Brooks Instrument Blog

Thermal mass flow controllers are traditionally calibrated for a specific gas, a desired flow range, and a set of operating conditions. Over time, the use of conversion factors based on a ratio of specific heats between gases came into use as a way for users to configure a single mass flow controller for multiple gases. This method of configuring a mass flow controller for multiple gases is still common today – you’re using it if your device lets you select a gas by: rotating a knob, pressing a button on a display, or sending an RS232 command to the device.

Accuracy is the primary issue with this method of conversion. Converting flow rates between the calibration gas and another gas based on a ratio of specific heats can result in a mass flow control error of 5-6%. This error is the result of the conversion method because it ignores other property differences that exist between gases in the real world. If you’re changing the gas on your device with one of the actions above, ask the manufacturer of your mass flow controller what the accuracy of the device is for a gas other than the calibration gas.

P.S. If you’re told that such a device is linear in all the available gases and thus the mass flow accuracy doesn’t change when the gas is changed, RUN! This is not physically possible. Feel free to contact us for comparison data.

Multiflo by Brooks Instrument is a leap forward in configuring a mass flow controller for multiple gases because it converts based on gas differences in specific heats, densities, and viscosities. Multiflo-Capable mass flow controllers cut the conversion flow control error in half compared to devices that convert gases based on a specific heat ratio alone.

This video demonstrates how a Multiflo configuration is performed on a mass flow controller. We welcome your thoughts or questions in the comments below.

You can find more information on Multiflo-Capable mass flow controllers on the Brooks Instrument LinkedIn company page. Your local Brooks product expert would also be happy to help you configure a Multiflo-Capable mass flow controller for your applications using the information entered on this form.

If you’d like to read a bit more about instrumentation and process control, feel free to check out more of my contributions summarized on my Google Plus profile.

While we were cleaning out our offices a few weeks ago a co-worker of mine handed me a great Norman Rockwell oil painting that we used to have hanging in one of our hallways. It was taken down when we were updating our facility. He wasn’t sure what to do with it. The reason we used to have it hanging up in the walls at Brooks (and the reason I’m going to find it another nice home on our walls) is because in the background of the picture you can see some Brooks Sho-Rate variable area flow meters between the two men on the left. Brooks provided Sho-Rate flow meters to  NASA for some of the first missions into space. Read more…

It’s official! Brooks Instrument has launched its online store. Now we can give customers quick and easy access to the Brooks family of products. Best of all, we’re offering free shipping on all orders within the domestic United States.

Currently, the store offers the 2500 Series plastic tube flow meters (rotameters) for purchase. In the coming months, we’ll be adding pressure gauges, pressure transducers, mass flow controllers, mass flow meters and more.

Our goal is to get Brooks’ products into the hands of customers as efficiently as possible to support your application needs. So, stop by the online store and check back to see what’s new in the coming months!

The first attempts to replace the horse as the primary mode of transportation involved burning wood to create steam to drive a steam engine. If the new crop of biotechnology and renewable energy companies realize their dreams we will once again be fueling our transportation and even using chemicals created from wood cellulose and other plants. Genetic engineering which has been the catalyst in the revolution of drug and food development is now being used to tackle our need for renewable fuels. I had experience, while still a student in the late 1970s, on the potential of enzymes to breakdown cellulose into sugar the basic building block for chemicals. I even had dreams of creating a cellulose driven economy but with oil costing only $20/bbl, I soon realized it would be difficult to compete. The catalyst driving the current group of bio energy hopefuls is the need to find renewable fuels which are better for the environment. Three conversion technologies are actively being funded. Read more…

In my last post I talked about UL Listed versus Recognized.  This time we are going to take a look at the IP and NEMA ratings and what they mean.  With this information you should be able to decide what minimum level of protection you need for your application.

Let’s start with the basics.  What does IP and NEMA stand for?  IP stands for ingress protection and NEMA stands for National Electrical Manufacturers Association.  Both IP and NEMA are rating systems for equipment that might be exposed to liquids, rain, ice, corrosion and contaminates such as dust.

An IP number contains two numbers (i.e. IP65) in most instances which relate to the level of protection provided by an enclosure or housing.  The first number relates to protection from solids as follows: Read more…

Thermal mass flow controllers and thermal mass flow meters are used to measure and control the flows of gases. The measuring terminology usually includes words like “standard” or “normal” flow. A standard cubic foot of gas is the same as an actual cubic foot of gas only if the measurements are taken at some standard set of conditions (STP); like 70 degrees F and one atmosphere ambient pressure. If the ambient conditions change, you may never know how much gas you have in a volumetric measuring chamber, but, if you use a device that measures standard cubic feet of gas, you will always know the flow.

Thermal mass flow controllers and meters use a sensor that measures standard units. If you are measuring 30 psi nitrogen at 100 degrees F, the device will indicate the amount of standard cubic feet per minute (SCFM) flowing or it could indicate in standard liters per minute (SLPM). Either way, you can change the actual temperature and the actual pressure and the measuring device will still indicate flow in standard units.

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83% of all instruments used in the chemical process industries (CPI) are being talked to using analog communications. By analog communications, we mean 4-20 milliAmp mainly. But we see 3-15 psi air and 0-5 volt control systems also. Why wouldn’t you use some of those 1’s and 0’s?

Actually, we have no idea just what percent of devices are being operated in the analog mode. 83% just seems like a good guess; although some at Brooks Instrument suggest it is much higher.

When you survey the field devices in your plant, you will find 5 major classes of instruments; flow, temperature, level, pressure, and analyzers (DO, pH, Cl2, etc…).

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I’m very excited to introduce you to the official Brooks Instrument Blog! This blog will be a great place for processing audiences from all industries to learn more about Brooks products, technologies, interesting applications, industry trends and so much more. Plus, the blog is a great place for you to share your ideas and opinions about all types of flow, pressure and level products and applications.

We plan on updating the blog more than once a week in categories such as Coriolis and thermal mass flow, level measurement, pressure applications, direct liquid injection vaporizer solutions and variable area meters. We’ve put together a great core team of experts that will post to the blog, including members of Brooks’ management, sales and product management teams. I encourage you to post comments on any or all of the blog entries as it’s a great way to share knowledge and find suggestions from some of the industry’s leading specialists.

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