Overview of water meter test bench:
In order to meet the requirements of liquid flow meter verification, calibration, factory inspection, and the growing trend of new flow meter production, improve the meter inspection efficiency of users in the field of water meter production and measurement, and reduce labor costs, our company has designed and manufactured an active flow meter with water as the medium. Piston liquid flow standard device;
The relevant technical parameters are as follows:
Device flow range
(2-6300) L/h
Test bench accuracy
≤0.2% (k = 2)
Ambient temperature
15 - 30℃
Relative humidity
(45% - 75%)
Working pressure
(86 ~ 106)kpa
Air source pressure
(3.5 ~ 6) bar
Collection method
camera direct reading, infrared, M-BUS, RS485
Equipment power
water pump 2.2KW, heating 6KW
Number of inspection meters
ultrasonic water meters (DN15: 10 pieces, DN20: 10 pieces, DN25: 8 pieces)
Equipment size
length, width, and height (5800mm*1500mm*2000mm)
This standard device has many advantages such as stability and reliability, good repeatability, a high degree of automation, and easy operation. The unique design avoids the shortcomings of the start-stop effect or commutator effect of traditional liquid flow standard devices, greatly improving measurement uncertainty. The device also has the characteristics of self-contained, compact structure, high efficiency, and energy saving. There is no need to build a pool or special structural requirements for the building. It is very suitable for production testing and product development testing of small flow metering instruments. This calibration device has been exported to overseas markets and has been exported to the European Union, Australia, and other countries many times. It has cooperated with multiple scientific research projects in "industry, academia and research" and has been deeply involved in the market for many years and has rich experience.
Structural composition and details of water meter test bench:
This device consists of a water source system, a meter clamping pipeline, a flow regulating device, a standard system, a commutator device, an image acquisition system, and a software control system. Its basic working principle is to compare the intercepts of the piston cylinder within a certain time interval. The volume flow rate of the discharged fluid obtained by multiplying the area and the piston displacement is compared with the volume flow rate of the flow meter being tested.
1) Water source system
The water source system includes a water pump, a water tank, an automatic pressure device, and a vacuum device. The water pump is of the Southern Pump Industry brand, with a maximum flow rate of 8m³/h and a head of 100m. It is controlled by a Danfoss inverter, and the software can set different frequencies. The pipeline is equipped with a balloon-type pressure stabilizing tank, which stabilizes the pressure of large flow disturbances. For Q2 and Q1 flow, the piston water supply is used to ensure stable flow.
The water tank is made of 304 stainless steel with a volume of 500L. The bottom is equipped with a liquid level, temperature sensor, heating device and outer insulation device. It can monitor the liquid level and temperature in real-time. The water temperature control accuracy can reach ±1℃; the maximum set pressure of the pressure device is 2.5MPa. , the pressure can be set by the software, and the pressure and pressure relief are controlled by the PLC; the vacuum device can extract all the bubbles in the wet water meter to facilitate direct-read image data recognition by the camera.
2) Clamp meter pipeline
The meter inspection pipeline consists of the clamping device of the meter being inspected, pipelines, switch valves, etc. The clamping device of the meter under inspection is also called a meter clamp. It can adjust the distance according to the length of the meter and can clamp the meters under inspection of various specifications. The meter clamping device of this equipment adopts an external cylinder-type clamping mechanism, which effectively prevents internal air leakage caused by damage to the sealing ring due to long use. The meter clamping device of this device uses three optical axes as positioning points, and the optical axes are installed To the stainless steel fixed plate used for wire cutting production, the coaxiality is good.
The front and rear straight pipe sections are made of POM material with a very small coefficient of thermal expansion and contraction, and the slider is processed in one step using a CNC machining center.
The device adopts a single-row reversible meter clamping mechanism driven by a servo motor. The flipping of the meter clamping mechanism is beneficial to the vacuuming effect of the wet water meter, eliminating air bubbles and water stains on the dial, and at the same time increasing the acquisition success rate of image recognition.
3) Flow regulating device
The device is equipped with three flow point pipelines and uses two electromagnetic flowmeters as flow indication devices. Below 250L/h, DN2.5 caliber electromagnetic display is used, and above 250L/h, DN25 electromagnetic display is used. It is equipped with three flow point pipelines, which are used to adjust Q3 respectively. \Q2\Q1 flow point.
During automatic detection of the device, the software automatically adjusts and detects the required flow points based on the flow range, pump frequency, valve opening, and other parameters set by the control parameters. Each flow point is equipped with a pneumatic ball valve to control which electromagnetic flowmeter to use. , when the software detects that the current flow rate does not match the set flow rate, the software automatically controls the water pump frequency or the opening of the pneumatic control valve to adjust the required flow rate.
When the detected flow rate is within the range of 500L-8000L, the device can be equipped with a Samson pneumatic regulating valve with a flow adjustment accuracy of <2%. When the detected flow rate is below 500L, a piston is used to automatically push out a stable flow rate.
4) Standard device
The standard device adopts a combination of piston and electronic scale. When the flow is ≤500L, the piston is used as the standard to provide flow. The high-speed counter collects the displacement pulse of the grating ruler to measure the standard volume. When the flow is >500L, the water pump provides the flow.
The electronic scales and electromagnetic flowmeters of the device adopt internationally renowned brands. The device uses METTLER TOLEDO's 120KG/6000E electronic scale as the standard instrument. Electronic scales of different brands and accuracy can be selected according to the size of the water meter tested. The electronic scale is independently installed on the outside of the main body of the equipment, which reduces the error caused by the vibration of the equipment to the electronic scale and facilitates the calibration of the electronic scale.
The basic working principle of the piston system is to compare the volume flow rate of the fluid discharged by the piston within a certain time interval with the volume flow rate of the flow meter being tested. The volume of fluid discharged by the piston is obtained by multiplying the cross-sectional area of the piston cylinder and the piston displacement; the piston is Driven by a 22L Panasonic servo motor, the top of the piston is equipped with a temperature sensor with Class A accuracy and a measuring range of 0-100°C and a Hangzhou Miko pressure sensor with an accuracy of 0.5%. It is used to measure water temperature and water pressure and compensate for the piston bore error. Equipped with a German ELGO grating ruler to measure the displacement of the piston and improve the accuracy of displacement measurement.
The active piston liquid flow standard device is shown in the figure above and mainly consists of a frame, piston rod, piston cylinder, motor, ball screw, supporting optical axis, sensor, protective shell, etc.
The piston rod is in close contact with the piston cylinder through the Y-shaped sealing ring. The three together form a sealed cavity. The movement of the piston rod is realized by the servo motor, coupling, ball screw, supporting optical axis, etc. The piston rod and the ball screw are The rod is connected through a screw nut, and the movement direction is controlled by a servo motor and a ball screw. A water suction pneumatic valve and a drainage pneumatic valve are installed at the outlet of the piston cylinder. The water suction pneumatic valve is connected to the water tank, and the drainage pneumatic valve is connected to the meter inspection pipeline. There are Install high-precision temperature and pressure sensors and install limit protection switches.
The core parts of the active piston liquid flow standard device are the piston rod and piston cylinder. Under the condition of ensuring sealing, the product of the outer diameter volume of the piston rod and the horizontal movement distance of the piston rod is the standard cumulative flow rate given by the device. Therefore, the processing accuracy of the piston rod, the sealing between the piston rod and the piston cylinder, and the accurate detection of the piston stroke within the calibration time period are the core of the device design.
Active piston devices can be divided into two categories: piston type and plunger type according to their structural forms. The piston type is in close contact with the piston cylinder through a sealing device, and the inner diameter of the piston cylinder is used as the measurement standard. Therefore, the inner wall of the piston cylinder needs to be finished, and the roughness of the inner wall and the roundness of the cylinder also have strict requirements. However, due to the influence of the length and diameter of the cylinder, it is difficult to process the inner wall of the piston cylinder, and the machining accuracy is difficult to guarantee. The plunger type uses the outer diameter of the plunger as the measurement standard, so the machining accuracy of the plunger is required to be higher. Nowadays, the machine The level of processing can ensure very good roundness and surface tolerance for the outer diameter of the plunger. The plunger type has a simple structure and a relatively reliable seal. The sealing ring is installed at the entrance of the piston cylinder for easy replacement. The form of the piston liquid flow standard device designed by the device is a plunger piston standard device.
Why choose an automatic water meter test bench with a piston device?
1. Stable flow and high calibration accuracy
2. There is no start-stop effect, and a stable flow rate can be achieved in 1S.
3. The clamping table has high concentricity and no air bubbles.
4. Automatic meter inspection, one-click operation
5. Piston automatic calibration system
6. Safety protection measures
7. No temperature is generated, the water temperature is constant
5) Commutator device
The device uses a flip-plate commutator as the flow-switching device. The commutator uses a rotating cylinder, which has the advantages of small vibration and fast switching speed. The uncertainty of the commutator is better than 0.05%. The commutator has been installed tested and calibrated at the factory. Photoelectric sensor, the user can switch at any time through the switch. The software of this device has the uncertainty detection function of the commutator transit time method. The user can detect the uncertainty error of the commutator by himself through the software during use.
The commutator adopts a rotating cylinder T ≤50ms, U4≤0.05%
6) Image acquisition system
What are the advantages of image acquisition systems?
Advantage 1: The image collection range is wide and no special alignment is required. As long as the dial pointer is within the range of the collected images, it can be recognized.
Advantage 2: It can be verified twice. After the test is completed, the software will automatically save the initial value and final value photos. If you have any objection to the test results of a certain table, you can query and save the pictures for review.
Advantage 3: High collection accuracy, collection error is within 0.001L
Advantage 4: Easy to install. The camera uses a POE-powered Ethernet industrial camera. It only needs one network cable to connect to the switch and the switch network cable to the computer network port.
7) Software control system
7-1) Software control system - hardware part
The control system mainly consists of industrial computers, PLC control systems, servo motors, grating rulers, various temperature and pressure sensors, pneumatic ball valves, platform software, etc. Industrial computers have strong anti-interference properties, which can make the calibration process more stable and reliable; PLC and servo motors are from internationally renowned brands with high precision and reliability.
Sensor:
The main sensors include a temperature sensor and a pressure sensor, which are located at the outlet of the piston cylinder. They are used to measure the temperature and pressure of the liquid respectively, and then transmit the information to the PLC and software system in a timely manner.
Sensors are important components for collecting analog quantities such as temperature, pressure, humidity, etc. Their accuracy and performance will directly affect the accuracy of the device's measurement results. Therefore, it is necessary to comprehensively consider various factors and select the most cost-effective sensor product. In this device, the temperature measurement range of the temperature sensor is (0~100)ºC, and the accuracy level is not less than 0.1℃; the pressure measurement range of the pressure sensor is (0~1.6)MPa, and the accuracy level is not less than 0.2% level.
Grating ruler:
The standard cumulative flow rate of the active piston liquid flow device is the product of the internal cross-sectional area of the piston and the piston displacement within the time period. Therefore, accurate measurement of the piston displacement is one of the key factors to reduce the uncertainty of the device. In order to improve the accuracy of displacement measurement, this device uses a grating ruler to measure the displacement of the piston. The output signal of the grating ruler is an AB orthogonal signal, which is improved by 4 times based on the original accuracy.
Servo motor:
The driving element of the servo system is a servo motor. The servo motor converts the voltage signal into torque and rotational speed to drive the control object. Changing the voltage signal can change the rotational speed and steering direction of the servo motor. Servo motors have the characteristics of large starting torque, wide operating range, no rotation, and high positioning accuracy. They are widely used in various automation control systems. Compared with stepper motors, servo motors have the following advantages:
You will get efficient and thoughtful service from tnma.
1. Higher control accuracy;
2. It has good low-frequency characteristics and will not vibrate at low speeds;
3. It has different torque-frequency characteristics. It can output rated torque within its rated speed and constant power output above the rated speed;
4. It has strong speed overload and torque overload capabilities, and the maximum torque is 2~3 times the rated torque;
5. The servo drive system is a closed-loop control. The driver can directly sample the motor encoder feedback signal, and internally constitutes a position loop and a speed loop, making the control performance more reliable; the rotational inertia of the rotary body part of the shaft, kg·cm2
6. The AC servo system has good acceleration performance and can be used in control situations that require quick start and stop.
Reasonable selection of servo motors is the key to designing a motion control system. During design, all requirements must be fully considered in order to give full play to the performance of the servo motors.
Speed matching. The selection of a servo motor should first ensure that the stroke speed of the device does not exceed the rated speed of the motor. In order to make full use of the power of the servo motor, the stroke speed should be as close as possible to the rated speed of the motor.
Torque matching. The rated torque of the servo motor must be greater than the maximum torque of the load, but there is no need to leave too much margin because the maximum torque of the servo motor is generally 2 to 3 times its rated torque. The torque calculation formula of the device is:
F——axial load, N;
L——screw lead, m;
η——mechanical efficiency;
i——transmission ratio
The moment of inertia of the load needs to match the inertia of the servo motor. The large moment of inertia leads to large mechanical constants of the system, reducing servo accuracy and response speed. Therefore, during mechanical design, the moment of inertia should be minimized without affecting the stiffness of the system.
Jd = J L + J S
JL——The moment of inertia of the moving parts converted to the motor shaft, kg·cm2;
JS——Moment of inertia of the rotary body parts converted to the motor shaft, kg·cm2
PLC control system
The PLC control system of this device adopts Siemens S7-200smart system, uses ladder diagram programming language, and mounts analog input and output modules to collect and control temperature and pressure signals.
7-2) Software control system - software part
The software of this device is written in VISUAL STUDIO C# and uses the Microsoft ACCESS database. The detection process can be written into the database, and users can modify the control process according to different permissions. The software has an automatic meter reading function, which can be added to the software according to the user agreement to realize the collection of water meters and automatic correction of errors. After the detection, the error data is automatically saved to the database, and users can query the error data at any time.
Parameter settings:
Used to modify control parameters. According to national calibration regulations, instruments need to detect multiple flow points during the flow detection process. The parameter setting screen can add instrument parameters of different specifications and models according to user needs. After the addition, the data is saved to the database for the next time. When using, directly select the added specifications and models to call the instrument parameters added at that time.
Automatic detection program:
After setting the control parameters, click Auto Detection to enter the automatic detection program. The program runs according to the calibration point set by the control parameters. Before automatically detecting the flow point, the program will perform vacuuming, air bubble removal, and pressure suppression procedures. If these are not required, To operate, just turn off the corresponding switch in the instrument parameters.
Alarm display:
On the right side of the detection screen is the status display area. The running status information displays the current running distance of the piston and displays parameters such as temperature and pressure so that the user can understand the piston's operation in real-time. The software is set with multiple alarm prompts, such as a piston limit switch alarm, high-temperature alarm, high-pressure alarm, low-air pressure alarm, etc. You can view the alarm information and alarm level on the touch screen human-computer interaction interface, and solve the fault according to the instructions. When communication is normal, the indicator light in the communication status bar displays green. When communication fails, the indicator light of the corresponding device displays red.
Data query management:
Data query currently includes traffic original record and traffic certificate record data query. Users can query the detected data according to different query conditions. Users can print the queried data in report form according to their needs.
Report management:
The software is equipped with an open user report system, and users can edit calibration certificates and calibration records according to their own needs. Just write specific characters in the position of the variable that needs to be inserted, and the software will automatically insert the variable value.
This automatic testing platform adopts fully automatic control, fully automatic detection, and intelligent data processing and statistics. It has high meter inspection efficiency. It is driven by a servo motor to reduce the disturbance to the liquid flow, effectively solve the interference of water mist and bubbles, and has high calibration accuracy. It has the following characteristics :
1. Compared with traditional manual calibration devices, the operation is simple, and the computer calculates errors throughout the process to avoid human factors;
2. Improve the efficiency of meter inspection. The original manual meter inspection device takes 30 to 40 minutes to inspect a batch of water meters, and the upgraded automatic water meter inspection device only takes 5 to 8 minutes to inspect a batch of water meters. The meter clamping pipeline adopts an external cylinder-type clamping mechanism, which effectively prevents internal air leakage caused by damage to the sealing ring due to long use. The spacing can be adjusted according to the length of the meter, and inspection meters of various specifications can be clamped;
3. Save energy, water, electricity, and labor; small size, space-saving, fully automated, shared network, saving auxiliary materials. The flow adjustment device can automatically adjust and detect the required flow points according to the flow range, pump frequency, valve opening, and other parameters set by the control parameters. Each flow point is equipped with a pneumatic ball valve to control which electromagnetic flowmeter to use. When the software detects that the current flow rate does not match the set flow rate, the software automatically controls the water pump frequency or the opening of the pneumatic control valve to adjust the required flow rate;
4. The data management function is strong. The software can automatically complete the entire inspection process and draw calibration conclusions. It can save all water meter calibration data and has perfect functions such as calibration record query, correction, statistics, and printing. The camera direct reading acquisition method uses a POE camera and only needs one network cable to connect to the switch, and the switch network cable to the computer network port. The image collection range is wide and does not require special alignment. As long as the dial pointer is within the range of the collected images, it can be recognized. It can be verified twice. After the test is completed, the software will automatically save the initial value and final value photos. If you have any objection to the test results of a certain table, you can query and save the pictures for review. The collection accuracy is high, the collection error is 0.001L, and it also supports M-BUS, RS485, and other communication interfaces;
5. The structure is novel, the appearance is high-end, the industrial design and aesthetics are integrated, and the hardware and software complement each other, which can make the calibration process more stable and reliable;
S.H.Meters has rich technical experience, digs deep into product upgrades and process innovation, and pays no attention to every detail. While ensuring excellent product quality, we also ensure your production efficiency. Advanced equipment, rich experience, and excellent reputation will protect your production and are your best choice.
Device configuration selection table
Mainstream calibration
electronic scale
Flow range (m³/h)
0.002-6.3
Water pump
Nanfang pump 2.2KW/100H/8m³/h
Maximum working pressure (bar)
16
Number of water meters to be inspected
DN15(165mm)*10 pieces
DN20(195mm)*10 pieces
DN25(225mm)*8 pieces
Flip watch platform
No
Piston specifications
volume 22L/resolution 0.036ml/pressure PN16/Panasonic servo drive
Electronic scale
Toledo 120KG/6000E
Weighing container
120L
Electromagnetic flowmeter
YokogawaAXG/DN2.5+DN25
Commutator
DN25
Temperature sensor
PT100, accuracy level A, installed at the inlet and outlet
Pressure sensor
Hangzhou Miko pressure transmitter, accuracy 0.5%, installed at the inlet and outlet
Test method
start-stop method + commutator method
Standard signal interface
MBUS/485/infrared
Equipment power
10KW
Water and electricity
users provide AC400V three-phase five-wire power supply/purified water/6bar air pressure
Quote
Contact us
In this guide, you’ll find everything you need to know to get started with water meter testing programs, including:
All mechanical utility meters (water, gas, electric) will decrease in accuracy over time. Water meters from 5/8” to 2” in size leave the factory with a measurement accuracy of 100% +/- 1.5% registration as per AWWA standards. Positive displacement meters which are typically used in residential and light duty commercial settings do not over register by design and cannot be calibrated. Water meters in general tend to register less usage (slow down) as they get older. Over time mechanical water meter accuracy can be affected by three main components:
The practice of statistical sample testing of water meter populations has been around for quite some time and is also used in the gas and electric meter industry as well. It involves the testing of meters that are a randomly selected from the overall meter population. The batch of meters selected is generally a statistically relevant sample size such that the number of water meters chosen will properly represent the overall population of meters. Sample testing is important because the tests results of the group of meters selected will help a utility to map out a meter replacement strategy for the remainder of the metering system.
Sample Batch Test In Progress
The American Water Works Association (AWWA) is the current standard for cold potable water meter use in North America to date. Measurement Canada (MC) enacted legislation in 1985 that governs the units of measure used in Canada for the custody transfer of products. MC has the right to regulate any measuring device such as weigh scales, gas pumps and even utility meters. Currently MC regulates natural gas and electric meters in Canada and have chosen to leave water meters as status quo. This means that water utilities throughout North America continue to do what they have been doing for the last 120 years which is to self-regulate water meter sizing, selection, testing, and replacement cycles based on the AWWA standards.
The benefits of statistical meter sampling for water purveyors are:
Typically, water billing is the second largest component of a municipality’s cash register next to tax revenue. This makes it super important for water utilities to keep the water meters as close to a hundred percent accurate for as long as possible. As water meter accuracy declines over time so does the annual water budget revenue. In most cases a cost justification can be made to replace the water meters on new meter revenue increase alone.
Starting a dry meter on the low flow test may lead to false representation of actual low flow accuracy. It is recommended that after removal from service that water meters be capped at each end with a small amount of water left remaining in the meter. Starting at the highest flow rate helps the meter to acclimate to measurement again since the meter may have been sitting for a couple of weeks between removal of service and arrival at test facility.
Test rates vary by meter size however all meters are tested at a minimum of three flow rates high, intermediate, and low. Water demand in a home is not constant, so testing at different flow rates gives us a better representation of the meter’s overall or weighted average accuracy.
All water meters decline in accuracy over time due to water quality factors such as turbidity and hardness as well as years in service, including amount of consumption metered. Positive displacement water meters are typically designed to sustain reasonable accuracy over a 20-year period. Historical test data shows us that we can expect somewhere between 3-5% accuracy decline within this period mostly occurring in years 15-20. Since a considerable amount of residential consumption occurs at low and intermediate flow rates much of the accuracy decline throughout the meter’s installation period will occur at these rates. Meters beyond 20 years old can expect test results to show accuracy decline anywhere between 5-10%.
Know your water meter system! A water meter database is only as good as the quality of data entered into it. Some practices to consider when creating an overall testing plan:
Sample Batch of Aged Meters For Testing
Most statisticians will agree that 100 water meters would be the minimum sample size for any meaningful data conclusions. Many say that the maximum would be 10% of your meter population (up to 1,000 meters) would be the maximum representative sample. Going above 1,000 meters tested won’t add much to the accuracy profile you are creating and would add significantly to the meter testing budget.
Bottom line is that there is no perfect plan, start somewhere as it’s better than not starting at all. If uncertain about the best approach, contact an industry professional for a consultation. It will help you to determine the best overall fit for your requirements.
Evans Supply Limited helped the City of Port Colborne’s business case to replace 6,000 water meters twenty years after their original installation. The city removed 170 water meters from their system and testing determined that 40% of the randomly selected batch were not registering accurately. The meter test results played an important role in their business case to replace their aging water meter population.
Start building your meter test database today. Whether you’re replacing a meter for a technology upgrade or any other work order, don’t scrap the meter immediately. Set it aside for batch testing. Once you’ve accumulated a box or two send it to your local test facility. Over the duration of your meter population life cycle, you will have accumulated test data that fairly represents the state of your system. This data will enable the utility staff to confidently justify their meter replacement line item in the budget. Get in contact with us today to arrange for some sample testing!
Overview of water meter test bench:
In order to meet the requirements of liquid flow meter verification, calibration, factory inspection, and the growing trend of new flow meter production, improve the meter inspection efficiency of users in the field of water meter production and measurement, and reduce labor costs, our company has designed and manufactured an active flow meter with water as the medium. Piston liquid flow standard device;
The relevant technical parameters are as follows:
Device flow range
(2-6300) L/h
Test bench accuracy
≤0.2% (k = 2)
Ambient temperature
15 - 30℃
Relative humidity
(45% - 75%)
Working pressure
(86 ~ 106)kpa
Air source pressure
(3.5 ~ 6) bar
Collection method
camera direct reading, infrared, M-BUS, RS485
Equipment power
water pump 2.2KW, heating 6KW
Number of inspection meters
ultrasonic water meters (DN15: 10 pieces, DN20: 10 pieces, DN25: 8 pieces)
Equipment size
length, width, and height (5800mm*1500mm*2000mm)
This standard device has many advantages such as stability and reliability, good repeatability, a high degree of automation, and easy operation. The unique design avoids the shortcomings of the start-stop effect or commutator effect of traditional liquid flow standard devices, greatly improving measurement uncertainty. The device also has the characteristics of self-contained, compact structure, high efficiency, and energy saving. There is no need to build a pool or special structural requirements for the building. It is very suitable for production testing and product development testing of small flow metering instruments. This calibration device has been exported to overseas markets and has been exported to the European Union, Australia, and other countries many times. It has cooperated with multiple scientific research projects in "industry, academia and research" and has been deeply involved in the market for many years and has rich experience.
Structural composition and details of water meter test bench:
This device consists of a water source system, a meter clamping pipeline, a flow regulating device, a standard system, a commutator device, an image acquisition system, and a software control system. Its basic working principle is to compare the intercepts of the piston cylinder within a certain time interval. The volume flow rate of the discharged fluid obtained by multiplying the area and the piston displacement is compared with the volume flow rate of the flow meter being tested.
1) Water source system
The water source system includes a water pump, a water tank, an automatic pressure device, and a vacuum device. The water pump is of the Southern Pump Industry brand, with a maximum flow rate of 8m³/h and a head of 100m. It is controlled by a Danfoss inverter, and the software can set different frequencies. The pipeline is equipped with a balloon-type pressure stabilizing tank, which stabilizes the pressure of large flow disturbances. For Q2 and Q1 flow, the piston water supply is used to ensure stable flow.
The water tank is made of 304 stainless steel with a volume of 500L. The bottom is equipped with a liquid level, temperature sensor, heating device and outer insulation device. It can monitor the liquid level and temperature in real-time. The water temperature control accuracy can reach ±1℃; the maximum set pressure of the pressure device is 2.5MPa. , the pressure can be set by the software, and the pressure and pressure relief are controlled by the PLC; the vacuum device can extract all the bubbles in the wet water meter to facilitate direct-read image data recognition by the camera.
2) Clamp meter pipeline
The meter inspection pipeline consists of the clamping device of the meter being inspected, pipelines, switch valves, etc. The clamping device of the meter under inspection is also called a meter clamp. It can adjust the distance according to the length of the meter and can clamp the meters under inspection of various specifications. The meter clamping device of this equipment adopts an external cylinder-type clamping mechanism, which effectively prevents internal air leakage caused by damage to the sealing ring due to long use. The meter clamping device of this device uses three optical axes as positioning points, and the optical axes are installed To the stainless steel fixed plate used for wire cutting production, the coaxiality is good.
The front and rear straight pipe sections are made of POM material with a very small coefficient of thermal expansion and contraction, and the slider is processed in one step using a CNC machining center.
The device adopts a single-row reversible meter clamping mechanism driven by a servo motor. The flipping of the meter clamping mechanism is beneficial to the vacuuming effect of the wet water meter, eliminating air bubbles and water stains on the dial, and at the same time increasing the acquisition success rate of image recognition.
3) Flow regulating device
The device is equipped with three flow point pipelines and uses two electromagnetic flowmeters as flow indication devices. Below 250L/h, DN2.5 caliber electromagnetic display is used, and above 250L/h, DN25 electromagnetic display is used. It is equipped with three flow point pipelines, which are used to adjust Q3 respectively. \Q2\Q1 flow point.
During automatic detection of the device, the software automatically adjusts and detects the required flow points based on the flow range, pump frequency, valve opening, and other parameters set by the control parameters. Each flow point is equipped with a pneumatic ball valve to control which electromagnetic flowmeter to use. , when the software detects that the current flow rate does not match the set flow rate, the software automatically controls the water pump frequency or the opening of the pneumatic control valve to adjust the required flow rate.
When the detected flow rate is within the range of 500L-8000L, the device can be equipped with a Samson pneumatic regulating valve with a flow adjustment accuracy of <2%. When the detected flow rate is below 500L, a piston is used to automatically push out a stable flow rate.
4) Standard device
The standard device adopts a combination of piston and electronic scale. When the flow is ≤500L, the piston is used as the standard to provide flow. The high-speed counter collects the displacement pulse of the grating ruler to measure the standard volume. When the flow is >500L, the water pump provides the flow.
The electronic scales and electromagnetic flowmeters of the device adopt internationally renowned brands. The device uses METTLER TOLEDO's 120KG/6000E electronic scale as the standard instrument. Electronic scales of different brands and accuracy can be selected according to the size of the water meter tested. The electronic scale is independently installed on the outside of the main body of the equipment, which reduces the error caused by the vibration of the equipment to the electronic scale and facilitates the calibration of the electronic scale.
The basic working principle of the piston system is to compare the volume flow rate of the fluid discharged by the piston within a certain time interval with the volume flow rate of the flow meter being tested. The volume of fluid discharged by the piston is obtained by multiplying the cross-sectional area of the piston cylinder and the piston displacement; the piston is Driven by a 22L Panasonic servo motor, the top of the piston is equipped with a temperature sensor with Class A accuracy and a measuring range of 0-100°C and a Hangzhou Miko pressure sensor with an accuracy of 0.5%. It is used to measure water temperature and water pressure and compensate for the piston bore error. Equipped with a German ELGO grating ruler to measure the displacement of the piston and improve the accuracy of displacement measurement.
The active piston liquid flow standard device is shown in the figure above and mainly consists of a frame, piston rod, piston cylinder, motor, ball screw, supporting optical axis, sensor, protective shell, etc.
The piston rod is in close contact with the piston cylinder through the Y-shaped sealing ring. The three together form a sealed cavity. The movement of the piston rod is realized by the servo motor, coupling, ball screw, supporting optical axis, etc. The piston rod and the ball screw are The rod is connected through a screw nut, and the movement direction is controlled by a servo motor and a ball screw. A water suction pneumatic valve and a drainage pneumatic valve are installed at the outlet of the piston cylinder. The water suction pneumatic valve is connected to the water tank, and the drainage pneumatic valve is connected to the meter inspection pipeline. There are Install high-precision temperature and pressure sensors and install limit protection switches.
The core parts of the active piston liquid flow standard device are the piston rod and piston cylinder. Under the condition of ensuring sealing, the product of the outer diameter volume of the piston rod and the horizontal movement distance of the piston rod is the standard cumulative flow rate given by the device. Therefore, the processing accuracy of the piston rod, the sealing between the piston rod and the piston cylinder, and the accurate detection of the piston stroke within the calibration time period are the core of the device design.
Active piston devices can be divided into two categories: piston type and plunger type according to their structural forms. The piston type is in close contact with the piston cylinder through a sealing device, and the inner diameter of the piston cylinder is used as the measurement standard. Therefore, the inner wall of the piston cylinder needs to be finished, and the roughness of the inner wall and the roundness of the cylinder also have strict requirements. However, due to the influence of the length and diameter of the cylinder, it is difficult to process the inner wall of the piston cylinder, and the machining accuracy is difficult to guarantee. The plunger type uses the outer diameter of the plunger as the measurement standard, so the machining accuracy of the plunger is required to be higher. Nowadays, the machine The level of processing can ensure very good roundness and surface tolerance for the outer diameter of the plunger. The plunger type has a simple structure and a relatively reliable seal. The sealing ring is installed at the entrance of the piston cylinder for easy replacement. The form of the piston liquid flow standard device designed by the device is a plunger piston standard device.
Why choose an automatic water meter test bench with a piston device?
1. Stable flow and high calibration accuracy
2. There is no start-stop effect, and a stable flow rate can be achieved in 1S.
3. The clamping table has high concentricity and no air bubbles.
4. Automatic meter inspection, one-click operation
5. Piston automatic calibration system
6. Safety protection measures
7. No temperature is generated, the water temperature is constant
5) Commutator device
The device uses a flip-plate commutator as the flow-switching device. The commutator uses a rotating cylinder, which has the advantages of small vibration and fast switching speed. The uncertainty of the commutator is better than 0.05%. The commutator has been installed tested and calibrated at the factory. Photoelectric sensor, the user can switch at any time through the switch. The software of this device has the uncertainty detection function of the commutator transit time method. The user can detect the uncertainty error of the commutator by himself through the software during use.
The commutator adopts a rotating cylinder T ≤50ms, U4≤0.05%
6) Image acquisition system
What are the advantages of image acquisition systems?
Advantage 1: The image collection range is wide and no special alignment is required. As long as the dial pointer is within the range of the collected images, it can be recognized.
Advantage 2: It can be verified twice. After the test is completed, the software will automatically save the initial value and final value photos. If you have any objection to the test results of a certain table, you can query and save the pictures for review.
Advantage 3: High collection accuracy, collection error is within 0.001L
Advantage 4: Easy to install. The camera uses a POE-powered Ethernet industrial camera. It only needs one network cable to connect to the switch and the switch network cable to the computer network port.
7) Software control system
7-1) Software control system - hardware part
The control system mainly consists of industrial computers, PLC control systems, servo motors, grating rulers, various temperature and pressure sensors, pneumatic ball valves, platform software, etc. Industrial computers have strong anti-interference properties, which can make the calibration process more stable and reliable; PLC and servo motors are from internationally renowned brands with high precision and reliability.
Sensor:
The main sensors include a temperature sensor and a pressure sensor, which are located at the outlet of the piston cylinder. They are used to measure the temperature and pressure of the liquid respectively, and then transmit the information to the PLC and software system in a timely manner.
Sensors are important components for collecting analog quantities such as temperature, pressure, humidity, etc. Their accuracy and performance will directly affect the accuracy of the device's measurement results. Therefore, it is necessary to comprehensively consider various factors and select the most cost-effective sensor product. In this device, the temperature measurement range of the temperature sensor is (0~100)ºC, and the accuracy level is not less than 0.1℃; the pressure measurement range of the pressure sensor is (0~1.6)MPa, and the accuracy level is not less than 0.2% level.
Grating ruler:
The standard cumulative flow rate of the active piston liquid flow device is the product of the internal cross-sectional area of the piston and the piston displacement within the time period. Therefore, accurate measurement of the piston displacement is one of the key factors to reduce the uncertainty of the device. In order to improve the accuracy of displacement measurement, this device uses a grating ruler to measure the displacement of the piston. The output signal of the grating ruler is an AB orthogonal signal, which is improved by 4 times based on the original accuracy.
Servo motor:
The driving element of the servo system is a servo motor. The servo motor converts the voltage signal into torque and rotational speed to drive the control object. Changing the voltage signal can change the rotational speed and steering direction of the servo motor. Servo motors have the characteristics of large starting torque, wide operating range, no rotation, and high positioning accuracy. They are widely used in various automation control systems. Compared with stepper motors, servo motors have the following advantages:
1. Higher control accuracy;
2. It has good low-frequency characteristics and will not vibrate at low speeds;
3. It has different torque-frequency characteristics. It can output rated torque within its rated speed and constant power output above the rated speed;
4. It has strong speed overload and torque overload capabilities, and the maximum torque is 2~3 times the rated torque;
5. The servo drive system is a closed-loop control. The driver can directly sample the motor encoder feedback signal, and internally constitutes a position loop and a speed loop, making the control performance more reliable; the rotational inertia of the rotary body part of the shaft, kg·cm2
6. The AC servo system has good acceleration performance and can be used in control situations that require quick start and stop.
Reasonable selection of servo motors is the key to designing a motion control system. During design, all requirements must be fully considered in order to give full play to the performance of the servo motors.
Speed matching. The selection of a servo motor should first ensure that the stroke speed of the device does not exceed the rated speed of the motor. In order to make full use of the power of the servo motor, the stroke speed should be as close as possible to the rated speed of the motor.
Torque matching. The rated torque of the servo motor must be greater than the maximum torque of the load, but there is no need to leave too much margin because the maximum torque of the servo motor is generally 2 to 3 times its rated torque. The torque calculation formula of the device is:
F——axial load, N;
L——screw lead, m;
η——mechanical efficiency;
i——transmission ratio
The moment of inertia of the load needs to match the inertia of the servo motor. The large moment of inertia leads to large mechanical constants of the system, reducing servo accuracy and response speed. Therefore, during mechanical design, the moment of inertia should be minimized without affecting the stiffness of the system.
Jd = J L + J S
JL——The moment of inertia of the moving parts converted to the motor shaft, kg·cm2;
JS——Moment of inertia of the rotary body parts converted to the motor shaft, kg·cm2
PLC control system
The PLC control system of this device adopts Siemens S7-200smart system, uses ladder diagram programming language, and mounts analog input and output modules to collect and control temperature and pressure signals.
7-2) Software control system - software part
The software of this device is written in VISUAL STUDIO C# and uses the Microsoft ACCESS database. The detection process can be written into the database, and users can modify the control process according to different permissions. The software has an automatic meter reading function, which can be added to the software according to the user agreement to realize the collection of water meters and automatic correction of errors. After the detection, the error data is automatically saved to the database, and users can query the error data at any time.
Parameter settings:
Used to modify control parameters. According to national calibration regulations, instruments need to detect multiple flow points during the flow detection process. The parameter setting screen can add instrument parameters of different specifications and models according to user needs. After the addition, the data is saved to the database for the next time. When using, directly select the added specifications and models to call the instrument parameters added at that time.
Automatic detection program:
After setting the control parameters, click Auto Detection to enter the automatic detection program. The program runs according to the calibration point set by the control parameters. Before automatically detecting the flow point, the program will perform vacuuming, air bubble removal, and pressure suppression procedures. If these are not required, To operate, just turn off the corresponding switch in the instrument parameters.
Alarm display:
On the right side of the detection screen is the status display area. The running status information displays the current running distance of the piston and displays parameters such as temperature and pressure so that the user can understand the piston's operation in real-time. The software is set with multiple alarm prompts, such as a piston limit switch alarm, high-temperature alarm, high-pressure alarm, low-air pressure alarm, etc. You can view the alarm information and alarm level on the touch screen human-computer interaction interface, and solve the fault according to the instructions. When communication is normal, the indicator light in the communication status bar displays green. When communication fails, the indicator light of the corresponding device displays red.
Data query management:
Data query currently includes traffic original record and traffic certificate record data query. Users can query the detected data according to different query conditions. Users can print the queried data in report form according to their needs.
Report management:
The software is equipped with an open user report system, and users can edit calibration certificates and calibration records according to their own needs. Just write specific characters in the position of the variable that needs to be inserted, and the software will automatically insert the variable value.
This automatic testing platform adopts fully automatic control, fully automatic detection, and intelligent data processing and statistics. It has high meter inspection efficiency. It is driven by a servo motor to reduce the disturbance to the liquid flow, effectively solve the interference of water mist and bubbles, and has high calibration accuracy. It has the following characteristics :
1. Compared with traditional manual calibration devices, the operation is simple, and the computer calculates errors throughout the process to avoid human factors;
2. Improve the efficiency of meter inspection. The original manual meter inspection device takes 30 to 40 minutes to inspect a batch of water meters, and the upgraded automatic water meter inspection device only takes 5 to 8 minutes to inspect a batch of water meters. The meter clamping pipeline adopts an external cylinder-type clamping mechanism, which effectively prevents internal air leakage caused by damage to the sealing ring due to long use. The spacing can be adjusted according to the length of the meter, and inspection meters of various specifications can be clamped;
3. Save energy, water, electricity, and labor; small size, space-saving, fully automated, shared network, saving auxiliary materials. The flow adjustment device can automatically adjust and detect the required flow points according to the flow range, pump frequency, valve opening, and other parameters set by the control parameters. Each flow point is equipped with a pneumatic ball valve to control which electromagnetic flowmeter to use. When the software detects that the current flow rate does not match the set flow rate, the software automatically controls the water pump frequency or the opening of the pneumatic control valve to adjust the required flow rate;
4. The data management function is strong. The software can automatically complete the entire inspection process and draw calibration conclusions. It can save all water meter calibration data and has perfect functions such as calibration record query, correction, statistics, and printing. The camera direct reading acquisition method uses a POE camera and only needs one network cable to connect to the switch, and the switch network cable to the computer network port. The image collection range is wide and does not require special alignment. As long as the dial pointer is within the range of the collected images, it can be recognized. It can be verified twice. After the test is completed, the software will automatically save the initial value and final value photos. If you have any objection to the test results of a certain table, you can query and save the pictures for review. The collection accuracy is high, the collection error is 0.001L, and it also supports M-BUS, RS485, and other communication interfaces;
5. The structure is novel, the appearance is high-end, the industrial design and aesthetics are integrated, and the hardware and software complement each other, which can make the calibration process more stable and reliable;
S.H.Meters has rich technical experience, digs deep into product upgrades and process innovation, and pays no attention to every detail. While ensuring excellent product quality, we also ensure your production efficiency. Advanced equipment, rich experience, and excellent reputation will protect your production and are your best choice.
Device configuration selection table
Mainstream calibration
electronic scale
Flow range (m³/h)
0.002-6.3
Water pump
Nanfang pump 2.2KW/100H/8m³/h
Maximum working pressure (bar)
16
Number of water meters to be inspected
DN15(165mm)*10 pieces
DN20(195mm)*10 pieces
DN25(225mm)*8 pieces
Flip watch platform
No
Piston specifications
volume 22L/resolution 0.036ml/pressure PN16/Panasonic servo drive
Electronic scale
Toledo 120KG/6000E
Weighing container
120L
Electromagnetic flowmeter
YokogawaAXG/DN2.5+DN25
Commutator
DN25
Temperature sensor
PT100, accuracy level A, installed at the inlet and outlet
Pressure sensor
Hangzhou Miko pressure transmitter, accuracy 0.5%, installed at the inlet and outlet
Test method
start-stop method + commutator method
Standard signal interface
MBUS/485/infrared
Equipment power
10KW
Water and electricity
users provide AC400V three-phase five-wire power supply/purified water/6bar air pressure
Quote
Contact us
In this guide, you’ll find everything you need to know to get started with water meter testing programs, including:
All mechanical utility meters (water, gas, electric) will decrease in accuracy over time. Water meters from 5/8” to 2” in size leave the factory with a measurement accuracy of 100% +/- 1.5% registration as per AWWA standards. Positive displacement meters which are typically used in residential and light duty commercial settings do not over register by design and cannot be calibrated. Water meters in general tend to register less usage (slow down) as they get older. Over time mechanical water meter accuracy can be affected by three main components:
The practice of statistical sample testing of water meter populations has been around for quite some time and is also used in the gas and electric meter industry as well. It involves the testing of meters that are a randomly selected from the overall meter population. The batch of meters selected is generally a statistically relevant sample size such that the number of water meters chosen will properly represent the overall population of meters. Sample testing is important because the tests results of the group of meters selected will help a utility to map out a meter replacement strategy for the remainder of the metering system.
Sample Batch Test In Progress
The American Water Works Association (AWWA) is the current standard for cold potable water meter use in North America to date. Measurement Canada (MC) enacted legislation in 1985 that governs the units of measure used in Canada for the custody transfer of products. MC has the right to regulate any measuring device such as weigh scales, gas pumps and even utility meters. Currently MC regulates natural gas and electric meters in Canada and have chosen to leave water meters as status quo. This means that water utilities throughout North America continue to do what they have been doing for the last 120 years which is to self-regulate water meter sizing, selection, testing, and replacement cycles based on the AWWA standards.
The benefits of statistical meter sampling for water purveyors are:
Typically, water billing is the second largest component of a municipality’s cash register next to tax revenue. This makes it super important for water utilities to keep the water meters as close to a hundred percent accurate for as long as possible. As water meter accuracy declines over time so does the annual water budget revenue. In most cases a cost justification can be made to replace the water meters on new meter revenue increase alone.
Starting a dry meter on the low flow test may lead to false representation of actual low flow accuracy. It is recommended that after removal from service that water meters be capped at each end with a small amount of water left remaining in the meter. Starting at the highest flow rate helps the meter to acclimate to measurement again since the meter may have been sitting for a couple of weeks between removal of service and arrival at test facility.
Test rates vary by meter size however all meters are tested at a minimum of three flow rates high, intermediate, and low. Water demand in a home is not constant, so testing at different flow rates gives us a better representation of the meter’s overall or weighted average accuracy.
All water meters decline in accuracy over time due to water quality factors such as turbidity and hardness as well as years in service, including amount of consumption metered. Positive displacement water meters are typically designed to sustain reasonable accuracy over a 20-year period. Historical test data shows us that we can expect somewhere between 3-5% accuracy decline within this period mostly occurring in years 15-20. Since a considerable amount of residential consumption occurs at low and intermediate flow rates much of the accuracy decline throughout the meter’s installation period will occur at these rates. Meters beyond 20 years old can expect test results to show accuracy decline anywhere between 5-10%.
Know your water meter system! A water meter database is only as good as the quality of data entered into it. Some practices to consider when creating an overall testing plan:
Sample Batch of Aged Meters For Testing
Most statisticians will agree that 100 water meters would be the minimum sample size for any meaningful data conclusions. Many say that the maximum would be 10% of your meter population (up to 1,000 meters) would be the maximum representative sample. Going above 1,000 meters tested won’t add much to the accuracy profile you are creating and would add significantly to the meter testing budget.
Bottom line is that there is no perfect plan, start somewhere as it’s better than not starting at all. If uncertain about the best approach, contact an industry professional for a consultation. It will help you to determine the best overall fit for your requirements.
Evans Supply Limited helped the City of Port Colborne’s business case to replace 6,000 water meters twenty years after their original installation. The city removed 170 water meters from their system and testing determined that 40% of the randomly selected batch were not registering accurately. The meter test results played an important role in their business case to replace their aging water meter population.
Start building your meter test database today. Whether you’re replacing a meter for a technology upgrade or any other work order, don’t scrap the meter immediately. Set it aside for batch testing. Once you’ve accumulated a box or two send it to your local test facility. Over the duration of your meter population life cycle, you will have accumulated test data that fairly represents the state of your system. This data will enable the utility staff to confidently justify their meter replacement line item in the budget. Get in contact with us today to arrange for some sample testing!