Method 4 requires the customer to have a steam source or a hot water source, and is also subject to certain restrictions on application promotion. A new method for constant temperature regulation of air conditioners. In response to the above situation, some experts have developed high-precision constant temperature and humidity air conditioners that overcome the above-mentioned unfavorable factors. The temperature accuracy is as high as ±0.2 °C and the humidity accuracy is as high as ±3%, and passed the acceptance at the end of 2004. Temperature and humidity are highly accurate and very constant over a year of operation. Studio net volume: 4.2m (width) × 8.0m (deep) × 2.5m (height), indoor illumination: 500lx; required temperature 22 ° C ± 0.3 ° C, humidity 60% ± 3%. The parameters of the air conditioning unit are selected: air volume: 8000m3/h, cooling capacity: 26kW, humidification capacity 13kg/h, unit heating capacity: 15kW, air supply duct heating capacity: 6kW, which is a conventional PF26 engine room dedicated air conditioner plus 6kW air duct electric heater. The method is implemented by using a conventionally configured PF26 constant temperature and humidity unit plus a 6 kW duct electric heater. The duct electric heater is installed in the air supply duct. In the control, the detection and control of the supply air temperature and humidity are added on the basis of the conventional constant temperature and humidity control system of the author. The supply air temperature and humidity are controlled and regulated by the supply air duct heater. The air duct heater is steplessly adjusted by a PID algorithm using a solid state relay. Because the heating amount of the air duct heater is small, the cost of the solid state relay used is not too high. The measuring instrument only needs to increase the supply air temperature and humidity transmitter, so the cost of the entire control scheme does not increase much. In the air treatment system, only the duct heater is added, and the installation of the duct electric heater is relatively simple in engineering, and the cost is relatively low, and is not affected by the presence or absence of steam or hot water source of the customer. Reflect the economics of this program. The specific control process is divided into two parts: 1 The conventional constant temperature and humidity unit performs cooling, heating, humidification, dehumidification, etc. according to the temperature and humidity of the controlled room (ie return air) and the set temperature and humidity and the required temperature and humidity accuracy. In the air treatment process, in order to solve the contradiction between temperature and humidity during the whole control process, the temperature-priority control principle is adopted, that is, after the temperature is first reached the set temperature, the start of the dehumidification process is considered. During the dehumidification process, if the temperature deviates from the set temperature, the electric heating is performed to perform group compensation. Through such control, the room temperature and humidity are kept as close as possible to the set value, which is a coarse adjustment. 2 The electric heater in the air supply duct is mainly used to ensure that the difference between the supply air temperature and the set temperature is relatively constant, thereby ensuring the temperature and humidity caused by the reheat compensation of the duct heater during the low temperature dehumidification process. The resulting fluctuations. The control process is specifically controlled by the difference between the supply air temperature and the set temperature and the current working mode of the constant temperature and humidity unit, and the main function is to finely adjust the temperature and humidity precision. Assuming that the absolute value Δt of the difference between the supply air temperature and the set temperature is to be ensured, when the constant temperature and humidity unit is in the process of cooling or high temperature dehumidification and the difference between the set temperature and the supply air temperature is greater than Δt, the air is supplied. The electric heating in the air duct starts to load until the difference between the set temperature and the supply air temperature ≤ Δt, and the supply of the wind power is constant at this time, and the heating amount is output and is no longer loaded. When the constant temperature and humidity unit is in heating or low temperature dehumidification and the difference between the supply air temperature and the set temperature is ≤ Δt, the electric heating in the air supply duct starts to load until the difference between the supply air temperature and the set temperature ≥ △ t, the supply of wind power is constant at the current heating output and is no longer loaded. The ultimate goal of this control is to ensure that the air supply temperature is lower than the set temperature by taking into account factors such as air absorption through the duct when the unit is cooled or dehumidified at high temperature. In the heating or low-temperature dehumidification of the unit, the air supply temperature is higher than the set temperature by taking into account the air cooling through the air duct and other factors. Δt. As long as the Δt is constant, the temperature in the controlled room is relatively constant due to the temperature and The relationship of humidity ensures the accuracy of humidity indirectly while ensuring temperature accuracy. In the setting of the control parameters, the PID adjustment parameters of the duct electric heater, the absolute value of the difference between the supply air temperature and the set temperature Δt are all open parameters, which can be considered according to the actual situation of the specific project (mainly considering The heat dissipation and dehumidification equipment has a large difference due to each specific project. The test verification is part of the data obtained by the customer's on-site monitoring computer from the developed high-precision constant temperature and humidity unit under the PROFIBUS DDP communication protocol. Conclusion From the above test results, it can be seen that this control idea and control method can achieve the expected results, the temperature accuracy is ±0.2 ° C, the humidity accuracy is up to ± 3%, fully meet the requirements of the use of high temperature and humidity requirements. The successful development of high-precision constant temperature and humidity air conditioners has solved some problems in this type of machine over the past few years, alleviating the contradiction between the start and stop limits of compressors and the high-precision requirements of temperature and humidity, while increasing the cooling capacity or electricity. The design of the heating amount is more reasonable and advanced. At present, the units that achieve high precision requirements in China are often complicated to manufacture and costly. The method adopted by the author can meet the requirements of high precision and has good application and promotion value. 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