EtherCAT in vacuum and industrial applications

EtherCAT in vacuum and industrial applications

Posted by: Michael Diaz

Manufacturers of Vacuum Deposition systems are increasingly turning to software-based industrial PLCs. These PLCs offer a variety of benefits, including greater productivity, precision performance, cost savings, speed-to-market and the ability to add processes like motion control and machine vision in the future.

Because there are so many different Ethernet fieldbus standards available, it’s difficult to choose one. Adopting the wrong standard can mean unnecessary cost and sacrificing competitive advantage due to slower performance.

MC-ethercat-vacuum-logoFor the control and regulation of vacuum coating processes, data speed and integrity are crucial. EtherCAT has been designed especially for these kinds of applications and meets all demands for fast controls. EtherCAT is a high-performance, low-cost, easy to use Industrial Ethernet technology with a flexible topology. The EtherCAT Technology Group promotes EtherCAT and is responsible for its continued development. EtherCAT is also an open technology, so anyone is allowed to implement it.

EtherCAT is the fastest Industrial Ethernet technology, but it also synchronizes with nanosecond accuracy. This is a huge benefit in applications where the process is controlled via the bus system. The rapid reaction times work to reduce transition times between process steps. In this way, EtherCAT’s performance leads to improved efficiency, greater throughput and lowered costs.

EtherCAT delivers the features of Industrial Ethernet at a price similar to that of a traditional fieldbus system. The only hardware required by the master device is an Ethernet port, eliminating the need for expensive interface cards or co-processors. EtherCAT slave controllers are available from various manufacturers in several formats.

EtherCAT P is a new addition to the EtherCAT protocol standard. It enables not only the transmission of communication data, but also the peripheral voltage via a single, standard four-wire Ethernet cable. EtherCAT and EtherCAT P are identical in terms of the protocol technology, only the Physical Layer differs. By providing the power supply via the communication cable, EtherCAT P offers additional cost benefits and enhances numerous applications.

Alicat now offers EtherCAT compliant Mass Flow and Vacuum Controllers. We have taken the extremely fast response time of the Alicats and paired it with the speed of EtherCAT. The EtherCAT technology has been seamlessly integrated into the product family, along with other Profibus, Modbus and DeviceNet.

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

Precision & Repeatability in Fiber Optic Manufacturing

Precision & Repeatability in Fiber Optic Manufacturing

Posted by: Ryan Barner

In the optical fiber industry, manufacturers’ needs center around precision and repeatability. It’s somewhat analogous to archery, where accuracy means hitting the bullseye. If you can hit the same point on the target every time, that’s precision. Repeatability is being able to demonstrate the same precision every time you walk up to the line and shoot. Let’s take a look at how optical fibers are manufactured, and where Alicat fits into the picture.

How Optical Fibers Are Manufactured

The fiber optic manufacturing process begins with the creation of a preform, where layers of very pure glass are built up on a rod. Different types of gases in very specific amounts are used to deposit a new glass layer on each pass, and every layer that is laid down on the base will give the end fiber a different property. A flame uses fuel gases, operated by a mass flow controller, to maintain a certain temperature and ensure the process is running optimally. The layering process sometimes takes place over the course of many hours depending on the size of the preform.

After the preform is created, it is then placed into a drawing tower. As one end of the preform is heated, inert gases are used to keep the heating element from burning up during the process. As the first drop falls from the melted end, a thin fiber is produced and then cools in a cooling tube filled with nitrogen as it descends through the tower.

The thickness is measured, quality is checked, and depending on the end use of the product, a coating process may apply a very thin polymeric or acrylic layer on the outside of the glass. This coating helps to protect the pure glass from environmental conditions and preserve the important properties within the glass fiber itself. Pressure control regulates the flow of this liquid polymer. In an extrusion-like process, it coats the fiber. Flow pressure needs extremely precise and repeatable control to provide a consistent coating over the product. Even a tiny amount of pressure fluctuation could lead to microns of variation in the overall thickness, which could dramatically affect the overall performance of the fiber. During the UV or Thermal curing, the material is keep in a an inert atmosphere to help the curing process. These gases are again controlled by mass flow controllers.

Depending on the size of the preform, it’s possible to run a fiber that spans anywhere from thousands of feet to hundreds of miles. We’re talking about pulling something to the width of a human hair and spooling it at 90 feet per second for hundreds of miles, while still maintaining uniformity. This is why the initial phase of making the preform is so important—to make a uniform product, the mass flow controllers must offer precise, repeatable controls of the gases that are used to deposit the different layers of glass.

Alicat’s Role in Fiber Optic Manufacturing

Fiber optic companies use Alicat products in several different aspects of the preform process and drawing process. During creation of the preform, we can be used for the burner control application, which controls the fuel gases which heat up the preform and help to control the deposition of each thin layer. We can also control the actual gases being used to create the very pure glass being deposited. And our mass flow controllers are used in the drawing process, where argon is being fed into the furnace area to keep the element from burning up. (The end result depends on the shape of the cone.)

About every five milliseconds, signals from our measurement sensors go through our entire processor. Depending on the type of process and operating pressures, the controller will have a control response of 50 milliseconds or less. (Sometimes we can help to tune that number down to sub-50 millisecond timeframes.) For anyone who might have a hard time imagining how fast this is, it takes the average human 300 to 400 milliseconds (thousandths of a second) to blink their eyes. Before you can even blink, our instruments have already obtained hundreds of measurements. To put that into perspective, in one second the gas burners and flow in the cooling tower may be adjusted over 200 times. That’s how we’re able to maintain repeatability and accuracy while a fiber is produced at 90 feet per second.

More Data Collection Means More Insight into the Process

Specialty fibers for high energy applications need to have very specific optical properties, which are shaped by the density and mix of materials. Therefore, depending on the part of the process, engineers want the ability to see as many parameters as possible. With an Alicat, you not only get the mass flow measurement, but also absolute pressure, volumetric flow, and temperature information so that you can refer back to it later. From a quality control perspective, you can use these parameters to determine what changed in the process and correlate that to a run that was rejected because of a defect.

Typically, the signals that provide this information go into some sort of a controller (a PLC) for interpretation. In case of a spike or a zero flow condition, the Alicat controller would send a signal to the PLC, which would then be able to shut down the line. Instead of having hundreds of feet or even miles of unusable product, it gives manufacturers the opportunity to identify that there’s a problem, get it fixed, and start the process again quickly.

Podcast of the interview for this post:

Compensating for Changing Environmental Conditions

Local environmental conditions can drastically affect the optical fiber manufacturing process. Unfortunately, we still find manufacturers that are used to the old way of doing things, where they don’t have the ability to adjust to changes in environmental conditions. For example, a particular manufacturer is located in an area that experiences heavy thunderstorms, which cause changes in barometric (atmospheric) pressure, and that causes an inconsistent product. With a storm in the neighborhood, they might decide not to even begin their 12-hour process, depending on the day’s forecast. Alicat can overcome and compensate for those changing atmospheric conditions and allow the manufacturer to produce high quality fiber—regardless of weather—because we measure flow in the context of pressure changes.

Other glass shaping processes

Mass flow instrumentation is used in many other glass processes besides fiber optics. Container manufacturers use mass flow controllers for regulating the gas flow to their melt process. There are also manufacturers that use mass flow to control the flame used to make fiberglass for structural components. Architectural glass is another huge consumer of mass flow controllers. They have an oven that’s hundreds of feet long, which requires precise temperature control to create a consistent glass product. (These are typically huge sheets of plate glass.) At any given zone of the oven, a specific temperature must be maintained with very precise flow control of fuel. Alicat mass flow controllers are deployed by architectural glass manufacturers to coat the glass to create different properties in the final product.

In the days before industrial automation was available, someone who gained years of expertise could determine the correct temperature just by looking at the color of the flame. They eventually learned how to make slight manual adjustments while walking down the line. What will the company do when those people retire? That’s where digital mass flow controllers come in—automation allows people to focus on developing optimal process conditions and monitoring parameters within the furnaces. Once everything is set up, it’s possible to know exactly what flow rates are needed to maintain the proper temperatures. The process is repeatable, and it provides useful data that can help identify why there may have been an inconsistency in the glass. The end result is greater repeatability, efficiency and a much better product.

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

About that Pressure Control Loop feature? It’s so cool

About that Pressure Control Loop feature? It’s so cool

Posted by: Alyssa Jenkins

As an applications engineer at Alicat Scientific, I talk to people in every industry all over the world and learn about how they use our product. One of the most interesting applications I’ve seen is in a chemical reactor, where our mass flow controllers are used to control pressure and make sure that processes are repeatable.

Our flow controllers can be set to control on pressure while measuring mass flow. Our mass flow controllers measure volumetric flow rate, mass flow rate, temperature, and pressure. (It’s possible to control on any of those except temperature.) By controlling on pressure, you essentially have a pressure controller and mass flow meter in a single device. It’s a fairly unique option, and it takes a second to appreciate how valuable it can be.

Most other mass flow controllers don’t provide much flexibility, allowing only for control of mass flow. Take, for example, the pressure decay method to perform a leak check—you’ll use a pressure controller to set the pressure, stop the flow, and wait for pressure to decrease. Then you can perform calculations based on the exact volume and gas used. (This requires you to have extensive knowledge beforehand.) If you have a pressure controller with mass flow measurement, you’ll see the leak rate instantaneously—as soon as the pressure settles. This saves you time, calculations, and physical space, too.

Here’s a 47 second video to help you visualize it:

What is Closed Loop Pressure?

Closed loop pressure is our term for using a feedback loop based on pressure instead of mass flow. A mass flow controller will typically measure the mass flow and adjust the valve open or closed to increase/decrease the mass flow to the desired level. When controlling on pressure, the valve will adjust based on the pressure measurement. For example, let’s say you’re controlling pressure downstream of the Alicat and want to reach 100 psi. If you’re currently at 80 psi, the mass flow controller will open the valve further until the pressure reaches your set point. This is useful whenever you have an application where you want to control pressure and determine the flow rate. It could be leak checking, flow checking, or quality checking where you have a specific flow vs. pressure curve that needs to be met. Here, your end goal would be to keep variation within certain tolerances to make sure that the product meets your quality standards.

Hear Applications Engineer Alyssa Jenkins talk about the Pressure Control Loop feature in depth:

MCD With CLP and Totalizer

MCD closed volumeOur mass flow controller with dual valves, closed loop pressure, and totalizer is a bidirectional controller with three ports (inlet, process, outlet) and two valves: one with incoming flow and another separate exhaust valve. It can control a closed volume of pressure, meaning not only can one valve open or close to increase/decrease the flow rate, but it can also exhaust to atmosphere or vacuum pump if you overshoot the pressure. The totalizer measures the amount of flow that has occurred. There are four different ways to determine the total amount of flow using these bidirectional meters:

  1. Add positive flow and subtract negative, allowing the total flow to go negative
  2. Add positive flow and subtract negative, not allowing the total flow to go negative
  3. Add positive flow and ignore negative flow
  4. Add positive flow and subtract negative flow, resetting when it reaches 0

You’ll know how much is in that specific volume at any given time, which is important if you want to measure the amount of gases going into a system.

Using Alicat With Rotameters

A rotameter has a floating indicator in a graduated tube.

A rotameter has a floating indicator in a graduated tube.

Rotameters measure volumetric flow rate, and they are tuned at a very specific pressure to give the mass flow rate. While they may be marked in standard liters per minute (slpm) or standard cubic centimeters per minute (sccm), this reading is only valid at the pressure for which the rotameter was tuned. An Alicat, on the other hand, is valid at all times because it has a pressure sensor that adjusts the reading when the pressure changes. Comparing rotameters to Alicats is like comparing apples to oranges because they are measuring different things, unless the rotameter is at it’s very specific calibrated pressure. However, since we can control pressure with an Alicat mass flow device, why not control to the pressure to which the rotameter is tuned?

We’re typically talking about the setting the pressure downstream of the rotameter, so it’s simply a matter of placing the Alicat downstream with the valve on the opposite side, so that you are controlling the back pressure from the valve, through the Alicat and the rotameter. Then you can measure the flow directly on the mass flow meter and the rotameter at the same time. Of course, you must make sure that the Alicat has the rotameter’s gas and standard conditions selected. They aren’t adjustable on the rotameter, but they are adjustable on the Alicat. You can choose from hundreds of gases (up to 130, but most standard series have 98 selectable options) along with user-selectable standard temperature and pressure.

Why Choose Alicat?

Solving unique problems is probably my favorite part of being an applications engineer. When it comes to Alicat products, everything can be customized to suit a customer’s needs. If a customer has a unique application that we haven’t seen before, the solution might involve making some small tweaks, like putting a valve in a different place or adding a relative humidity sensor. For instance, right now we’re figuring out how to work with 500 liters per minute of sulfur dioxide. Because it’s highly corrosive, we need to use 316 stainless steel and FFKM. One of my colleagues is also working on making our new IP or NEMA rated instruments more durable. We started a whole redesign of the system based on the input of a couple of customers.

If you have an application that you think might require a customized solution, call Alicat to speak with an applications engineer. We’ll answer your technical questions to the best of our ability and help you figure out if there is a custom solution we can build to meet your needs.

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

Customizing mass flow and pressure controllers: brilliant to baroque

Customizing mass flow and pressure controllers: brilliant to baroque

Posted by: Dan Yount

Many customers, even our most loyal ones, don’t realize that we customize just about EVERY Alicat instrument order. That’s because all our instruments are built when you order, and configured and programmed to best suit the application and conditions for which you’re buying them. Customizations can range from having a meter automatically tare itself every 24 hours, to engineering new limits of what our pressure controllers can handle! To give you an idea of how we work out your new requests, here are some simple and helpful customizations we produced on request.

Local Valve Drive Percentage

Resulting from a customization created at a customer’s request, the Local Valve Drive (LVD) option lets you monitor the work your valve is doing—because it can help you assess whether your process is in trouble. The LVD parameter appears on the large, multivariate display screen of an Alicat mass flow controller (or pressure controller), right above the main parameter output in the center. The LVD option reports the proportion of power being applied to the valve to maintain the setpoint. Valve drive percentage is something our devices normally track internally, and is a useful data point in troubleshooting, should you ever need it (our free lifetime support, available by phone or email, can help you with any troubleshooting you need). The value to the customer is that it serves as an indicator of the overall health of their chemical reactor vessel’s inputs and outputs. A significant change in the valve drive may indicate several possible failure conditions. Here’s a quick video showing this simple and smart customization at work:

Our “Local Valve Drive” (LVD) customization allows you to see how much drive is being given to a valve from your controller. One of our customers wanted a quick way to diagnose if their reactor’s output was dropping. Given steady pressures and flow rates, the valve drive will consistently be within a certain range. Our customer knew that at 30 PSIG inlet pressure with 10 SLPM of flow, the valve driver would be somewhere between 35-40% full power typically. If they saw the valve drive creeping much higher than this, then they would know that they were losing pressure differential in the process, since the valve was needing to open the valve wider than usual to create the same amount of flow. It may be that something is clogging the valve, making it open wider to allow flow to pass through. If they saw the valve drive percentage at 100 this would indicate that the valve was 100% open, or it was at least trying to be that way. They’d know that their reactors were creating such little output that it wasn’t possible to generate enough flow to satisfy their setpoint.

Local Valve Drive is now an option you can ask for, if your application calls for it.

Controlling pressurization speed

A customer wanted to use a pressure controller to maintain a certain pressure within a leak test chamber. However, they also wanted to make sure that the chamber would not pressurize too quickly.

MCD-Series bidirectional mass flow controller, shown with IPC option

MCD-Series bidirectional mass flow controller, shown with IPC option

To assure this, we built them a dual-valve mass flow controller in our MCD Series. A dual-valve mass flow controller can be programmed to fill with one valve and vent with a second valve. Like all our standard MFCs, it can be set to control flow based on pressure, rather than mass flow, (while still measuring mass flow!) Our dual-valve mass flow controller is also able to measure mass flowed in either direction. The MCD series of mass flow controller can be perfect for dispensing gases into a closed volume without overshooting or overpressurizing, or as an instantaneous pressurized leak test, with a built-in pressure relief valve for quickly changing the devices under test.

The customer used pressure control mode so that the setpoint was in pressure units, not mass flow units.

Finally, we created a custom software feature: a “Mass Flow Limit” function, configurable through the front screen. This would operate as a governor on the flow rate. It tells the valve to not open any further, once a certain mass flow rate was reached. This effectively limited how quickly the unit was allowed to pressurize their system.

Custom Configuring: a Stainless, IP-rated Dual Valve Pressure Controller

Customization can come in the form of unique combinations of options. Like this PCDS–it’s a dual valve pressure controller with a lot of options added on:

psds-ip65-remotevalve_lr

  • Stainless flow bodies and corrosion-resistant seals for using aggressive gases
  • A remote pressure sensor port (it’s on the backside of the flow body with the display), so that the pressure control will be based on a remote volume, independent of the valve lines.
  • IP-65, a liquid ingress prevention rating, means all the connectors are sealed with gaskets, and the display panel doesn’t have our menu buttons
  • The second valve is remote. The cable is the right length to mount the “relief” valve in a different location of the process flow.
  • Modbus industrial protocol on board. Without interface buttons to program the device, remote commands are necessary. But the display will provide a visual confirmation of the operation of the device for any technicians on the scene.

Altogether, it’s a very unusual device.

What’s your application?

When you place an order, our apps engineers always ask a lot of questions, like “What is the application? What are the operational parameters, and what are you trying to do?” This guides them in recommending things like custom tuning of valves (no extra charge!), or the selection of a particular sensor, or communications options. We do our best to make the device perform at its very best in your hands. Sometimes that means custom engineering, sometimes just custom configuring of existing options. Alicat prides ourselves in our ability to accommodate many custom configurations, or invent a solution!

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

How can I take advantage of PID Tuning?

How can I take advantage of PID Tuning?

Posted by: Jas Gill

Alicat flow and pressure controllers use closed loop control algorithms to achieve their highest degree of control stability. The algorithms are a mathematical relationship that dictates the response of the valve to the flow or pressure conditions. It assesses the difference between the set point and the process value—whether it be mass flow, volumetric flow, or pressure—as an error. The degree of error determines what kind of input to send to the valve, reaching the correct value in the quickest time possible. The amount of time expended to minimize the error—and therefore the control response of the controller—depends on what type of loop is being used (PD or PD2I) and what P, D and I values are used.

When you order your controller, we set the Proportional and Derivative values by trying to replicate the application parameters (process conditions) to the best of our ability before we ship it to you. This customization to your system is one reason our controllers are fast.

No worries

If process conditions change, the valve response may change drastically depending on how much you deviate from the conditions the valve was tuned at. You need not worry about erratic response from your controller if the conditions change, since PID tuning can be done in field to get better control at the new process conditions. You can change PID terms through the display panel buttons, or through electronic commands using digital or analog communications.

You’ll get optimal performance from your controller when you select correct values for all three parameters (two in case of single valve controllers). The ‘P’ term opens the valve to achieve the set point, ‘D’ term applies a damping influence to eliminate the overshoot and ‘I’ function helps the system settle to the set point.

A previous blog describes the P, D, I terms:
Achieving Responsive and Stable Valve Control with PID Tuning
Briefly:

  1. Proportional (P): The P term applies power to the valve as it tries to decrease the error between the set point and the process value position to achieve the set point.
  2. Derivative (D): Think of this as a damping term which tries to reduce the rate of change. The larger the D term, higher the damping influence on the valve drive.
  3. Integral (I): Integral in calculus is the area under the curve, it determines the output of the valve as a function of the sum of all the errors. I term takes into account previous readings to reduce the error and correct the process value to the set point.

 

Oscillating around the set point

If your controller shows signs of oscillations about the set point, or is unstable in its control response, it is a sign that the P term is too large. The greater the P value, the greater the range of oscillation. To get rid of the oscillation (settle the controller to set point), you would need to decrease the P term.

Let’s say you have a 10 SLPM controller set to 10 SLPM for Hydrogen. The controller is oscillating between 8 and 12 SLPM. Hydrogen is a low viscosity and a very light gas compared to Air. This being the case, the valve—which is tuned with air—should be re-tuned. So, starting with the factory P value (for example, it may be 1000), try decrements of 10% and keep on going down until you see the controller settle to the set point quickest. Generally, we only touch the D terms after you have altered the P term, so if you still have small oscillations, you can increase the D value with 5-10% increment. This should help the controller become more stable.

PID response shown graphically, by varying P

Excessive P (purple) produces oscillation. Low P (red) slowly rises to the setpoint. Optimal (green) settles quickly.

Delayed setpoint

A second situation is when your controller takes too long to get to the set point or never achieves the set point, but settles to a flow rate or pressure below the set point value. This implies either too small a P value being used or too large a damping influence. Using the analogy of a car, imagine you want to get to 70 miles per hour. but when you start increasing the speed, someone applies brakes which decreases the acceleration of the car. The car may never get to 70 mph if the deceleration is larger than acceleration, and the car may settle at a speed of 60 mph when acceleration = deceleration, or the opposite forces are equal.

In this case, try increasing your P value in 10-15% increments until you see the controller getting close to your set point. Next step would be to decrease the D value to help the controller get to the set point in a quicker time. If you start seeing some oscillations, that means the D value has been set too low.

Control loop adjustment is all about getting a good feel of how the controller responds to changes in the P and D terms. The gas viscosity, inlet pressure, back pressure can greatly influence how the valve responds. Tuning the valve is an art rather than science and the more familiar you get with your controller, the better you’ll be able to tune it.

 

 

 

 

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

Alicat Mass Flow Controllers Powers MDC’s XpressStick Gas Delivery Module

Alicat Mass Flow Controllers Powers MDC’s XpressStick Gas Delivery Module

Posted by: Edgar Schrock

Gas connection module benefits from Alicat’s MCE’s high precision flow control

Alicat Scientific’s MCE mass flow controllers have been integrated into MDC Vacuum Products’ XpressStick™ MFC Gas Stick. With precision control of gas flows of up to 20SLPM and onboard display, Alicat’s MCE provides gas programming functionality to the gas connection module, which links pressurized gas inputs to vacuum chambers.

The Alicat MCE accurately controls gas flow rates as low as 0-0.5 sccm full scale or as high as 0-20 slpm full scale. With 20 to 50 millisecond control response times to setpoint changes, the MCE improves vacuum coating end products and helps eliminate target poisoning.

The MCE mass flow controller helps drive precise doses of gases for mixing and purging in vacuum coating systems

The all-in-one design of the XpressStick MFC gas stick eliminates complex hardware specification in processes which include a combination of specialty gases, pressure, precise regulation, and vacuum. Its easy programming and precise gas control system allows users to go from bottle to process in one simple step. Designed to meet ultra-high purity process requirements, the XpressStick is also offered in a stainless steel model for corrosive environments.

With the MCE’s zero warm up time, the XpressStick is ready to control process flows in just one second, with real time mass flow, volumetric flow, absolute pressure and temperature data, fully compensated for temperature and pressure. The gas module is programmed directly through the MCE’s integrated display, with easy changes to gas type using the on-board gas calibrations.

“Fast response time, accuracy, and reliability were all key criteria in choosing an MFC instrument for our XpressStick,” explained MDC Vice President of Engineering & Technology, James Moore. “Based on past experience with Alicat, we knew that they could deliver all three, with an integrated display that enables our all-in-one design.”

Alicat mass flow controllers, pressure controllers and vacuum controllers are used in vacuum coating systems around the world.

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

Totalizer Averaging Smooths Out the Data in Flow Measurements

Posted by: Alyssa Jenkins

Alicat’s optional totalizer feature is a great way to meter the total flow through a system. Adding a totalizer to a controller means you can dispense fluids in set quantities. We call it batch mode: set a total mass desired, set a flow rate, and the controller stops when the delivery amount is reached.

Totalizer averaging adds another number to your totalizer screen—the average flow rate during the metered period.  Calculating the average after the sample has finished is simple, but real time averaging can be tedious and require additional programming.  Why not just have it on the screen?  Not only does totalizer averaging appear in the screen, it also appears in the serial data stream—right next to the totalizer value. Now you can easily streamline your existing communication programs.

tot-avg-screen_highlighted_800

Totalizer averaging can be extremely helpful during leak checking or flow characterization.  Using a mass flow device to control the pressure on a device under test and while measuring the flow rate is a compact solution essentially including two devices in one.  For smaller flow rates and volumes, minute changes in pressure will force changes in flow rates—which in turn change the pressure.  This can lead to an oscillation of both pressure and flow rate.  While the oscillation is natural, it can make it difficult to determine a single number to report.  With totalizer averaging, the average flow rate can easily be seen and recorded in real time rather than waiting until the process is complete to calculate.

Alicat devices have always had a flow averaging feature available to help minimize noise, since we sample in milliseconds. For users who are unaccustomed to a fast-responding sensor, the totalizer averaging can be easier to read, and helps to correlate our flow measurements to results from slower-responding instruments.  Totalizer averaging gives the ability to average flow measurement data over variable periods—from milliseconds to hours—extending the possibilities.

If the totalizer software is already on your device, the totalizer averaging feature can be added easily in the field via serial communication.  For those who are familiar with serial communication, simply add 1024 to the current number in register 88.  (Need a little help getting set up for serial communication?  Our applications engineers can help you out). The totalizer option itself is described on the product options page.

Here’s a video that shows how easy it is to use the Totalizer Options:

The totalizer option and totalizer averaging can be added to most Alicat mass flow and liquid devices ordered since 2003. Contact our applications engineers for more information about how to upgrade your unit today—get your serial numbers handy.

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

Gas Chromatography’s mobile phase and mass flow control

Posted by: Joe Ancona

It’s safe to say that a Gas Chromatograph is one of the most important tools one will see in an analytical chemistry laboratory. Chromatographs are the workhorses of the analytical trade. When it comes to separating, analyzing, verifying purity, or determining concentrations of various chemical concoctions, the “GC” as it is commonly known, can provide a quick, accurate, and repeatable result for a large cross-section of known compounds. Of course, to have precision in analyzing means all the components in the system must work as expected. A clean ‘column,’ appropriate for the substances being separated, a properly prepared sample, diligent injection methodology, and a stable mass flow rate of the inert carrier gas are all required.

Basically, a modern gas chromatograph is designed to take a sample in the form of a ‘slug’ and pass it through a long ‘column’, as carried by a steady flow of inert gas. While the sample moves through the column in a computer-controlled oven, it’s heated to various temperatures, and its output is fed to the detector array. The sample and carrier gas are eventually vented out as waste.

The key measurement function of the GC is centered on timing. As the components of the sample are separated in the column, they emerge at different times and in rising and then falling intensities. The detector simply plots the peaks against time (retention Rt) and strength (peak area). Based on known chemistry, the components and concentrations of the original sample can be determined with amazing accuracy.

Misnomers and misconceptions

If you’re unfamiliar with how a gas chromatograph works, let’s dispel a couple of misnomers and incongruities. First, there is no traditional vertical ‘column’ inside the GC! (The decades old classic ‘column chromatography’ process does in fact use an actual glass tube, up to several feet tall. The column effects the purification of individual chemicals through a powder or slurry, using the principals of partition equilibrium.) Although the over-arching concepts are very similar, the modern GC’s column is now a very thin, coiled capillary tube. These fine quartz or fused silica tubes have only 0.1 to 0.53 millimeter internal diameters, but are cut to 12 to 100 meters in overall length! Modern capillary tube columns are internally coated with a thermally stable, high molecular weight polymer. This extremely thin polymer layer (0.1 – 10 thousandths of a millimeter) is referred to as the ‘Stationary Phase’.

A second common misconception comes from the word “Chromatography” itself. When you see ‘Chroma’ you might think ‘color’. When you see ‘-graphy’ you would normally assume there is some type of written or printed result. Just as the ‘column’ sub-component name has carried over from traditional separation techniques, so has the ‘chroma’ element. In the early days of thin layer chromatography (circa 1900), it was the actual colors of the various compounds in plant materials spread across the paper stationary phase which gave the Chromatography process its name.

Lastly, there isn’t a universal gas chromatograph for every compound. Some aspects of the sample to be tested must be known in advance, so that the right kind of GC is used. Different chemical groups need different columns, tailored to their properties. Certain volatile compounds need to be vaporized, and kept that way, meaning oven heating schedules must be selected for the best separation resolution. Most importantly, there are many different types of detector heads to match the appropriate selectivity of the test sample. Detector technologies include flame ionization, thermal conductivity, electron capture, photo-ionization, conductive, and so on… A majority of the detection technologies are dependent on steady state mass flow rates.

Timing is everything

As the various chemical compounds move through the capillary via the flow of inert gas—called the Mobile Phase—each will effectively ‘stick’ to the walls of the column at varying levels of adhesion and therefore will elute through the tube and into the detector head at different times. This happens regardless of the steady flow rate of the carrier gas, since the compounds all have a unique—and therefore identifiable—affinity to the stationary phase coating inside the capillary. All of the compounds make it through eventually; but it’s how fast they make it through that distinguishes one from another. Because of this, it is imperative for the carrier gas flow rate to be constant; otherwise flow rate would become a seriously disruptive variable to the detection of a particular chemical compound.

Imagine a sturdy wooden ramp in your backyard, used to roll different types of balls across a freshly cut patch of grass. Starting at the top of the ramp, a bowling ball rolls down, and across the yard. It’s barely slowed by the friction of the grass. A Bocce ball has a similar result, but doesn’t quite make it as far as the bowling ball. A soccer ball falls someplace in between the two. A whiffle ball hardly goes a few feet past the end of the ramp, and a ping pong ball is stopped within inches. Obviously, each ball has its own mass, diameter, angular momentum, rolling resistance, etc., but within reason, one could determine which ball is which, just by how far it rolled on the grass; once the norms were established. This assumes of course that the uniform grass surface (think: polymer coating in column) isn’t swapped out for a rocky dirt lot (a contaminated column), and that the fixed wooden ramp (a.k.a. the steady carrier gas flow rate) isn’t raised or lowered randomly during testing (unstable gas flow).

Minimizing the Variability of Flow

The effectiveness of a gas chromatograph relies heavily on stability and repeatability. Whether it be the method of injection of the sample, the computer controlled oven temperature profile, the use of a clean ‘blank’ (just ask any DUI lawyer about that one!), or the steady state flow of the carrier gas, the only variable in the process should be the sample itself.

Alicat Scientific, Inc. specializes in both precision mass flow control and high speed/high accuracy pressure control; each of which can be used to deliver exacting inert gas flows to your GC column. Even in low flow regimes, our mass flow controllers can provide stable flow from zero to full scale within tens of milliseconds. Each MFC has the ability to measure and control up to 98 default (common) gases and gas blends; changeable on-screen, or via digital control. No matter what inert carrier is being used for a particular test (N2, He, Ar, CO2), you can use the same Alicat MFC for each, so long as it is set to the gas being flowed.

If the GC uses a fixed orifice that requires stable pressure control, Alicat produces a wide range of electronic pressure controllers (both standard and OEM electronic pressure regulators) which can be custom tailored to just about any flow rate/pressure condition/speed, achieving the best result possible.

For verifying flows in a particular gas chromatography system, or to calibrate the gas delivery components within a GC, use one of our portable calibration flow meters to quickly establish proper carrier gas operation:

Our flow measurement technology has been used and trusted for over 25 years by some of the leading gas chromatograph manufacturers in the world.

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

7v Firmware Update Makes Interface More Intuitive for Alicat Flow and Pressure Instruments

Posted by: Danielle Adams

We’ve just made it easier to use your Alicat mass flow meters and pressure controllers from their front panels. This post has all the details on our 7v firmware update, which features a more intuitive user interface.

If you’ve been with Alicat for very long, you’ve seen us add new menu selections to our flow and pressure instruments from time to time. We incorporated these features into a set of “Miscellaneous” menus (MISC1 and MISC2) in order to preserve the existing interface. However, after filling up MISC1 and MISC2 with new functions, we decided it was time to give the entire menu system an intuitive update.

Alicat mass flow controller showing new basic configuration menu

Alicat mass flow controller showing new basic configuration menu

Here to explain the motive behind these changes is Brian Clandenon, Alicat’s Senior Software Engineer:

“As Alicat has added more functionality to our instruments, the idea was to make minimal changes to existing buttons in the menus. While this was reasonable for each small change, so many changes built up over the past few years that some related functions became scattered across multiple menus. This made the menus more challenging to navigate and to remember.

Alicat mass flow controller showing new advanced setup menu

Alicat mass flow controller showing new advanced setup menu

One goal of a good menu system is to make settings easy to find, so it became time to review the overall structure of the menus. We endeavored to organize the settings in ways that would be more intuitive to new and existing users alike, so that the changes would outweigh the inconvenience of learning the new locations.”

The following FAQ describes the changes to Alicat’s menu structure in the new 7v firmware.

Which instruments are affected by this change?

All Alicat-branded instruments manufactured on or after May 22, 2017, will ship with 7v firmware, with the exception of no-change customers who have not yet approved this update.

Can I update my existing instruments to 7v?

Alicat’s 7v firmware update is compatible with most Alicat instruments that have serial numbers of 135,000 or higher. Some instruments with serial numbers between 80,000 and 135,000 may also be compatible with 7v. Upon request, we can update your firmware to 7v during your instrument’s next annual recalibration at no charge. Alternatively, we can update instruments outside of the recalibration process for a firmware update bench fee of $80 (USD).

Will my new 7v Alicat communicate the same as my existing 6v Alicats?

Yes. Communications protocols and commands have not changed in the move from 6v to 7v, so your command set will remain the same, no matter which protocol you have been using.

Which changes will I notice?

Alicat mass flow controller showing new main menu

Alicat mass flow controller showing new main menu

The new menu map is reproduced on the following page. Below, you will find a listing of changes to the menu structure. Please see your new operating manual for more details.

  • A new BASIC CONFIG menu allows easy access to GAS SELECT, DEVICE UNITS and STP/NTP options. The GAS menu option also displays the currently selected gas.
  • A new TARES menu gives you access to flow and pressure tares, plus AUTO TARE.
  • A new ABOUT menu collects DEVICE INFO, DEVICE STATE and MFG INFO in one place.
  • The contents of the old MISC, MISC1 and MISC2 menus can now be accessed via the ADV SETUP menu, with the exception of STP/NTP, which is now in BASIC CONFIG.
Feature New Menu Location (7v Firmware) Old Menu Location (6v, 5v or 4v)
AUTO TARE MENU > TARES MENU > CONTROL SETUP
CONTROL SETUP MENU > CONTROL MENU > CONTROL SETUP
DEVICE UNITS MENU > BASIC CONFIG MENU > MISC
DIAG TEST MENU > ABOUT > DEVICE STATE MENU > MISC > MISC2 > DIAG TEST
FLOW AVG MENU > ADV SETUP > SENSOR SETUP MENU > MISC > MISC1
GAS SELECT MENU > BASIC CONFIG > GAS MENU > GAS SELECT
LCD CONTRAST MENU > ADV SETUP > DISP SETUP MENU > MISC > MISC1
MFG DATA MENU > ABOUT > MFG INFO MENU > MFG DATA
MODEL INFO MENU > ABOUT > DEVICE INFO MENU > MFG DATA > MODEL INFO
PRESS AVG MENU > ADV SETUP > SENSOR SETUP MENU > MISC > MISC1
ROTATE DISP MENU > ADV SETUP > DISP SETUP MENU > MISC > MISC2
RS232 COMM MENU > ADV SETUP > COMM SETUP MENU > RS232 COMM
STP/NTP MENU > BASIC CONFIG MENU > MISC > MISC2
TARE P w/BARO MENU > TARES > TARE PRESS MENU > MISC > MISC2 > TARE P w/BARO
ZERO BAND MENU > ADV SETUP > SENSOR SETUP MENU > MISC > MISC1

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com

The RS-232 Communication Protocol and your Alicat instrument

Posted by: Joe Ancona

The 55-year-old RS-232 protocol is the default method of talking to Alicat devices. Aside from RS-232, you could configure your instrument with RS-485, Profibus DPV1, ModBus RTU, DeviceNet, and Ethernet IP protocols. For the bulk of our customers however, the tried and true RS-232C communication standard will remain the go-to method for commanding and reading Alicat devices.

The Not-So-Standard RS-232 Standard

One of the main reasons that RS-232 has survived for over five decades is that it is a useful, but low level and rudimentary signal, with fairly loose operational guidelines. In 1962, the sole application for the RS-232 communication standard was connecting electromechanical typewriters and their host mainframes/modems, commonly known as ‘Teletype’ systems.

When more advanced electronic machines were developed subsequently, proprietary adaptations led to nonstandard pin assignments, connectors and signal voltage levels. For example the original specification called for a DB-25 connector, but in the last 30 years most RS-232 products have adopted a DB-9 connector (technically called DE-9M).

The ‘data’ being sent on RS232 lines are simply positive (+) and negative (-) voltage pulses relative to a ground reference. A group of +/- pulses sent by one device are carefully timed by the receiving device and decoded into whatever the hardware settings deem to be data bit packages. In other words, the RS-232 standard only defines a relatively loose general electrical framework to transmit and receive electrical pulses. What one does with all these pulses is ultimately up to the connected hardware. Things like character encoding, spacing, start bits, stop bits, bit order, error detection, bit transmission rate, etc. are not the responsibility of the RS-232 scope, and are established by the user’s connected circuitry, usually in the form of a serial communication port and its associated chips and transistors.

db9-pins

It’s the COM Port’s job to make sense of the pulses on behalf of the attached computer or peripheral. For reference, an RS-232 system must transmit from one device (sent on its Tx pin), to a receiving device (received on its Rx pin), and vice-versa. Do not try to connect Tx to Tx or Rx to Rx in an RS-232 three wire system! The only pin that is connected directly is the ground pin, which gives both ends a common reference point to measure the pulses from. Each RS-232 driver uses inversion logic and employs a single ended, bi-polar output voltage to feed to a UART (Universal Asynchronous Receiver/Transmitter). Because the system has three wires and two distinct channels of communication, it is considered a “Full Duplex” system. Data can be transmitted at the same time as it is being received.

RS-232, the Alicat Way

Understanding how loose the RS232 “standard” really is, you might be wondering how Alicat uses it. Alicat does offer the ubiquitous DB-9 or the “standard” DB-25 connector, but we can provide RS232 communication on any connector that is offered, such as DB-15, 6 pin industrial locking connectors, and of course the default 8 pin miniDIN jack.

Alicat RS-232 Specifications

However, our real departure from the standard, is how Alicat has exploited signal levels and allowed for multiple units to work on the same COM Port. Because Alicat devices neither accept nor produce negative voltages, a traditional +/- 15V RS232 is not possible. Fortunately, a positive only pulse of +5V can be made to replicate an RS232 waveform (logic high ‘mark vs. logic low ‘space’), readable by 99% of all UARTs used today.

Once UART serial ports went out of fashion in the early 2000’s, USB to serial converters took their place; most today use the FTDI chipset to replicate the COM Port. Alicat’s unique signal profile is also fully compatible with these devices.

In addition to bending the rules for signal level and polarity, Alicat has also designed a clever work-around for being able to use up to 26 units at once on a single serial COM Port. The technical term for this capability is called ‘Multi-Drop’ communication, and is supported by all Alicat units equipped with serial communication (whether RS-232, or the differential signal based RS-485). Through multi-drop communication, every device on the line is configured to have a unique identifying letter (A-Z), and every unit listens to the commands that have been sent. However, even though each device ‘listens’ to each command, a particular unit will only accept and respond to the command if the instruction begins with that instrument’s unique ID letter.

So you can read the current flow rate on unit “A”, give a new setpoint to the MFC “B”, and reset the totalizer on unit “C”; all while being hooked together on the same three wires (electrically in parallel).

Even though the RS-232 communication ‘standard’ itself is old enough for a place at the Smithsonian Institution, it is still heavily used today for all types of computer based systems that talk to various peripheral components. Employing the universal ASCII (American Standard Code for Information Interchange) character set as our language, Alicat instruments will continue to be sold with the robust, universal, and reliable RS-232 system for the foreseeable future. For basic connection and terminal examples please see our video and instructional here:

Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: sales@sensorguys.com Website: www.sensorguys.com