PID Temperature Controller AI-708P
In 1995, our company purchased a cadmium telluride single crystal furnace from Ukraine. The temperature controller used in the single crystal furnace equipment is a meter composed of many discrete components. The circuit is complicated and has many faults, which often affects the operation of the equipment. In 1998, we decided to renovate this single crystal furnace equipment and replace the Ukrainian non-standard instrument with the AI-708P standard controller.
1. Selection of instruments
Through the investigation, we decided to replace the Ukrainian instrument with the Yudian AI-708P instrument or the British Continental 818 instrument. At that time, in the domestic single-crystal furnace equipment, the European 818 instrument was used. In other words, it is no problem to replace the Ukrainian instrument with the Euro 818 meter. Because the price of continental instruments is expensive, I want to use domestic instruments instead of foreign instruments.
I analyzed the performance of the AI-708P meter and compared the performance and price of the AI-708P meter and the Continental 818 meter. Firstly, it is proposed whether the A1-708P instrument can meet the process requirements of the cadmium telluride single crystal furnace. The mercury cadmium telluride crystal is the material required for the infrared device. The growth process of the crystal is about 30 days, and the length of the crystal growth time is determined by the process.
The setting time of the AI-708P meter is 9999 minutes, about 7 days; the time of the Euro 818 meter is set to 999.9 hours (minutes), about 42 days. Although the time setting of the AI--708P is not enough for 30 days, the AI-708P has 30 programs. If you fully utilize the 30-segment program function, you can meet the 30-day time requirement. In addition, the highest display temperature and lowest temperature resolution of the AI-708P meter can meet the process requirements.
Although the Continental 818 has many features, it is expensive. The price of each Euro 818 meter is 7,000 yuan, while the price of AI-708P is 1200 yuan per unit. Obviously, the performance price ratio of AI-708P is high. In 1998, Yuguang (formerly known as Yudian) was first exposed, but its popularity was not high. People lacked understanding of the field application of AI-708P instruments. At the beginning of 1998, I went to the Xiamen Yuguang Research Institute to participate in an academic exchange meeting. I saw that the Yuguang Institute had a spirit of hard work. After returning to Beijing, I will work on replacing Ukrainian instruments with AI-708P meters. The equipment transformation work was relatively smooth, and the task was completed shortly. After years of equipment operation test, it proves that the AI-708P instrument has reliable performance and can fully meet the process requirements of the cadmium telluride single crystal furnace.
2. Control principle of cadmium telluride single crystal furnace
The temperature programming of the AI-708P instrument is now listed below, and the temperature control circuit diagram of the single crystal furnace is attached for reference.
Table 1: Temperature schedule
C01=20.0 starts to increase from room temperature 20.0 °C t01=60 after 60 minutes
C02=250.0 liters to 250.0°Ct01=120 after 120 minutes
C03=250.0 insulation at 250°Ct03=120 after 120 minutes
C04=450.0 liters to 450.0°Ct04=90 after 90 minutes
C05=450.0 insulation at 450.0°Ct05=300 after 300 minutes
C06=820.0 rises to 820.0°Ct06=8640 after 8640 minutes
C07=820.0 insulation at 820.0°Ct07=8640 after 8640 minutes
C08=820.0 insulation at 820.0°Ct08=8640 after 8640 minutes
C09=820.0 insulation at 820.0 °Ct09=8640 after 8640 minutes
C10=820.0 insulation at 820.0°Ct10=4320 after 4320 minutes
C11=820.0 insulation at 820.0°Ct01=360 after 360 minutes
C12=350.0 drops to 350.0°Ct12=600 after 600 minutes
C13=20.0 drops to 20.0°Ct13=-121 stops
See figure 1: Temperature degree map
See figure 2: Single crystal furnace temperature control circuit diagram
Circuit description: AC power supply is used after step-down of transformer, output voltage is 25V, output current 28A, MJYD-JL-75 is thyristor intelligent module, including thyristor and phase shift control circuit, output maximum voltage is 450V, maximum current is 75A, L1 is Overcurrent protection fuse, RC is an overvoltage protection RC component. RW is an electric furnace wire. The output of A1-708P is 0-10MA current. After 1K resistor, the output becomes 0-10V DC voltage, which satisfies the input voltage requirement of the thyristor module.
The S thermocouple is connected to the rear end of the AI-708P meter via a compensation wire.
3. Feasibility analysis of single crystal furnace temperature control system selection
In the single crystal furnace temperature control system, in addition to the A1-708P instrument is the core components, there are thermocouples, compensation wires, heating furnaces, power regulators and other important components. A thorough understanding of the performance of these components is also important to the proper selection of these components. The current temperature instrument, economical and practical type of each hundred yuan, and the basic configuration price of each advanced instrument is several thousand yuan, if you add a few functional modules, the price can be tens of thousands. For a certain process, it is sufficient to use a temperature meter that meets the technical requirements and can operate stably and reliably. It is not necessary to use a more advanced temperature meter. It is scientific to select the type of temperature meter with a performance-price ratio indicator. Saving resources and making the best use of it is also the principle of selecting the type of temperature instrument.
Since the adoption of Yudian AI-708P as the main core control system, the control operation of the cadmium telluride single crystal furnace has been in good condition, and there is still no fault. It can completely replace the imported Continental 818 meter. Regardless of the actual operation situation or the cost performance, the choice of AI-708P can fully meet the requirements.