Field calibration method for variable air volume air conditioning system terminal device

Abstract

The invention discloses an on-site calibration method for a variable air volume air conditioning system terminal device, and relates to the technical field of variable air volume air conditioners, the method comprises the following steps: S1, installing a cross-shaped Pitot tube on a pipeline, and connecting the cross-shaped Pitot tube with a terminal controller; s2, the actually measured pressure difference # imgabs0 # of the tail end controller is read through a communication protocol; meanwhile, the pressure difference # imgabs 1 # at the Pitot tube is measured through a handheld differential pressure gauge; s3, under at least two working conditions, respectively reading a pressure difference # imgabs2 # measured by the handheld differential pressure gauge and an actually measured pressure difference # imgabs3 # of the tail end controller, and finally calculating a pressure difference coefficient k and a pressure difference deviation C through a formula # imgabs4 #; and S4, setting the pressure difference coefficient k and the pressure difference deviation C obtained by calculation into a tail end controller. By means of the handheld differential pressure gauge, relatively accurate calibration of the variable air volume terminal device can be carried out on a project site, the calibration process is simplified, complex laboratory equipment is not needed, and the efficiency of site construction is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of variable air volume air conditioning, and in particular to an on-site calibration method for a terminal device of a variable air volume air conditioning system. Background Art

[0002] The variable air volume system is a full air conditioning system that adjusts the indoor temperature by changing the air volume delivered to the room, and its air supply state remains unchanged. The variable air volume air conditioning system consists of an air handling unit, an air supply system, a terminal device and an automatic control device, among which the terminal device and the automatic control device are the key equipment of the variable air volume system. They can receive instructions from the room temperature regulator and automatically adjust the air supply volume according to the room temperature to meet the indoor load requirements.

[0003] In a variable air volume air conditioning system, the terminal controller measures the real-time air volume, compares it with the required air volume, and then adjusts the valve opening to achieve the purpose of controlling the air volume. Therefore, the accuracy of real-time air volume measurement is very important for the operation of the system. Usually, after determining the brand and model of the variable air volume terminal bellows and the terminal controller, it is necessary to install the terminal controller to the variable air volume terminal bellows before the overall installation to calibrate the actual air volume. The entire calibration process is usually carried out in the factory of the variable air volume terminal bellows manufacturer, and a calibration bench is required.

[0004] After searching, a Chinese patent (publication number: CN104566775B) discloses a variable air volume air conditioning system and control method, which includes the following steps: calculating the required air volume value of the variable air volume terminal according to the preset temperature parameters and the actual temperature parameters; at the same time, detecting the leakage value of the variable air volume air conditioning system; adjusting the speed of the fan in the variable air volume air conditioning system according to the leakage value, the required air volume value and the maximum speed of the fan in the variable air volume air conditioning system, so that the variable air volume terminal supply air volume in the variable air volume air conditioning system is equal to the variable air volume terminal demand air volume in the variable air volume air conditioning system.

[0005] Variable air volume air conditioner - if the terminal controller is replaced, the actual air volume needs to be recalibrated. However, since the variable air volume terminal bellows is large in size and inconvenient to transport back and forth, a relatively accurate on-site calibration method is very necessary. Therefore, the present invention proposes an on-site calibration method for the terminal device of a variable air volume air conditioning system. Summary of the invention

[0006] The object of the present invention is to provide an on-site calibration method for a terminal device of a variable air volume air conditioning system to solve the problems mentioned in the above background technology.

[0007] The present invention can be implemented by the following technical solution: A method for on-site calibration of a terminal device of a variable air volume air conditioning system, the method comprising the following steps: S1. Install a cross-shaped pitot tube on the pipeline to lead out two high and low measuring ports to correspond to the total pressure and static pressure respectively, and connect the two high and low measuring ports to the high and low pressure difference interfaces of the terminal controller respectively; S2. Read the measured pressure difference of the terminal controller through the communication protocol ; At the same time, the pressure difference at the Pitot tube is measured by a handheld differential pressure meter ; S3, through the formula The air volume is measured and ; Where S is the cross-sectional area of ​​the duct, is the air density, is the measured pressure difference of the terminal controller, k is the pressure difference coefficient; Therefore, read the pressure difference measured by the handheld differential pressure meter under at least two working conditions. The measured pressure difference with the terminal controller , and finally through the formula: , calculate the pressure difference coefficient k and pressure difference deviation C; S4. Set the calculated pressure difference coefficient k and pressure difference deviation C to the terminal controller to complete the calibration.

[0008] A further technical improvement of the present invention is that: in step S2, the pressure difference measured by the handheld differential pressure meter is monitored in time series, and after its fluctuation is stabilized, the average value of the pressure difference within a preset time is taken as the pressure difference measured by the handheld differential pressure meter. , the steps include: A1. Measure and continuously record differential pressure data using a handheld differential pressure meter , and determine the recording time interval and the total monitoring time T; A2. Pressure difference data Conduct time series monitoring; From time Start by collecting pressure difference data at N consecutive time points , and recorded as a time series: ; A3. Calculate the fluctuation range and change rate of the time series, including: Compute the mean of a time series: In the formula, is the mean value of the time series, The pressure difference data measured by the handheld pressure difference meter at the i-th time point; The formula for calculating the fluctuation range is: , where R is the fluctuation range of the time series, is the maximum value of the pressure difference data in the time series, is the minimum value of the pressure difference data in the time series; The rate of change of the time series is calculated by calculating the standard deviation of the time series. The formula is: ; Preset the allowed fluctuation range threshold and the preset standard deviation threshold ; When the fluctuation range of the time series R ≤ the fluctuation range threshold , and the time series standard deviation ≤Standard Deviation Threshold When determining the pressure difference data measured by the handheld differential pressure meter Satisfy stability and the pressure difference data at subsequent times Mark as steady-state pressure difference and record the stable time point .

[0009] At stable time Some time later The mean value of the steady-state pressure difference is calculated using the formula: , where is the mean value of the steady-state pressure difference, Z is the number of sampling points corresponding to the time M, The differential pressure data is marked as steady-state differential pressure.

[0010] A5. Repeat steps A1-A4 to calculate the measured pressure difference of the terminal controller marked as steady-state pressure difference ; A6. The measured pressure difference marked as steady-state pressure difference by the terminal controller The pressure difference between the handheld differential pressure meter and the steady-state differential pressure Applied to the calculation in step S3, namely: The air volume calculation formula is: ; The calculation formula for the pressure difference coefficient k and the pressure difference deviation C is: .

[0011] A further technical improvement of the present invention is that under dynamic working conditions, the frequency and fluctuation of the air volume of the variable air volume air conditioner are adjusted, and the frequency and fluctuation of the air volume of the output air volume of the handheld differential pressure meter and the terminal controller are monitored to detect the delay of the air volume change, and the steps include: Z1. By adjusting the air volume input frequency of the variable air volume air conditioner , simulating periodic fluctuations; And by setting multiple input frequencies , observe the response of the variable air volume air conditioning system at different frequencies; Z2. Real-time monitoring of the pressure difference changes of the terminal device, including: The pressure difference time series is collected by a handheld pressure difference meter to record the pressure difference changes at the measuring pitot tube in the pipeline. ; Z3. Record the air volume through the terminal controller ; Z4. Calculate the delay time of the pressure difference change relative to the change of the air intake volume based on the changes of the air intake volume and the pressure difference , ; In the formula, is the phase difference of the change of the air volume outflow relative to the air volume inflow; According to the changes in air intake and air output, calculate the delay time of the change in air output relative to the change in air intake , ; In the formula, is the phase difference of the change of the air volume outflow relative to the air volume inflow; Finally, the system delay time is obtained by the response delay from air intake to pressure difference and the response delay from air intake to air outlet. The formula is: .

[0012] A further technical improvement of the present invention is: for different input frequencies Plot the system delay time under the condition to obtain the frequency response curve; By analyzing the variable air volume air conditioning system at different input frequencies The system delay time under the condition of frequency dependence of the response speed of the variable air volume air conditioning system is determined.

[0013] A further technical improvement of the present invention is that the terminal controller establishes a dynamic correction model based on the system delay time: ; In the formula, is the dynamic pressure difference coefficient, k is the pressure difference coefficient calculated in step S4; α is the delay correction coefficient, which is determined by experimental fitting and reflects the impact of system delay on k; Under dynamic conditions, the air volume calculation formula is corrected to: ; And if it is found that under dynamic conditions, if the pressure difference deviation C deviates from the calibration value, then the formula is: make corrections; In the formula, is the dynamic pressure difference deviation, β is the deviation correction coefficient, which is determined by experimental fitting; By introducing delay correction coefficients α and β, the calibration results can adapt to the changes in dynamic air volume and pressure difference, solving the problem that the traditional calibration method is only applicable to steady-state conditions, thereby reducing the calibration error caused by the delay effect and making the calibration results closer to the actual air volume.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention can perform relatively accurate variable air volume terminal device calibration at the project site through a handheld differential pressure meter, which simplifies the calibration process, does not require complex laboratory equipment, and significantly improves the efficiency of on-site construction. In addition, by using a handheld differential pressure meter and on-site real-time data processing technology, the calibration process does not require high-precision experimental equipment and professional technicians to operate, which reduces the technical difficulty of variable air volume terminal device calibration. And by performing time series analysis on the differential pressure data collected by the handheld differential pressure meter, the technical solution can extract the average value of the differential pressure as the basis for calibration after the fluctuation is stable, avoiding the impact of instantaneous fluctuations on the calibration accuracy. This makes the on-site calibration results closer to the actual operating conditions and ensures the calibration accuracy; At the same time, the solution can deal with problems such as air volume fluctuations and unstable pressure differences that may exist in the on-site environment by introducing dynamic monitoring technology and steady-state pressure difference calculation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0016] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments. Example 1

[0018] See also Figure 1 As shown, the present invention provides an on-site calibration method for a terminal device of a variable air volume air conditioning system, the method comprising the following steps: S1. Install a cross-shaped pitot tube on the pipeline to lead out two high and low measuring ports to correspond to the total pressure and static pressure respectively, and connect the two high and low measuring ports to the high and low pressure difference interfaces of the terminal controller respectively; The high and low pressure difference is measured based on the principle of total pressure - static pressure = dynamic pressure, which is the dynamic pressure. The wind speed flowing through the pipeline is calculated by dynamic pressure, and the air volume can be measured by combining it with the cross-sectional area of ​​the pipeline. S2. Read the measured pressure difference of the terminal controller through the communication protocol ; At the same time, the pressure difference at the Pitot tube is measured by a handheld differential pressure meter ; S3, through the formula The air volume is measured and ; Where S is the cross-sectional area of ​​the duct, is the air density, is the measured pressure difference of the terminal controller, k is the pressure difference coefficient; Therefore, read the pressure difference measured by the handheld differential pressure meter under at least two working conditions. The measured pressure difference with the terminal controller , and finally through the formula: , calculate the pressure difference coefficient k and pressure difference deviation C; S4. Set the calculated pressure difference coefficient k and pressure difference deviation C to the terminal controller to complete the calibration.

[0019] Specific examples: When working, connect the pitot tube on the BOX to the terminal controller and the handheld differential pressure meter through the Y-type interface, and ensure that the + / - pipes are connected correctly; Turn on Bluetooth of the handheld differential pressure meter, install the testo smart APP on your mobile phone, turn on Bluetooth to connect the handheld differential pressure meter through the APP, set the Pitot tube coefficient = 1, set the correction coefficient = 1, and set the area = the area corresponding to 40107 in the terminal controller; In the APP, go to Options - Application Range - My Measurement Field - + Measurement Program - Pressure Difference ( ), enter the upper right corner of the measurement, option-point by point; Connect the terminal controller to the computer via the serial port, open XCVAVConfigTool, modify the connection parameters, connect, and read the device parameters; Click "Full Open" on the APP, and when the air valve opening reaches 100, there will be a reading of "Full Open Pressure Differential". Wait for about 5 seconds (until the air flow is stable), click "Full Open" again and click the "Accept" button on the mobile APP at the same time, and fill the number in the result column on the APP into the "Full Open Measured Pressure Differential" in XCVAVConfigTool; Perform the above operation again in the "half-open" state. Then in XCVAVConfigTool, the full-open / half-open pressure difference of the air valve and the full-open / half-open measured pressure difference will have numbers. At this time, click "Calculate pressure difference parameters" to generate the "pressure difference coefficient K" and "pressure difference offset"; Finally, click "Save Device Parameters" to successfully write the device and the parameters will take effect. Example 2

[0020] A method for on-site calibration of a terminal device of a variable air volume air conditioning system, the method comprising the following steps: S1. Install a cross-shaped pitot tube on the pipeline to lead out two high and low measuring ports to correspond to the total pressure and static pressure respectively, and connect the two high and low measuring ports to the high and low pressure difference interfaces of the terminal controller respectively; The high and low pressure difference is measured based on the principle of total pressure - static pressure = dynamic pressure, which is the dynamic pressure. The wind speed flowing through the pipeline is calculated by dynamic pressure, and the air volume can be measured by combining it with the cross-sectional area of ​​the pipeline. S2. Read the measured pressure difference of the terminal controller through the communication protocol ; At the same time, the pressure difference at the Pitot tube is measured by a handheld differential pressure meter ; The pressure difference measured by the handheld differential pressure meter is monitored in time series, and after its fluctuation is stabilized, the average pressure difference within the preset time is taken as the pressure difference measured by the handheld differential pressure meter. , the steps include: A1. Measure and continuously record differential pressure data using a handheld differential pressure meter , and determine the recording time interval And the total monitoring time T, that is time point; A2. Pressure difference data Conduct time series monitoring; From time Start by collecting pressure difference data at N consecutive time points , and recorded as a time series: ; A3. Calculate the fluctuation range and change rate of the time series, including: Compute the mean of a time series: ; In the formula, is the average value of the time series; The pressure difference data measured by the handheld pressure difference meter at the i-th time point; The formula for calculating the fluctuation range is: ; In the formula, R is the fluctuation range of the time series; is the maximum value of the pressure difference data in the time series, is the minimum value of the pressure difference data in the time series; The rate of change of the time series is calculated by calculating the standard deviation of the time series. The formula is: ; Preset the allowed fluctuation range threshold and the preset standard deviation threshold ; The fluctuation range and standard deviation of the time series are compared with the corresponding fluctuation range thresholds. and standard deviation threshold Make a comparison; When the fluctuation range of the time series R ≤ the fluctuation range threshold , and the time series standard deviation ≤Standard Deviation Threshold When determining the pressure difference data measured by the handheld differential pressure meter Satisfy stability and the pressure difference data at subsequent times Mark as steady-state pressure difference and record the stable time point ; A4. At the stable time point Some time later The mean value of the steady-state pressure difference is calculated using the formula: , where is the mean value of the steady-state pressure difference, Z is the number of sampling points corresponding to the time M, is the pressure difference data marked as steady-state pressure difference; A5. Repeat steps A1-A4 to calculate the measured pressure difference of the terminal controller marked as steady-state pressure difference ; S3, through the formula Measure the air volume; Where S is the cross-sectional area of ​​the duct, is the air density, is the measured pressure difference of the terminal controller, k is the pressure difference coefficient; Therefore, read the pressure difference measured by the handheld differential pressure meter under at least two working conditions. The measured pressure difference with the terminal controller , and finally through the formula: , calculate the pressure difference coefficient k and pressure difference deviation C; S4. Set the calculated pressure difference coefficient k and pressure difference deviation C to the terminal controller to complete the calibration. Example 3

[0021] A method for on-site calibration of a terminal device of a variable air volume air conditioning system, the method comprising the following steps: S1. Install a cross-shaped pitot tube on the pipeline to lead out two high and low measuring ports to correspond to the total pressure and static pressure respectively, and connect the two high and low measuring ports to the high and low pressure difference interfaces of the terminal controller respectively; S2. Read the measured pressure difference of the terminal controller through the communication protocol ; At the same time, the pressure difference at the Pitot tube is measured by a handheld differential pressure meter ; The pressure difference measured by the handheld differential pressure meter is monitored in time series, and after its fluctuation is stabilized, the average pressure difference within the preset time is taken as the pressure difference measured by the handheld differential pressure meter. , the steps include: A1. Measure and continuously record differential pressure data using a handheld differential pressure meter , and determine the recording time interval And the total monitoring time T, that is time point; A2. Pressure difference data Conduct time series monitoring; From time Start by collecting pressure difference data at N consecutive time points , and recorded as a time series: ; A3. Calculate the fluctuation range and change rate of the time series, including: Compute the mean of a time series: ; The formula for calculating the fluctuation range is: ; The rate of change of the time series is calculated by calculating the standard deviation of the time series. The formula is: ; Preset the allowed fluctuation range threshold and the preset standard deviation threshold ; The fluctuation range and standard deviation of the time series are compared with the corresponding fluctuation range thresholds. and standard deviation threshold Make a comparison; When the fluctuation range of the time series R ≤ the fluctuation range threshold , and the time series standard deviation ≤Standard Deviation Threshold When determining the pressure difference data measured by the handheld differential pressure meter Satisfy stability and the pressure difference data at subsequent times Mark as steady-state pressure difference and record the stable time point ; A4. At the stable time point Some time later The mean value of the steady-state pressure difference is calculated using the formula: ; A5. Repeat steps A1-A4 to calculate the measured pressure difference of the terminal controller marked as steady-state pressure difference ; S3, through the formula Measure the air volume; Where S is the cross-sectional area of ​​the duct, is the air density, is the measured pressure difference of the terminal controller, k is the pressure difference coefficient; Therefore, read the pressure difference measured by the handheld differential pressure meter under at least two working conditions. The measured pressure difference with the terminal controller , and finally through the formula: , calculate the pressure difference coefficient k and pressure difference deviation C; Under dynamic conditions, the frequency and fluctuation of the air volume of the variable air volume air conditioner are adjusted, and the frequency and fluctuation of the air volume of the terminal controller are monitored to detect the delay of the air volume change. The steps include: Z1. By adjusting the air volume input frequency of the variable air volume air conditioner , simulating periodic fluctuations, the formula is as follows: ; In the formula, is the air intake volume at time t; is the average air intake volume, which is the reference value of air volume fluctuation; A is the amplitude of the air intake fluctuation, which indicates the maximum range of change of the air intake relative to the average air intake during the fluctuation process; is a sinusoidal function, which represents the periodic change of air volume fluctuation. By multiplying it with A, the fluctuation range of the air volume is obtained [-A, A]; And by setting multiple input frequencies , observe the response of the variable air volume air conditioning system at different frequencies; Z2. Real-time monitoring of the pressure difference changes of the terminal device, including: The pressure difference time series is collected by a handheld pressure difference meter to record the pressure difference changes at the measuring pitot tube in the pipeline. ; Z3. Record the air volume through the terminal controller ; Z4. Calculate the delay time of the pressure difference change relative to the change of the air intake volume based on the changes of the air intake volume and the pressure difference ; ; In the formula, is the phase difference of the change of the air volume outflow relative to the air volume inflow; According to the changes in air intake and air output, calculate the delay time of the change in air output relative to the change in air intake ; ; In the formula, is the phase difference of the change of the air volume outflow relative to the air volume inflow; Finally, the system delay time is obtained by the response delay from air intake to pressure difference and the response delay from air intake to air outlet. The formula is: .

[0022] For different input frequencies Plot the system delay time under the condition to obtain the frequency response curve; By analyzing the variable air volume air conditioning system at different input frequencies The system delay time under the condition of frequency dependence of the response speed of the variable air volume air conditioning system is determined.

[0023] The terminal controller establishes a dynamic correction model based on the system delay time: ; In the formula, is the dynamic pressure difference coefficient, k is the measured pressure difference marked as the steady-state pressure difference and the pressure difference marked as the steady-state pressure difference Calculated α is the delay correction coefficient, which is determined by experimental fitting and reflects the impact of system delay on k; Under dynamic conditions, the air volume calculation formula is corrected to: ; And if it is found that under dynamic conditions, if the pressure difference deviation C deviates from the calibration value, then the formula is: make corrections; In the formula, is the dynamic pressure difference deviation, β is the deviation correction coefficient, which is determined by experimental fitting; By introducing delay correction coefficients α and β, the calibration results can adapt to the changes in dynamic air volume and pressure difference, solving the problem that the traditional calibration method is only applicable to steady-state conditions, thereby reducing the calibration error caused by the delay effect and making the calibration results closer to the actual air volume.

[0024] S4. The calculated dynamic pressure difference coefficient and dynamic differential pressure deviation Simply set it in the terminal controller to complete the dynamic calibration.

[0025] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A field calibration method for a terminal device of a variable air volume air conditioning system, characterized in that: The method comprises the following steps: S1. Install a cross-shaped pitot tube on the pipeline to lead out two high and low measuring ports, and connect the two high and low measuring ports to the high and low pressure difference interfaces of the terminal controller respectively; S2. Read the measured pressure difference of the terminal controller through the communication protocol ; At the same time, the pressure difference at the Pitot tube is measured by a handheld differential pressure meter ; S3. Read the pressure difference measured by the handheld differential pressure meter under at least two working conditions. The measured pressure difference with the terminal controller , and finally through the formula: , calculate the pressure difference coefficient k and pressure difference deviation C; S4. Set the calculated pressure difference coefficient k and pressure difference deviation C to the terminal controller to complete the calibration.

2. The on-site calibration method of a variable air volume air conditioning system terminal device according to claim 1, characterized in that: In step S3, the measured pressure difference through the terminal controller The air volume is calculated using the formula: ,and ; Where S is the cross-sectional area of ​​the duct, is the air density, is the measured pressure difference of the terminal controller, and k is the pressure difference coefficient.

3. The on-site calibration method of a terminal device of a variable air volume air conditioning system according to claim 1, characterized in that: In step S2, the pressure difference measured by the handheld differential pressure meter is monitored in time series, and after its fluctuation is stabilized, the average pressure difference within the preset time is taken as the pressure difference measured by the handheld differential pressure meter. .

4. The on-site calibration method of a terminal device of a variable air volume air conditioning system according to claim 3, characterized in that: The method for obtaining the mean value of the differential pressure of the handheld differential pressure meter comprises the following steps: A1. Measure and continuously record differential pressure data using a handheld differential pressure meter , and determine the recording time interval and the total monitoring time T; A2. Pressure difference data Conduct time series monitoring; From time Start by collecting pressure difference data at N consecutive time points , and recorded as a time series: ; A3. Calculate the fluctuation range and change rate of the time series, including: Compute the mean of a time series: , where is the mean value of the time series, The pressure difference data measured by the handheld pressure difference meter at the i-th time point; The formula for calculating the fluctuation range is: , where R is the fluctuation range of the time series, is the maximum value of the pressure difference data in the time series, is the minimum value of the pressure difference data in the time series; The rate of change of the time series is calculated by calculating the standard deviation of the time series. The formula is: ; Preset the allowed fluctuation range threshold and the preset standard deviation threshold ; When the fluctuation range of the time series R ≤ the fluctuation range threshold , and the time series standard deviation ≤Standard Deviation Threshold When determining the pressure difference data measured by the handheld differential pressure meter Satisfy stability and the pressure difference data at subsequent times Mark as steady-state pressure difference and record the stable time point ; A4. At the stable time point Some time later The mean value of the steady-state pressure difference is calculated using the formula: , where is the mean value of the steady-state pressure difference, Z is the number of sampling points corresponding to the time M, The differential pressure data is marked as steady-state differential pressure.

5. The on-site calibration method of a variable air volume air conditioning system terminal device according to claim 4, characterized in that: Repeat steps A1-A4 to calculate the measured pressure difference of the terminal controller marked as steady-state pressure difference ; The measured differential pressure of the terminal controller is marked as the steady-state differential pressure The pressure difference between the handheld differential pressure meter and the steady-state differential pressure Applied to the calculation in step S3, namely: The air volume calculation formula is: ; The calculation formula for the pressure difference coefficient k and the pressure difference deviation C is: .

6. The on-site calibration method of a terminal device of a variable air volume air conditioning system according to claim 5, characterized in that: Under dynamic conditions, the frequency and fluctuation of the air volume of the variable air volume air conditioner are adjusted, and the frequency and fluctuation of the air volume of the terminal controller are monitored to detect the delay of the air volume change. The steps include: Z1. By adjusting the air volume input frequency of the variable air volume air conditioner , simulating periodic fluctuations; And by setting multiple input frequencies , observe the response of the variable air volume air conditioning system at different frequencies; Z2. Real-time monitoring of the pressure difference changes of the terminal device, including: The pressure difference time series is collected by a handheld pressure difference meter to record the pressure difference changes at the measuring pitot tube in the pipeline. ; Z3. Record the air volume through the terminal controller ; Z4. Calculate the delay time of the pressure difference change relative to the change of the air intake volume based on the changes of the air intake volume and the pressure difference , ; In the formula, is the phase difference between the change of the air volume outflow and the air volume inflow; According to the changes in air intake and air output, calculate the delay time of the change in air output relative to the change in air intake , ; In the formula, is the phase difference between the change of the air volume outflow and the air volume inflow; Finally, the system delay time is obtained by the response delay from air intake to pressure difference and the response delay from air intake to air outlet. The formula is: .

7. The on-site calibration method of a variable air volume air conditioning system terminal device according to claim 6, characterized in that: The terminal controller establishes a dynamic correction model based on the system delay time: ; In the formula, is the dynamic pressure difference coefficient, k is the pressure difference coefficient calculated in step S4, and α is the delay correction coefficient.

8. The on-site calibration method of a variable air volume air conditioning system terminal device according to claim 7, characterized in that: Under dynamic conditions, the air volume calculation formula is corrected to: And under dynamic conditions, if the pressure difference deviation C deviates from the calibration value, the formula is: Make corrections; where is the dynamic pressure difference deviation, and β is the deviation correction coefficient.

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