How to realize the requirements of constant temperature and humidity control cabinet?

Constant temperature and humidity control cabinet is one of the more extensive control systems of central air conditioning system, which is widely used in hospitals, laboratories, clean workshops and other fields. What are the components of the constant temperature and humidity control system and how to realize it? Let's discuss it with you today.
1. Controller of constant temperature and humidity control cabinet: at present, the core of the control system is the controller. The brands of controllers include Siemens series, Mitsubishi controller, and domestic ones include Xichuang, Yonghong, Hollysys, etc. S7-200 is widely used in Siemens controller, with high reliability. It has been widely used in industrial and civil control fields for many years and has been tested for a long time. Extremely rich instruction set. It can easily realize the compilation of various application software. It has rich built-in integration functions and powerful communication capabilities
S7-200 controller
2. Temperature and humidity sensor of control cabinet:
Equipment location: air conditioning return duct
Temperature range: 0 ~ 50 ℃
Humidity range: 0-100%
Output signal: 0-10vdc
Power supply: 24vac/dc
3. Water valve actuator of constant temperature and humidity control cabinet:
Location of equipment: return pipe of cold water coil of air cabinet
Control signal: 0 ~ 10VDC 4-20mA
Power supply: 24VAC
It can be operated manually
Water valve actuator
4. Air differential pressure switch of control cabinet
Equipment position: front and rear of fan, primary / medium / high efficiency filter screen
Pressure difference range: 20 ~ 300pa / 50 ~ 500pa
Output signal: passive contact
5. Air supply volume control
According to the air volume requirements of the system, the frequency of the frequency converter can be set in the manual operator and the central monitoring to meet the air volume control requirements of the end equipment
6. Temperature and humidity control of air conditioning unit
According to the temperature and humidity of the return air, control the cold / hot water valve, electric heating, and control the temperature and humidity of the room;
When the return air temperature is higher than the set temperature, the proportional integral opens the cold water valve; When the return air temperature is lower than or close to the set temperature, the proportional integral closes the cold water valve, and judges whether the temperature is high or low, and whether the electric heater is put into operation to raise the temperature. When the return air humidity is higher than the set humidity, the proportional integral opens the cold water valve for cooling and dehumidification; When the return air humidity is lower than or close to the set humidity, the proportional integral is closed
7. Air conditioning unit maintenance
The unit is equipped with primary / intermediate efficiency filter blockage alarm, fan failure alarm, electric heating high temperature protection alarm and other functions. When the filter screen is blocked due to long-term use, the controller will send the primary / intermediate efficiency filter blockage alarm at the same time, prompting the maintenance personnel to replace or clean it; If the fan is overcurrent or locked, the controller will send out the fan fault alarm, and the fan will stop immediately at the same time; The outlet temperature of the electric heater is too high, and the high temperature protection alarm of the unit will be given. At the same time, the electric heater will be turned off immediately
The above is a simple analysis of the composition and control principle of the constant temperature and humidity control system. Of course, the central air conditioning control system is complex, and its control options are also diverse. Especially in hospital operating rooms and laboratories, the requirements for control accuracy are higher. Constant temperature and humidity control system is also more complex.