded software testing and programming software testing.

The underlying embedded software refers to the system software of the PLC, which is the embedded solidification software (FIRMWARE) within the CPU module of the product. In the CPU module of the industrial control system, there is an IC chip that contains the solidification system software of the CPU. Usually referred to as SOC (System On Chip), this SOC is the core of the controller. There are two main ways to implement SOC: ASIC and FPGA. At present, Dewison’s main embedded software is solidified using FPGA technology, so here we will only briefly introduce the testing process of FPGA chips. When conducting chip testing during the manufacturing process, the first step is to entrust the raw material inspection of FPGA chips to the supplier. The company conducts monthly spot checks to ensure that the quality of the chips themselves is not affected; At the same time, the software to be embedded must have passed FPGA sample debugging and the functionality has been qualified. The chip first writes the software through the chip writer, and then the tester inserts the chip into the testing circuit. A logic analyzer is used to analyze and test the predetermined pin waveform of the chip. In order to ensure 100% testing of the chip, this step only tests the waveforms of a few key points. After the logic test is completed, the chip is subjected to electrical performance testing, which mainly tests the high and low limits of the chip’s working voltage and automatic recovery performance. After the electrical performance test is completed, aging testing of the chip will begin.

After aging, perform another logical analysis test and select at least 5% of the chips for comprehensive performance testing, mainly to observe the software functions of the chips for design modification reference. The testing of product programming software is usually not conducted during the manufacturing process, and I will describe it in the testing of product application processes. The above manufacturing process testing mainly refers to performance testing. In addition, specialized reliability testing is also required for PLC products. The reliability testing of products includes environmental testing, mechanical performance testing, and electrical performance testing. Mechanical performance testing mainly tests the mechanical integrity of product packaging, including the firmness of welding points, the precision of molds, and the firmness of wiring terminals. Environmental testing mainly tests the durability (or lifespan, usually calculated as mean time between failures) of products stored and used under harsh conditions. Electrical performance testing is used to verify whether a product can withstand various electrical environments in the upcoming environment. According to relevant national regulations, reliability testing (including EMC, vibration and impact, and dust testing) can be conducted at authoritative professional testing institutions after the production of the first batch of samples for each product, and then once a year at a government professional testing center for inspection.

The company only conducts pressure resistance and high and low temperature aging tests on products internally, and does not need to conduct reliability tests on each batch of each product. Environmental testing includes high temperature, low temperature, salt mist, dust, flammable and explosive gases, humidity, altitude testing, etc; Mechanical performance testing includes vibration, impact, accelerated stress, etc; Electrical performance testing includes EMC electromagnetic compatibility tests (including radiation characteristics, static electricity, group pulse, etc.), contact tests (mainly for switch input and output modules), and voltage withstand tests. The products submitted for inspection are randomly sampled, usually two sets.