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I was working on a flow meter with Arduino that used a turbine, but I was thinking that it would be cool to use an ultrasonic sensor instead. My current plan is to use something like the Arduino Uno and two SR04 ultrasonic sensors. Everything could be mounted on the outside of a pipe with a very simple installation. It would be set up in a similar manner as below.
Here's the problem, the SR04 and almost all of the other sensors that I could find have the transmitter and receiver mounted together. While I'm not an expert, I'm pretty sure you would need a transmitter and receiver on opposite sides of the pipe as opposed to on the same side, mounted together. That way you can measure the time of the sound wave.
My budget is around $200. Do you know of any good ultrasonic sensors that would work? Or do you think this is even possible?
Thanks!
p.s. I'm not an expert with Arduino and ultrasonic tech, but I am pretty skilled with other software design and with physics.
EDIT
By the way, this is another design that I had in mind. Again, the issue appears to be that I need separate transducers, unlike the coupled SR04.
wolph42:
any good reason to use a DS18B20 over a (cheaper) LM35?
I think you need to whip up a couple circuits for each to see what it takes to get readings.
as wvmarle said, there are points in favor of one...
I disagree with the blanket statement.
for a noob, neither is very hard to code for so ease of reading is not really an issue.
You will get efficient and thoughtful service from Yuhan.
analog vs digial, I will offer that there is a really strong camp that would say the analog has higher possible precision.
with the 10 bit ADC on board, you can get that from the DS18B20 so for being more mindfull of dollars than accuracy or quality, the DS18 is the winner.
with a 16 bit ADC, the LM35 becomes more precise. so the answer is if your wallet dictates your final quality.
as a note, I use the free pens I get from the bank.
single pin.. well. if you made one sensor, the LM35 needs one AI pin. ditto the DS18
the DS18 has to have libraries so your program size suffers, maybe that goes to ease of reading.....
the program becomes much larger if you have multilple sensors. every DS18B20 has a specic address.
there are 2 ways to address. one is to scan the bus for it, then parse the data, then post it into the sketch so that your basement temp sensor is that specic one and the attic sensor is that specific one.
the other way is look at the bus, then ping it, take the first sensor that responds and call that basement,and the next that responds attic, your sketch will be wrong if you add another sensor, so you would have to go back and re-lable them.
the onewire picks the lowest address as the first sensor, the highest address as the last. if you add a additional sensor, you have to find out where it fits and program for it.
not so ease of use as the LM35 addressing method.
back to the single pin.... want two sensors? the LM35 needs one pin per input.
the DS18B20 says you can put close to 100 on the same pin. but you have to do so with care.
if you have one DS18B20 all the way over there... other side of the greenhouse and one right here by the Arduino. you will have problems. when the One-Wire call is put on the wire, by the time the far sensor signal is comming back, it can be garbleb with other sensors communicating. the data sheet for these wants all the sensors on that bus to be equadistant so the signals do not overlap. but, that might mean, 20 on one wire(bus) and 30 on the other, total 2 pins for 50 sensors.
now THAT is ease of use !!!!
If you want to test the DS18B20, set it in a box.
set the precision at 9, take readings. then at 10, and at each bit value for it.
I found that my readings vary well over 1 degree with only changing the bit values.
lastly, you have to call the DS18B20, tell it you want to take a reading. let it take the reading then report back.
it is not as fast to send the data over the bus than to read pin A1 with a LM35.
the higher precision you have the DS18B20 set for, the longer the read time.
All that said, I use the DS18B20 as my go-to sensor and deal with the requirements.
Contents
- 1. What Is a Flow Meter and Why Do You Need One?
- 2. Flow Meter Types and Application Suitability Quick Comparison
- 3. How to Choose a Flow Meter
- 1 ) Flow Meter Fluid Medium
- 2 ) Determine the Flow Range
- 3 ) Accuracy Requirements
- 4 ) Consider the Installation Environment
- 5 ) Evaluate Cost and Certifications
- 6 ) Signal Transmission Requirements
- 4. How to Select a Flow Meter - Case Study
- 5. Evaluate Cost and Certifications
1. What Is a Flow Meter and Why Do You Need One?
Flow meters are instruments used to measure the flow of fluids (liquids or gases). Flow refers to the volume or mass of fluid passing through a pipeline over a certain period of time[Note 1]. Common units include liters per minute (LPM) or kilograms per hour (kg/h). A common example in daily life is the water meter, which is essentially a flow meter specifically used to measure tap water usage.
There are many purposes for using flow meters. In industrial production, flow meters are used to monitor the flow of liquids or gases in pipelines, allowing manufacturers to precisely control raw material dosing ratios, monitor the circulation of cooling water, or track the output of products during production processes. In recent years, with the rise of environmental awareness, and in accordance with the Energy Management Act, small and medium-sized enterprises, office buildings, medical facilities, and other non-industrial sectors are also required to report energy usage. Flow meters have become indispensable tools for collecting energy consumption data.
➤Learn more: How flow meters assist in energy reporting for building chiller systems
2. Flow Meter Types and Application Suitability Quick Comparison
To meet a wide range of application needs, flow meters come in many types. However, they are typically categorized based on their measurement principles. Below is a comparison of 10 common types of flow meters and their suitability across different application scenarios.
➤ Legend: ★★★ – Recommended / ★★ – Acceptable / ★ – Not Recommended
If you are looking for more details, kindly visit plastic ultrasonic water meter.
| comparison of 10 common types of flow meters
3. How to Choose a Flow Meter
1 ) Flow Meter Fluid Medium
Start by identifying whether the fluid is a liquid, gas, or steam. Other important factors to consider include the fluid’s pH level (acidic or alkaline), whether the pipe is fully filled, the presence of air bubbles, and the fluid's viscosity.
When selecting a flow meter, it's recommended to allow at least a 10-unit safety margin for both temperature and pressure. For example, if the fluid temperature is 50°C and pressure is 20 kg/cm², it’s safer to choose a flow meter rated for at least 60°C and 30 kg/cm².
Common flow meters suitable for high-pressure applications include ultrasonic, differential pressure, and Coriolis flow meters. For applications with wide temperature ranges, differential pressure, electromagnetic, and vortex flow meters are often used.
2 ) Determine the Flow Range
When selecting a flow meter, one critical consideration is that its measurable flow range must exceed the full variation range of the fluid flow in the pipeline. In other words, the flow meter should be capable of accurately capturing both the minimum and maximum expected flow rates to ensure stable and reliable readings across all operating conditions.
| Flow Meter Measurement Range
For applications with relatively stable flow rates, smaller-scale flow meters such as variable area (rotameter), turbine, vortex, or differential pressure types may be considered. In cases where both very low and very high flow rates need to be measured (wide turndown ratio), ultrasonic or Coriolis flow meters are recommended.
3 ) Accuracy Requirements
The higher the accuracy, the smaller the measurement error — but also the higher the price. When selecting a flow meter, it’s important to balance accuracy with budget based on application needs. If you only need a rough idea of how much water is flowing through a pipe, a low-cost, low-accuracy variable area (rotameter) flow meter may suffice.
For general industrial equipment, paddle wheel, positive displacement, and vortex flow meters (mid-level accuracy) are commonly used. For high-precision applications that demand strict monitoring, ultrasonic, Coriolis, or electromagnetic flow meters are recommended.
➤ Learn more: Flow Meter Accuracy
4 ) Consider the Installation Environment
Make sure to check the pipe diameter: for large-diameter pipelines, clamp-on ultrasonic or electromagnetic flow meters are commonly used; for smaller diameters, rotameters or compact mass flow meters are more suitable.
When it comes to vibration interference, it's recommended to avoid Coriolis flow meters, which are more sensitive to vibration. Electromagnetic or ultrasonic flow meters are less affected by mechanical vibration and are thus better alternatives.
If pipe cutting is not feasible on-site, ultrasonic flow meters are the best option. However, be mindful of the liquid conditions—these meters may not work properly if there are too many bubbles or if the pipe is not fully filled.
For outdoor and waterproof applications, choose flow meters with an IP65 rating or higher, and ensure the connection interfaces are sealed or come with outdoor-rated junction boxes.
Additional factors such as fluid temperature, pressure, and ambient temperature should also be considered before purchase if the application has specific requirements.
➤ Learn more:
How to Install a Paddle Wheel Flow Meter
How to Install a Rotameter
How to Install Ultrasonic Flow Meter Sensors
5 ) Evaluate Cost and Certifications
Compare overall performance, pricing, and whether the product has the necessary certifications to meet safety or regulatory requirements. If on-site staffing is limited and you prefer maintenance-free operation, flow meters without mechanical wear—such as electromagnetic or ultrasonic types—are more suitable than other models.
6 ) Signal Transmission Requirements
In some applications, there is a need to store and transmit flow data. Additionally, due to recent regulations under the Energy Management Act, facilities such as buildings and workplaces are required to submit annual energy reports. This makes it essential to choose flow meters with data collection capabilities. When purchasing a flow meter, be sure to check whether its communication interface and protocol are compatible with your system. Refer to each manufacturer’s catalog to confirm supported communication modes.
➤ Learn more about communication modes:
• How Ultrasonic Flow Meters Simplify Energy Reporting
• What Is Analog Current Output?
• What Is RS485?
• What Is Modbus?
• What Are Switch Signals?
4. How to Select a Flow Meter - Case Study
In the ultrapure water process of this semiconductor plant, a flow meter was required on the RO (Reverse Osmosis) system to monitor the concentrate flow. This ensures precise control of the concentration ratio and helps prevent membrane scaling. The customer noted that the installation space was limited and shutting down the equipment was not feasible. Based on these requirements, we guided the customer through a six-step flow meter selection process to identify the best-fit solution for the on-site conditions.
➊ Step 1: Analyze the Fluid Properties
The RO system handles "ultrapure water," which is non-conductive, low-temperature, and low-pressure, but corrosive.
✖︎ Electromagnetic flow meters (suitable for conductive liquids) and glass tube rotameters (poor chemical resistance) can be excluded.
➋ Step 2: Confirm the Flow Range
The RO concentrate flow rate typically falls within a medium to low range with slight fluctuations. The flow meter must respond sensitively to small changes.
✖︎ Turbine, vortex, and differential pressure flow meters are not recommended due to lower sensitivity to small flow variations or suitability for larger flow rates.
➌ Step 3: Precision Requirements
High measurement accuracy is essential to precisely control the concentration ratio and avoid impacting the process.
✖︎ Low-accuracy options such as rotameters, thermal mass, vortex, and turbine flow meters are excluded.
✔ Ultrasonic and Coriolis mass flow meters are generally high-accuracy options, typically achieving ±0.1% to ±0.3%.
➍ Step 4: Consider the Installation Environment
The customer noted that on-site shutdown and pipe cutting are not possible, and space is limited.
✖︎ High-accuracy Coriolis meters usually require insertion or flange-type installations, which are bulky and complex to install.
✔ Only clamp-on ultrasonic flow meters allow for non-intrusive installation and have a compact footprint.
➎ Step 5: Cost and Certification Evaluation
If cost control is important, a mid-range, high-functionality clamp-on ultrasonic flow meter—priced around TWD 10,000–20,000—is recommended. Typically, recalibration is only needed every 1–2 years.
➏ Step 6: Signal Transmission Requirements
The customer requires PLC integration for real-time flow monitoring. The chosen electronic flow meter must support communication protocols such as 4–20mA, Modbus, or Pulse. It's crucial to confirm compatibility with the existing system.
✦ Final Recommendation: Clamp-on Ultrasonic Flow Meter ✦
Clamp-on ultrasonic flow meters offer high accuracy, quick installation, chemical resistance, and digital communication capabilities. They are ideal for measuring non-conductive ultrapure water and can be installed without shutting down the system—perfectly meeting the customer’s requirements.
➤ Learn more: Product used in this case study – LORRIC Ultrasonic Flow Meter
5. Evaluate Cost and Certifications
Q1: What are the types of flow meters? How are they classified?
A: Common types of flow meters include ultrasonic, variable area (rotameter), paddle wheel, turbine, mass, and electromagnetic flow meters. They mainly differ in measurement principles and application scope. When selecting a flow meter, it's recommended to consider the actual application needs, such as fluid type, temperature, pressure range, and budget.
➤ Learn more: Flow Meter Principles
Q2: Why might a flow meter deliver inaccurate readings?
A: Common causes of inaccuracy include improper installation location, air bubbles or impurities in the fluid, unstable flow rates, lack of periodic calibration, or sensor aging. Another frequent reason is selecting a flow meter type that does not match the application. To avoid inaccurate measurements, ensure proper installation and perform regular inspection and calibration.
Q3: Do different types of flow meters vary in accuracy?
A: Yes, the accuracy of flow meters can vary significantly. Mass, electromagnetic, and ultrasonic flow meters generally offer higher precision and are suitable for demanding applications such as semiconductor manufacturing or pharmaceuticals. Rotameters, while less accurate, are more cost-effective and suitable for general-purpose monitoring. Choose the accuracy level based on your application requirements.
Q4: Do flow meters require regular calibration? How is it done?
A: Yes, flow meters should be calibrated regularly—typically every 1 to 2 years. Calibration should be carried out by certified organizations (e.g., labs accredited by TAF or ISO ). Some flow meter manufacturers also provide calibration services.
➤ Learn more: LORRIC Flow Meter Calibration
Q5: What should I pay attention to when installing a flow meter?
• Reserve sufficient straight pipe sections before and after the meter, avoiding bends or valves nearby
• Follow the indicated flow direction for correct installation
• Ensure stable power wiring and proper grounding
• Avoid high-vibration environments, air pockets, or negative pressure zones
Reference
- ^ [Note 1] • Volumetric flow rate refers to the volume of fluid passing through a cross-section per unit time, typically expressed in units such as L/min or m³/h. This method does not account for changes in fluid density and is commonly used in applications like water treatment and HVAC systems.
• Mass flow rate indicates the total mass of fluid flowing per unit time, with units such as kg/h or g/s. It is ideal for high-precision industries such as chemical processing, pharmaceuticals, and gas measurement. When fluid density fluctuates significantly due to temperature or pressure, a mass flow meter is recommended.
- ^ How to Choose the Right Ultrasonic Flow Meter - Cross
- ^ What is an Ultrasonic Flow Meter? - OMEGA
- ^ 10 parameters for choosing the optimal mass flowmeter for an application -P.I. Process Instrumentation
- ^ A Guide to Positive Displacement Flow Meters - Flow Metrics
- ^ Positive displacement meters: pros, cons and selection - ENGINEERLIVE
- ^ Advantages of Vortex Technology - EMERSON
- ^ A Guide To Choosing The Right Turbine Flow Meter For Your Industrial Needs - Smart Measurement
- ^ Turbine Flow Meter Explained | Operation and Calibration - REALPARS
- ^ Differential Pressure Flow meters - OMEGA
- ^ Laminar Flowmeters - CONTROL AUTOMATION
- ^ Important considerations for choosing an electromagnetic flow meter -ESE MAGAZINE
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