Tag Archives: Scientific Products

Buy a Customized Mass Flow Controller Online!

After reading Kam’s last post about how Sierra’s OEM and Custom Solutions Group can help you customize a flowmeter for your application, I got inspired to share a way you can custom configure our mass flow controllers and actually buy the flow meter online.

Lets say you need a SmartTrak 100 digital air flow sensor for Argon with a max flow range of 28 slpm. Our selection wizard lets you enter this configuration and properly sizes the instrument for you.  In addition, you can then choose all the options you may want – digital display, fitting size, elastomer type, output signals and more. The selection wizard assembles the proper model for you and prices it out. From there, you can buy it if you want.

Shop for a Smart-Trak 100 online and buy it today!

https://www.youtube.com/watch?v=ivSDSOQ_iqs

New Video: Best Cabling Wiring Connections, Power Options

Interestingly enough, our technical support team gets more questions about the compatibility between our power supplies and cabling options than any other installation question. This, as you know, is an important step to getting your MFC up and running-and providing you with accurate air flowmeter measurements—in no time. In recent weeks our, Technical Support Supervisor, Jim Oswald, has walked you through unpacking, set-up and leak testing of your new MFC. In our latest video, Jim details power supply and wiring connections and your options for powering your mass flow controller

As Jim explained, depending on the needs of your application, you will choose different cabling options for your Mass Flow Controller, and it really depends on your particular application. To make the process even easier, Sierra has the right cabling options for you to purchase online for fast delivery. Have further wiring-related questions? Jim mentioned our Quick Installation Guides for each product which you can find in our documents and downloads section or our power supply & cabling guide.  As always, don’t hesitate to contact us!

We want to know: What are your most common application questions? Use our live chat to get answers real-time.

Perfect Beer Foam with Modern Flow Meters

We talk a lot about the use of flow meters in flare gas, waste water and sub-metering applications, but Sierra’s innovative flow meters are utilized by a wide variety of industries. You’ll find our flow measurement and control devices orbiting the earth, assisting with the creation of oceanic atmospheres in research facilities and even improving the brewing process in an ancient Trappist Monastery.

Orval Brewery is located within the confines of Orval Abbey, a several thousand-year-old Belgium Trappist Monastery. The current brewery was opened in 1931 to support the resurrection and reconstruction of Orval, and income generated from sales now goes to social welfare works and building maintenance.

In the past 15 years, Orval Brewery has completely modernized its brewing facilities. The food and beverage industry has struggled with obtaining highly accurate measurements in rugged factory environments. In 2006, Sierra partnered with Orval’s Brewery to help them modernize their process and create beer with a more stable foam.

Sierra’s MaxTrak 180 was the perfect choice to help them overcome the challenges in modernizing their facility. Already proven in a process by Heineken, the Sierra mass flow controller gently ads Nitrogen to what beer experts regard as liquid gold. The Dial-A-Gas capability is extremely valuable in achieving aeration during fermentation and the ultimate goal of the perfect head of foam. Precise accuracy and repeatability, remote monitoring, and rugged wash down protection make it indispensable in the brewing process.

Watch the video below to “visit” Orval’s Brewery, and see how the MaxTrak is an integral part of their brewing process.

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Read how Sierra flow meters and controllers in a variety of unique applications.

Core Technology Series: Capillary Tube Thermal Mass Flow Meters and Controllers

Understanding Capillary Tube Thermal Mass Flow Meters & Controllers:  

Flow meters and controllers are used every day in general purpose industrial and laboratory applications and in the semiconductor industry.  Have you ever wondered how capillary tube flow meters work?  or How to specify the perfect flow meter for your application? I am excited to present this ongoing core technology series based on excerpts from Sierra’s Founder and Chairman (Also my Father), Dr. John G. Olin’s, white paper entitled, “Capillary Tube Thermal Mass Flow Meters & Controllers- A User’s Guide.”  This “User’s Guide” is designed to educate both flow beginners and experts in the most common types of direct mass flow thermal flow meters, typical applications, principle of operation of capillary tube thermal flow meters, best practices for users, including the selection, installation, and operation of the instruments.   Now let’s start at the beginning.

What is a Capillary Tube Thermal Mass Flow Meter or Controller?

Capillary tube thermal mass flow meters directly measure the mass flow rate of clean gases and gas mixtures in lower flow ranges. A capillary tube thermal mass flow controller adds an integrally mounted flow control valve to the flow body of the mass flow meter and both monitors the mass flow rate and controls it to be equal to a set-point value selected by the user.

History of Capillary Tube Thermal Mass Flow Meter and Controllers

SmartTrak 100 flowmeter for highly accurate gas mass flow control

Capillary tube thermal mass flow meters and controllers were first commercialized in the early 1960’s. The space industry was one of the first users, but before long the industry that fabricated solid state semiconductor devices recognized their usefulness. When integrated circuit semiconductor devices began their long and continuing period of exceptional growth, the market for capillary tube thermal mass flow controllers grew with it. In the 1970’s and 1980’s, general industry recognized the advantages of using capillary tube mass flow meters and controllers in a broad range of applications, and several new companies were formed to serve this growing market. The advantages of accuracy, compactness, reliability, and cost-effectiveness continue to make capillary tube thermal instruments the choice for monitoring and controlling smaller mass flow rates of clean gases in general industry and in the fabrication of semiconductor devices.

The primary virtue, and the source of their prominence, is the fact that capillary tube thermal instruments directly measure mass flow rate, as opposed to, for example, volumetric flow rate. This is important because most industries need to measure and control the flow of the molecules, i.e., the mass, of the gas entering their process.

Types of Direct Mass Flow Meters & Applications

Figure 1: Classifications of Mass Flow Meters

There are two kinds of flow meters that directly measure the mass flow rate of fluids—Coriolis mass flow meters and thermal mass flow meters. Coriolis mass flow meters directly measure the mass flow rate of most fluids, both liquids and gases, and do not require knowledge of the identity, or composition, of the fluid. Thermal mass flow meters directly measure the mass flow rate of gases, and do require knowledge of its composition. Coriolis mass flow meters have high accuracy, high pressure drop, work best with liquids, and are relatively expensive. Thermal mass flow meters have medium to high accuracy, low pressure drops, work best with gases, and are relatively inexpensive.

For the purposes of this blog series we will focus on thermal mass flow meters. Specially, capillary tube flow meters and controllers. Capillary tube thermal mass flow meters and controllers have two broad fields of application: general purpose industrial and laboratory applications and semiconductor manufacturing and other high purity vacuum processes. More MFCs are manufactured than MFMs because most users want to control the mass flow rate of the gas in their process rather than just monitor it. Capillary tube thermal MFCs offer a cost-effective solution for controlling the flow of gases because they are compact, require only one penetration of the process line, and have a built-in optimized control system.

Principle of Operation: How Capillary Tube Mass Flow Meters & Controller Work

Figure 2: Typical general purpose mass flow controller

In the case of the capillary tube type of thermal mass flow meter (MFM) described in this blog, the flow enters the flow body and splits into two internal flow paths. One path flows through a heated capillary sensor tube that has a small diameter and relatively long length. The second parallel path inside the flow body passes through a split-flow bypass consisting of a laminar flow element that shunts the bulk of the flow around the sensor tube. The ratio of the flows through the bypass and the sensor tube is a constant. The capillary sensor tube measures its internal mass flow rate by means of the heat capacity of the gas that carries heat from an upstream resistance-temperature-detector winding to a downstream winding, both  on outside of the sensor tube. The difference in the electrical resistances of the two windings provides the measurement of the mass flow rate through the sensor tube, and thereby the total mass flow rate in the flow conduit.

A capillary tube thermal mass flow controller (MFC) adds an integrally mounted flow control valve to the flow body of the MFM and both monitors the mass flow rate and controls it to be equal to a set-point value selected by the user either remotely or on the MFC itself. To learn more about Capillary Thermal Mass Flow Controller & Meter technology, watch this video that follows a molecule of gas through a typical capillary thermal flow controller.

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Next up in the “Capillary Tube Thermal Mass Flow Meters & Controllers- User’s Guide” series, Dr. Olin describes the mechanical components of mass flow meters and controllers and the operation of these components.

Get more information on Capillary Tube Mass Flow Meters and Controllers:

Download Dr. Olin’s Complete White Paper “Capillary Tube Thermal Mass Flow Meters & Controllers- A User’s Guide.”

Read more about the History & Evolution of Mass Flow Controllers

Read Core Technology: Capillary & Immersible

 

For Complex Applications, Have Your Mass Flow Controller Adjusted Remotely

The days of simple analog mass flow meters with no variables but a zero pot are gone. Now you can get great flexibility with advanced digital mass flow controller technology like our Smart-Trak 100. But, because of this virtue, the flow meter also has many communication variables. We try to keep it simple by minimizing the need to access many of these variables in our customer communication program. However, sometimes your application is truly challenging and requires more adjustments than usual. To harness the true power of the instrument, you need more software and more knowledge.

That’s where our ability to remotely adjust a mass flow controller really comes in handy. If you have a Smart-Trak 100, here’s how you can take advantage of our remote programming services:

  • Connect the 100 Series flow meter to a computer using RS232 or open-source MODBUS RTU protocol.
  • Connect the computer to the Internet and contact Sierra Instruments.
  • Allow us to “take over” the computer  and the instrument remotely using TeamViewer or GoToMyPC and we will adjust the flow meter as required.

In applications where you need advanced air flow sensor capabilities, our Compod™ Programmable Control Module comes with multi-drop RS-485/MODBUS RTU communications, giving you full system control, monitoring and the ability to network multiple flow meters. You can add Compod to any of our 100 Series models, including the Smart-Trak 2, the next generation of our digital flow meters.

If you need more advanced help, training or support, you can contact us at info@sierrainstruments.com or by using live help.

Economic OEM Mass Flow Controller for PVD Applications

Those of you who work in the solar energy and semiconductor industry will be familiar with physical vapor deposition (PVD) or sputtering that is commonly used for creating films of material on a substrate in the solar energy and semiconductor industry.

In the PVD process, a negatively charged electrode is slowly disintegrated by molecular bombardment. The PVD medium is typically argon because this gas generates sufficient momentum to free atoms from the target. In a vacuum environment, these free target atoms deposit themselves on the surface of the material and form the desired coating or plating.

Maintaining a specified gas mass flow rate to the vacuum chamber is critical during the PVD process. Typically, vacuum pumping stations require a throttle valve or orifice-limiting device to control the pump’s output when the PVD gas is introduced. This method is extremely pressure sensitive and can result in inefficient gas delivery and poor product quality.

PVD presents two critical challenges in the manufacturing of films used in solar photovoltaics. The first is the use of high vacuum. Since there is so little pressure drop to work with, PVD processes require flow control devices that are relatively insensitive to the absolute pressure in the chamber. This rules out devices like orifice plates that require a large pressure difference to operate efficiently.

The second issue is maintaining very precise gas mass flow rates. Since the layers deposited by PVD processes can, in many cases, be only molecules thick, very precise delivery methods of the doping gases are required.

At Sierra Instruments, we are in tune with these challenges and offer a solution for both: the Smart Trak® 50 digital flow meter. The instrument automatically compensates for changes in system pressure (vacuum pump fluctuations) or loss of pressure from the gas source (cylinder depletion). The SmartTrak 50 delivers a precisely controlled gas mass flow rate to the vacuum chamber to maintain high quality end-product.

Whether you’re a machine builder, systems integrator or end-user, our family of economical/OEM mass flowmeters and mass flow controllers provide a comprehensive mix of flow solutions for nearly every application type.

Technical Resources: Power Supply and Cabling Options

Believe it or not, many times selecting the correct power supply and cable for your product is the most challeging part of specifying and installation. To make these decisions easy, we have the Technical Resources: Power Supply and Cabling guide to help you choose the best power supply and cable for your meter or controller.

This guide not only has descriptions but drawings to demonstrate each configuration (see figure 1 & 5 ). Having the right power supply and communication cables makes all the difference in obtaining accurate mass flow readings in the most efficient way possible. Read on to learn about the individual power supply products we offer for the SmartTrak 100 series, the detailed communication cable configurations, and the accessories that you’re sure to find invaluable as you begin to use your new mass flow controller.

Power Supplies for Mass Flow Meters and Controllers

Flow Meter Cabling Options

Fig. 1

  • 100-T8D. This two-lead, 24 VDC power supply with 15-pin D-connector is the simplest way to power your flow meter or controller and is compatible with all low-flow 100 series controllers and all sizes of our 100 Series meters. Display software is included to read the flow or provide a flow signal. See Fig. 1.
  • 100-T8F. Instead of a connector, this 24 VDC power supply has two bare fly leads that can be soldered onto the appropriate wires of one our communication cables. This power supply is compatible with low-flow 100 Series controllers and all sizes of meters.

Communication Cables For Efficient Flow Meter Measurement

Power Cabling Options

Fig. 5

  • 100-Analog Cable. This 15-conductor “do everything” cable features fly leads that allow you to create your own connection to your power supply, analog or digital output, control signals and your PLC. In addition to 1, 3, 10 and 25-foot lengths, this cable can be custom ordered to meet your flow meter measurement needs. See Fig. 5.
  • 100-RS232 Digital Cable. This 6-foot cable provides a simple 3-wire connection to your computer. Simply plug into the side of the SmartTrak 100, 101 or 140, and use the other 9-pin serial port connector to connect to your computer.

Accessory Options to Complete Your Ideal Flow Meter Setup

  • Serial to USB. If your computer doesn’t have a 9-pin serial port, this adapter easily converts the 100-RS232 Digital Cable referenced above to USB. See Fig. 5 above.
  • 15-pin Connector D-kit. If you prefer to construct your own cable for power and/or signals going in and out of your SmartTrack mass flow controller, then this connector set is for you!
  • Remote Pilot Module. This remote display/touchpad connects to the RJ45 socket and allows you to control your mass flow meter from up to 10 feet away.

As you can see, we offer an extensive line of power cabling options so that your Sierra mass flow meter or controller meets your specific requirements and environment. For all your gas measurement needs, be sure to browse our many product lines designed with accurate flow measurement in mind.

What are your most pressing questions about power supply and cable options?

4 Ways to Make Flow Calibration Easy for You

Flow Meter Service

Our flow experts here at Sierra are committed to ensuring your flow meter is accurately calibrated and returned quickly so downtime is kept to a minimum. Sierra’s latest flow meter service and calibration brochure, “Precision Delivered”, details that level of commitment, showcasing four key components of our approach to flow calibration service.

Assuring your flow measurement accuracy is always at the heart of all of our flow solutions and services. Sierra is ISO 9001 quality certified, with more than 40 primary standard flow calibration standards—all NIST traceable.

Flow Meter Service Brochure1. Easy Online Management System – Keeping track of calibration service due dates is easy when you create an account on our site. Handy email reminders let you know when your flow instrument is in need of calibration.

2. Calibration Management – Your service account manager provides you with a personalized experience, tracking the calibration progress from start to finish for fast, on-time delivery back to you.

3. On-Site Calibration – Need your flow meter calibrated the same day? Our technicians can schedule an on-site visit to calibrate your flow meter or controller with our CalTrak portable primary standard.

4. Global Flow Centers of Excellence – With more than 40 years of experience providing flow solutions, Sierra is uniquely positioned to provide accurate calibration and the timely return of your flow meter or controller. We currently have service and calibration centers in the USA, Mexico, Brazil, United Kingdom, The Netherlands, India, Singapore, China and South Korea.

You’ll see how convenient Sierra’s flow calibration service really is with your first calibration free. Download the latest service brochure today.

 

 

Core Technology Series: Major Components of Mass Flow Meters and Controllers

Have you ever wanted to look inside a mass flow meter or gas controller to understand the mechanical components? This blog, as part of our ongoing core technology series based on excerpts from Sierra’s Founder and Chairman, Dr. John G. Olin’s, white paper entitled, “Capillary Tube Thermal Mass Flow Meters & Controllers – A User’s Guide,”  dives “under the hood” and takes a closer look at the flow body, flow rates & sizing, and how flow conditioning works. 

Under the hood – The Major Components of a MFM & MFC

A mass flow meter (MFM) has five major components: flow body, flow conditioning section, flow sensor tube, bypass, and electronics.  A mass flow controller (MFC) has the same components as an MFM, but also has an integral control valve mounted on the same flow body as the MFM (See Figure 1).

SmartTrak 100 inside view

Figure 1.

The Flow Body

General purpose mass gas flow meters and mass flow controllers (MFC) typically have only three flow body sizes covering the entire flow range of the instruments: low flow, medium flow, and high flow. The gas flow ranges of the three flow body sizes are shown in in the table below. Low flow bodies often are machined out of a single piece of stainless steel bar stock. To get an idea of their relatively compact size, MFCs have the following approximate widths and lengths (not including inlet and outlet fittings): low flow—1.0 W x 3.0 L inches (25 W x 76 L mm); medium flow—1.5 W x 4.5 L inches (38 W x 114 L mm); and high flow—3.0 W x 9.0 L inches (76 W x 229 L  mm). MFMs usually have the same widths but have about two-thirds the length in the medium and high flow sizes.

Flow Body Size Maximum Mass Flow Rate Range (slpm)
Low Flow 0 to 50
Medium Flow 0 to 300
High Flow 0 to 1500

The flow body has inlet and outlet flow conduit fittings and houses the flow conditioning section, the flow sensor tube, the bypass/laminar flow element, and, in the case of MFCs, the control valve. The electronics are mounted in their enclosure on the top of the flow body. The wetted parts of a typical flow body and its internal components are made of corrosion resistant materials. Typical wetted materials for the flow bodies of general purpose MFMs and MFCs are: 316 L stainless steel; ferromagnetic stainless steel in the valve; and “O” rings and valve seats of fluoroelastomers and other advanced elastomeric materials. Some lower cost instruments intended for light duty and lower accuracy applications have flow bodies made of plastic or aluminum.

Instruments with elastomeric seals throughout the flow body have relatively low rates of leakage in and out of the flow body. MFMs and MFCs used in vacuum processes use metal seals at all locations in the flow body to further reduce leak rates. Manufacturers should subject every instrument to a helium leak check using a mass spectrometer leak detector, or equivalent instrument. Additionally, all instruments should comply with applicable pressurized equipment standards and codes, and manufacturers should pressure test all instruments to insure compliance.

Process lines typically are tubes with outside diameters of 1/8, 1/4, 3/8, 1/2, 3/4, and 1 inch (6, 10, 12, and 20 mm). The 1/4 inch (6 mm) tubing size is most common. Some MFMs operated at very high flow rates are available in wafer and flange pipe sizes. Manufacturers offer a broad selection of process tube fittings, including: compression fittings, elastomeric “O”-ring face seal fittings, and metal gasket face seal fittings. Since the inlet and outlet fittings contribute to the pressure drop in the instruments, the size of the fittings should be as large as practicable within constraints imposed by the size of the process line.

Semiconductor MFCs

Semiconductor MFCs often have a particulate filter, pressure regulator, and a positive shut-off valve installed upstream of the instrument and may have a positive shut-off valve and pressure regulator installed downstream. General purpose instruments also may include ancillary flow components in their installation.

Semiconductor MFCs used in the fabrication of high-end semiconductor devices have several special requirements to ensure that: (1) no particulates or other contaminants enter the fabrication process; (2) no toxic process gases escape the MFC; and (3) no ambient air enters the process. Typical specifications are: wetted surfaces must have high purity and be highly polished (surface roughness in the range of about 4 to 10 microinches Ra (0.1 to 0.25 micrometers Ra); leak rates must be extremely low; and internal flow paths, as shown in Fig. 3 (no figure 3 shown here), must have no sharp corners, cavities, or dead spaces where particles can form. Semiconductor MFCs are available in both in-line and down- port configurations. Down-port versions reduce the axial dimensions of the MFC and its ancillary flow components, thereby facilitating the compactness required by manufacturers of semiconductor equipment.

The Flow Conditioning Section of an MFM & MFC

The flow entering the MFM or MFC may have non-uniformities in its flow profile due to upstream disturbances caused by elbows, contractions, expansions, and the inlet fitting. This is particularly true for mass flow rates greater than about 50 slpm in the medium and high flow sizes. The flow conditioning section shown in the image above eliminates these upstream flow non-uniformities and conditions the flow so the sensor tube and bypass are able to create the necessary laminar flow in their passages. Downstream flow non-uniformities have no effect on instrument performance.

In operation, the jet issuing from the inlet fitting in enters the flow conditioning section and impacts a central plate. It then flows radially outward and strikes the cylindrical inner wall of a settling chamber. This tortuous flow pattern effectively erases any non-uniform past history of the flow.  A settling chamber then slows down the flow and allows viscous forces to reduce non-uniformities. The flow profile then becomes uniformed and flattened as the stream lines encounter a flow resistance as they pass through the inlet filter plate or screen that also captures any remaining particulate contaminants. After the inlet filter, the flow profile is further flattened as it passes through a flow nozzle. At this point, the uniformed flow splits into the two paths described earlier: one to the sensor tube and the other to the laminar flow element/bypass.

Low flow instruments with mass flow rates less than about 50 slpm, such as semiconductor MFCs, do not require a flow conditioning section. Because of this and the use of flow conditioners for higher flow rates, capillary tube thermal MFMs and MFCs of all sizes do not require straight lengths of upstream and downstream piping (i.e., tubing) that are required by most other kinds of flow meters.

To see how the flow conditioning section works, watch our video “How Capillary Thermal Mass Flow Controller Technology Works.”

Next up in the “Capillary Tube Thermal Mass Flow Meters & Controllers- User’s Guide” series, Dr. Olin describes the mechanical components of the sensor, bypass, and electronics.

Get more information on Capillary Tube Mass Flow Meters and Controllers:

Download Dr. Olin’s Complete White Paper “Capillary Tube Thermal Mass Flow Meters & Controllers- A User’s Guide.”

Read more about the History & Evolution of Mass Flow Controllers

Read Core Technology: Capillary & Immersible

Wireless Networks for the Digital Flow Meter, Part 1

Last time I wrote about unified communications, which is the ability to use discrete communications protocols within a protocol network. This time I want to expand on the physical aspects of the network as it relates to flowmeters, including mass air, oxygen, pipe, water and other types.

Let’s assume you’ve just purchased another five flow meters and go about “wiring” them into your infrastructure. You’ve enhanced your meters by utilizing a communications protocol for remote observation and control. You’ve hired a technician to install the meters within a pipe, located a source to power the meters and finally ran cable for the communication support. The communications line ends at your Remote Console that interacts with the meters.

So, in simple terms, your communications network looks like this:

You go to your Remote Console and examine and interact with a flow meter.  Now, what happens if you’re on the factory floor and need to examine data from your a flowmeter? The problem is that you’re not near your Remote Console.  Well, this problem has many names but is best known as the “last mile” problem. Simply put, in sending “data” (which can mean any type of data – TV/cable, voice, DSL, communications protocols, etc.) from the source to the destination, there are issues within the “last mile” or last part of deployment.

Case in point, when we moved into our house many years back, I decided to upgrade our DSL to the fastest that our area provided. After speaking with the sales person, they told me they had a complete fiber backbone that would provide the fastest fastest speed.  Excited, I decided to go for it and placed an order. The technician arrived, did the installation and informed me that I could not get the promised speed as the infrastructure in our neighborhood was not wired with fiber but standard copper. So, the phone company could get the fastest signal to our junction box in the neighborhood, but for the “last mile,” they were limited to whatever was historically there. It was just not cost effective to install new fiber to the whole neighborhood. Long story short, I could not get the fastest speed. I can only surmise that it was not cost effective for them to install new lines for a limited customer base (i.e., the neighborhood).

So, what do we do regarding your need for a Mobile Remote Console for your flow meter set-up? How do we create a communications “pipe” that does not require costly installation and maintenance? In one word: wireless. Let’s adjust your network layout to support wireless. In simple terms, it looks like this:

We insert a wireless device that will “pass” data from the communications pipe the flow meters are using to the laptop/console. Now, based on the range of the wireless signal, the user can walk around the factory floor with a Remote Console without any additional costs in infrastructure (i.e., no physical wire was installed) other than the wireless hardware. In our example, we avoided the “last mile” issue by using a wireless approach instead of installing wires for communications. What would happen if we changed the communications protocols in the future using wire? We may have to pull all the wire and install new wire. With the wireless solution, we may need to upgrade the wireless access points, but that’s it – no physical wires.

When you’re thinking about a wireless solution for flow meters, there are some factors to consider:

Security
How do you limit who can interact with the network?
Is the data encrypted?
What is the range and how far can the network reach from a single network router?
Can multiple routers be “daisy-chained” to extend the signal reach?

Interoperability
Does the router “play well” with other routers?
Does the router support standards-based protocols?

Up until now, I have talked about the Remote Console being wireless and the digital flow meters being wired.  In my next post, I want to further expand this discussion and talk about making meters wireless and what that means in the larger scheme of self-healing networks, mesh networking, remote observation and interaction.

Part 2: Wireless Flow Metering: More Than Just No Wires