Water meter automatic calibration device based on Delta Automation

1 Introduction

The static volumetric water meter calibration device based on Delta PLC technology can calibrate magnetoelectric water meters (with remote transmission) and ordinary water meters. The automatic calibration device uses a friendly monitoring interface to realistically simulate the layout and dynamic working conditions of on-site equipment. The device has parameter setting and modification functions. The device obtains on-site data in real time and processes and displays it in a timely manner. At the same time, the various collected data are saved in a specific historical database, and the calibration data form is automatically filled in and the calibration results are printed.

2 Design conditions

2.1 Legal design basis

This project is designed and manufactured in accordance with the national metrological calibration regulations "JJG164-2000" "Calibration Regulations for Liquid Flow Standard Devices", "JJG634-94" "Calibration Regulations for Standard Meter Method Flow Standard Devices", "JJG162-94", "Calibration Regulations for Water Meters and Their Test Devices".

2.2 Calibration device structure

The working volume structure is shown in Figure 1. The working volume meters are available in four specifications: 10 L, 20 L, 100 L and 300 L, which can be used to calibrate flow meters of corresponding standard volumes.

Figure 1 Workload meter structure diagram

2.3 Conversion Relationships

(1) The relationship between the volume, scale value, and volume per millimeter of the measuring neck of a standard working volume is shown in Table 1.

(2) Conversion formula for the standard volume of the working volume in actual work:

Vactual = Vstandard + (Lactual - Lstandard) * α

Where:
Vactual: The actual amount of water injected into the working volume through the water meter during calibration.
Vstandard: The standard value of the working volume.
Lactual: The actual value of the measuring neck.
Lstandard: The indicated value of the measuring neck under the standard volume of the working volume.
α: The volume value of the measuring neck per millimeter.

(3) Indication error formula [3]

Among them:
δ: basic error.
V indicated: the amount of water recorded by the water meter during calibration.
V actual: the actual amount of water injected into the working meter through the water meter during calibration.

3. Device principle design

3.1 Device principle

The system block diagram is shown in Figure 2. Install the water meter horizontally on the test bench, use the nominal flow rate allowed by the water meter to pass water, remove the air in the water meter and the outlet pipe, and make the water meter pointer rotate steadily for a period of time. Then adjust the water flow to the specified flow value, put the water in the working meter to zero or a certain scale line, start the commutator solenoid valve and the corresponding measurement control solenoid valve, synchronize with the water meter pointer, switch the water flow to inject it into the working meter, and record the starting value of the water meter. When the water meter pointer reaches the predetermined scale, switch the water flow again, wait for the water level of the working meter to be still, and then read the water. The running water volume of the water meter and the actual water volume of the working meter are collected in the computer. At this time, the computer processes the collected relevant data to obtain the basic error of the corresponding point, and calibrates other calibration points in turn. When all the calibration points are calibrated, the computer will process the final calibration results and print them out.

Figure 2 System working principle block diagram [page]

3.2

The circuit diagram of the water level measurement circuit of the differential pressure transmitter is shown in Figure 3. The differential pressure transmitter adopts the EJA110 type produced by Yokogawa Instrument Co., Ltd. It is a high-precision (±0.075%, continuous operation for five years without adjustment, and the influence of temperature and static pressure is negligible) two-wire differential pressure transmitter. Its function is to convert the water level signal of the working volume into a 4-20mADC current signal. This current signal is connected to the DFP-1100M type distributor. The distributor provides an isolated power supply for the two-wire EJA110 differential pressure transmitter installed on site, and at the same time converts the 4-20mADC signal sent by the two-wire transmitter into an isolated 1-5VDC signal. This 1-5VDC voltage signal is given to the programmable controller as a standard signal for automatic control.

Figure 3 Differential pressure transmitter and distributor wiring diagram

4 PLC monitoring system design

The programmable controller (PLC) host uses Delta DVP-ES/EX/SS series programmable controller DVP14SS11R2. Power supply voltage: 24VDC; input points: 8 points; output points: 6 points; output form: relay. The analog input module uses Delta DVP-04AD. The analog input range is ±10V, the digital conversion range is ±2000, and the resolution is 12bit. [2] The input, output port and storage unit allocation are shown in Table 2. The CPU module circuit design is shown in Figure 4, the expansion module circuit is shown in Figure 5, and the program flowchart is shown in Figure 6.

Figure 4 Wiring diagram of programmable controller DVP14SS11R2

Figure 5 PLC DVP-04AD wiring

Figure 6 Flowchart [page]

5 Configuration of automatic calibration device

5.1 KingView software

The configuration software used is KingView software 6.51 of Beijing Yakong Technology Development Co., Ltd. It is a commercial industrial measurement and control configuration software running on Windows NT/2000/XP Chinese operating system. It has a complete graphical interface generation function and can vividly depict the industrial scene. It provides full-featured controls and control functions as well as a variety of I/O drivers.

5.2 KingView communication parameters and device configuration

(1) Communication parameters: Baud rate: 9600; data bits: 7; parity check: even check; stop bit: 1; communication timeout: 3000 milliseconds; communication mode: RS232.
(2) Device configuration: Device manufacturer: Juteng anco; device name: delta; device logical name: PLC; device address: 1; communication mode: serial port (COM1).

5.3 PLC configuration link variables

The corresponding relationship between KingView variables and programmable controller registers is shown in Table 3.

Table 3 Correspondence between KingView variables and PLC registers

5.4 Interface Design

(1) The start-up and standard value and actual value interfaces of the calibration device are shown in Figure 7. The standard volume of the measuring instrument, standard volume scale, actual volume scale, millimeter equivalent, actual standard volume, frequency of the meter under test, instantaneous flow rate of the meter under test, control liquid level, frequency accumulation, current accumulation, and working time are analog value input connections; the frequency coefficient, current coefficient, and liquid level setting are analog value input and output connections.

Figure 7 Calibration device startup and standard value and actual value interface

The buttons "Actual standard volume calculation", "Large tank start", "Small tank start", "Stop", and "Total reset" are command language connections when they pop up. Due to space limitations, the specific command language is abbreviated.

(2) The calibration point selection interface is shown in Figure 8. A radio button control is used to implement the selection of the calibration point [1]. Control name: calibration point selection; variable name: calibration times; title data: nominal flow, boundary flow, minimum flow.

Figure 8 Calibration point selection interface

Due to limited space, the command language connection of the "Frequency Data Filling Table" and "Current Data Filling Table" buttons is omitted when they are popped up.

(3) The data storage and printing interface is shown in Figure 9. Data storage and printing are implemented using a list combo box control and some buttons [1]. List combo box control, control name: list box; variable name: number of calibration records.

Figure 9 Data storage and printing selection interface

Due to limited space, the buttons "Data Storage", "Data Reading", "Add", "Clear", "Print Settings", and "Print Preview" are linked to the command language when they are popped up. The specific command language is omitted.

6 Conclusion

The static volumetric water meter automatic calibration device adopts advanced programmable controller and configuration software technology to eliminate errors caused by manual operation, greatly improving the efficiency and accuracy of water meter calibration. It has achieved good results through its use in the Xinglongtai oil production in Liaohe Oilfield.

References
[1] Beijing Yakong Technology Development Co., Ltd. Configuration King Version 6.51 User Manual [M], 2005.
[2] Zhongda Electric Co., Ltd. DVP Programmable Controller User Manual [M], 2006.
[3] Zhejiang Provincial Metrology and Verification Institute. Verification Procedure for Water Meters and Their Test Devices JJG162-94, 1985: 14.
[4] Zhang Taifeng. Water Meters and Their Verification. Beijing: China Metrology Press, 1990: 155.