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Teledyne Hastings Instruments Blog

Doug Baker

Recent Posts

See more clearly with the HVG-2020A Vacuum Gauge!

Posted by Doug Baker on Tue, Oct 09, 2018 @ 10:02 AM

HVG 2020A_76307_fingerWe at Teledyne Hastings Instruments are pleased to introduce the newest member of our vacuum measurement portfolio, the HVG-2020A.  The HVG-2020A is a piezoresistive vacuum sensor with an optional touchscreen display that reads from 0.1-1000 Torr.  The sensor uses 316 Stainless Steel as the wetted material and provides a gas independent pressure measurement, meaning your measurement will be accurate no matter what gas species is being used.  The HVG-2020A features an excellent accuracy rating of ±(0.1% of Reading + 0.5 Torr).  This rugged sensor comes in a number of system connections for ease of installation: 1/8” NPT, 1/4” VCR®, 1.33” Mini-CF, 2.75” CF, KF-16, KF-25, 1/2” Weld Stub, and 1/2” VCR. Let’s talk about some of the powerful features that allows the HVG-2020A to stand out.

5 Reasons Why You  Need the HVG-2020A

HVG 2020A_topAnalog I/O: The HVG-2020A has a 9 pin D-sub connector on top of the assembly that allows an analog output signal to be measured amongst other features.  The selected linear analog output signal is proportional to the full scale range of the sensor (1000 Torr). Available outputs are 0-1 VDC, 0-5 VDC, 0-10 VDC, 0-20 mA, and 4-20 mA.  The sensor will come configured from the factory with one of these outputs active, but can be easily changed by the user should output requirements change.  Through the touchscreen display, there is a menu that allows the user to cycle through the available output options.  If the HVG-2020A was configured without a touchscreen, the analog output can be changed via digital communications, which we’ll talk about in the next section.  In addition to the analog output, the 9 pin D-sub will have Hi & Lo set points.  The Hi set point is active when the pressure is above the set value and the Lo set point is active when the pressure is below the set value.  Finally, the 9 pin D-sub has a pin for input power.  The HVG-2020A can accept 12-36 VDC for power.  In the event, the user doesn’t have 12-36 VDC to send via the 9 pin D-sub, there’s a 24 VDC input connection port that’s compatible with a bayonet-style power supply.

 

Digitial I O for HVG 2020ADigital I/O:  As mentioned earlier, the HVG-2020A has a few different methods digital communication can be established.  First and easiest is the micro-USB port on top of the gauge.  This will allow the instrument to be directly connected to a computer without the need for adapters or extra wiring.  There is also a 4-conductor TRRS jack on top of the instrument.  This port can be used for daisy-chaining gauges together with RS485 or a standard RS232 communication connection.  Finally, the 9 pin D-sub will have two pins designated for TTL serial communication. These digital communications (with the exception of TTL) can be connected to a PC and used with our Free Windows software for the HVG-2020A.  The software has a number of features including data logging and customization/configuration of the gauge.  Digital communication also allows for command syntax to be sent manually to the instrument. These commands are especially important if the HVG-2020A was ordered without a touchscreen display.  Through digital communication, the user can issue commands that change the analog output, adjust set point values, stream pressure readings, or change pressure units, just to name a few.

 5 Reasons Why You  Need the HVG-2020A

Touchscreen Display:  The most powerful feature of the HVG-2020A is the touchscreen display.  The intuitive display allows for quick visualization of the current pressure without needing to have a separate power supply or remote display. There are five available views to choose from (shown left to right below): Pressure View, Pressure & Temperature View, Set Point View, Bar Graph View, and Pressure over Time View.  The pressure is always displayed on each of these five screens.

Various Digital Screens for HGV 2020A

There is also a menu button which will allow the user to cycle through a number of sub menus.  Through these menus the user can change the screen orientation should they mount the gauge in a position other than vertical, set the zero (this should only be performed if the system pressure is known to be well below 0.1 Torr), view device information such as serial number and firmware levels, change the analog output, cycle between RS232 or RS485 and a number of baud rates, and finally restore the configuration of the gauge back to the original factory setup.  The touchscreen display makes reading vacuum pressure as clear as 20/20 Vision!

 

LED Status Lights:  Lastly, the HVG-2020A features two LED lights on top of the instrument.  These are extremely helpful in getting a general idea of the current pressure and status of the vacuum gauge. The chart below explains each combination of Status & Vacuum LED.

Status and Vacuum LED Explanation

Simple Lab Set-up using Diaphragm Vacuum Pump

The HVG-2020A vacuum gauge is ideal for many applications requiring rough vacuum measurement.  The picture on the right shows a simple lab set-up using a diaphragm vacuum pump & an analog needle gauge.  The HVG-2020A would be a perfect fit for this set up.  With the local touchscreen display, extensive wiring and configuration is not needed.  Simply supply the gauge power and you are reading pressure. It’s easy to See why the “2020” is the vacuum gauge for the job! 

 

To learn more about the HVG-2020A or any of our other vacuum and flow products, contact us at hastings_instruments@teledyne.com, call 757-723-6531 (800-950-2468), or click the button below.

5 Reasons Why You  Need the HVG-2020A 

VCR® is a registered trademark of Swagelok Company.

Tags: vacuum gauges

Mass Flow Controller Calibration Report - What Does it Mean?

Posted by Doug Baker on Thu, Aug 23, 2018 @ 10:15 AM

In this short blog, we are going to look at one of our mass flow controller calibration reports and discuss some of the terms that you will see. There is good information at the bottom of these reports, so let’s jump in and take a closer look…

Sample Calibration Report

At the bottom of every one of our calibration data sheets, you will see the following statement:

This calibration complies with ANSI/NCSL Z540-1-1994 and ISO 17025-2005 [non-accredited] and is traceable to the National Institute of Standards and Technology. This validation was accomplished by qualified personnel directed by controlled procedures. The accuracy of this calibration for any gas other than the actual gas used may be subject to theoretical corrections. Customer Service can be contacted weekdays 8AM-5PM EDT at 1-800-950-2468.

Let’s start with part of the first sentence, “This calibration complies with ANSI/NCSL Z540-1-1994 and ISO 17025-2005 [non-accredited]”  According to the NCSLI webpage , there are two national standards for calibration laboratories. These are Z540-1 and ISO 17025. There are some differences between the two standards. And the aforementioned NCSLI gives a detailed description of both. In short, 17025 is appropriate for both calibration and testing labs whereas Z540-1 addresses calibration labs only. 17025 requires that the laboratory be a legal entity that can demonstrate competency, which includes thorough analysis of the uncertainty associated with the calibration services. Another difference between the two standards is that 17025 places the responsibility of the calibration due date on the end-user. In other words, the calibration lab should not determine the customers calibration cycle. That is why you no longer see calibration due dates on Teledyne Hastings’ labeling.

OK…. if 17025 is the latest, greatest, and accepted around the world, why do we still even list Z540-1 on our calibration reports? Because, we still have customers who adhere to Z540-1 and need the statement on their paperwork.

What about the word “non-accredited” that appears in parentheses? While we strive to conform to ISO 17025, which includes rigorous internal audit review, it has been our position that as a manufacturer, it is not necessary / appropriate for us to invest in the accreditation activities and third party audits. However, we do recognize the depth and critical nature of the standard.  Because of those criteria, we have chosen to compose our procedures and train our personnel to be in compliance with the standard. So to be clear, Teledyne Hastings is not accredited to ISO 17025.

Let’s move on… what do we mean by, “…traceable to the National Institute of Standards and Technology”? Simply this, we can provide an unbroken chain of calibration documents that connect your calibration back to NIST, the National Institute of Standards and Technology.

Vue_Touch_Screen-2

Now here is a trick question… does a NIST traceable calibration tell us anything about the uncertainty of the calibration? The answer is, “no”. For example, we could calibrate one of our most advanced mass flow controllers, the HFC-D-302B 300 Vue which has a stated uncertainty of ± (0.5% of Reading + 0.2% of Full Scale).

– or we could calibrate our HFC-202 flow controller (±1% of full scale using the same metrology and the stated uncertainty for each instrument would be the same as before. In other words, the performance of these instruments does not improve just because a NIST traceable standard was used.

One more note, some customers request “Backup Documentation” to their calibration data reports. In other words, they want copies of the calibration reports of our metrology that form the unbroken link from their calibration back to NIST.  There is a nominal administrative fee to collect, scan, compile, and email these calibration reports for each individual piece of metrology that was used.

stackes of paper

Does everybody need the Backup Documentation? Usually not, but enough customers request these so it is a service that we offer.  Quite often the reason why our first tier customer will request the additional supporting calibration reports is because they are manufacturing complex assemblies that their higher tier customers are procuring with the aforementioned unbroken chain back to NIST as a purchase order flow down requirement.

Next, we have the sentence, “This validation was accomplished by qualified personnel directed by controlled proceduresThis gives us an opportunity to tell a little about our ISO 9001:2015 Quality System. As a key part of our system, all assembly and calibration personnel must complete rigorous training and demonstrate proficiency before working on either the Flow Products or Vacuum Products Teams. Also, every product or subassembly acceptance test, that has a measurable output, is controlled by a top tier Quality System Procedure. The procedures, training program, in fact the entire Quality System is subject to routine internal audit program, third party surveillance audits, and third party ISO 9001:2015 certification audits.

ISO Certificate

Now what about the statement, “The accuracy of this calibration for any gas other than the actual gas used may be subject to theoretical corrections”?  There are certain gases which are hazardous and/or corrosive. While our flow meters and controllers are quite suitable for use in many of these gases, there are several of the gases that we have never (and will never) allow into our facility. So, we use theoretical corrections to map the output of our flow products using the calibration gas to the output for the user’s gas.

We are very proud of our metrology and quality programs. And we welcome your questions. If you have a question about mass flow controllers, vacuum gauges, or just want more information about a Calibration Report, we are here to help. You can contact us at hastings_instruments@teledyne.com  or call 757-723-6531 (800-950-2468).

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Tags: mass flow controller

What is a Vacuum Furnace, How Does it Function, And How is it Used?

Posted by Doug Baker on Thu, Jun 21, 2018 @ 09:58 AM

Teledyne Hastings is working to expand our throughput so that we can better serve our customers by meeting increased demand while decreasing lead times. Over the last several months, we have added and improved calibration systems in both our vacuum and flow production areas. We have also purchased a new vacuum furnace which increases our production capacity. In this blog, we will describe what a vacuum furnace is, how it functions, and how we use it.

A picture of our newest vacuum furnace is shown below.  The three major components of the vacuum furnace, from left to right, are the high-speed diffusion pump, the vacuum chamber with a high temperature hot zone, and the control cabinet. The diffusion pump is capable of pumping 180,000 lpm.  While the pumping speed may seem unnecessarily high for the given volume, keep in mind that the gas load, at high temperature, can be very high. The diffusion pump is connected to the hot zone chamber via a large right angle vacuum valve. The diffusion pump is backed by a rotary vane vacuum pump. Pressures in the foreline can be monitored by using a Teledyne DV-6R vacuum gauge tube. The base pressure of the system, with the heat zone at room temperature approaches 1 x 10-6 Torr.

Vacuum Furnace

 Leon Whitehead at the controls of the new vacuum furnace.

The hot zone is the heart of the vacuum furnace. A picture showing the inside of the hot zone is shown below. The effective hot zone size is 12”w x 12” h x 24” d. The molybdenum rod elements inside the hot zone are resistively heated once the system has reached sufficient vacuum. Under vacuum, the hot zone can reach temperatures exceeding 1300°C (2372°F).

Inside of Hot ZoneInside the hot zone. Note the series of Molybdenum rod elements.

 

The vacuum furnace is controlled by a touchscreen panel with PLC. The operator can select and execute a pre-programmed temperature/time profile for a given task. In addition, pressure and temperature at various locations on the system are monitored and displayed. The control cabinet also includes the transformers, contactors, and fuses. 

 

Teledyne uses our vacuum furnaces for both fusing and brazing operations - all while precisely controlling the environmental conditions within the hot zone. In a typical schedule, the system is pumped out to its base pressure and then the hot zone is brought up to 800°C. After reaching this temperature, the hot zone is held for a period of 20 minutes. Next, the hot zone is slowly ramped to 1100°C, which takes about an hour. The hot zone is then held there for up to 1 ½ hours.

Teledyne Hastings Instruments is an ISO 9001:2008 certified manufacturer and we produce a complete line of instruments for precise measurement and control of vacuum, pressure, and gas flow. Our vacuum furnaces and the corresponding Quality Work Instructions deliver consistent results, which in turn provide our customers with high quality instrumentation. For information on Teledyne Hastings and our Mass Flow Meters and Controllers or Vacuum Gauges, please visit www.teledyne-hi.com or click the button below.

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Tags: vacuum meters, vacuum gauges

Digital Flow Meters and Controllers now protected against dust and water - what that means for you!

Posted by Doug Baker on Thu, Mar 08, 2018 @ 08:39 AM

300 and IP-67.jpgTeledyne Hastings designs and build mass flow controllers for a broad array of markets from clean laboratory environments to heavy industrial installations. Recently, we have been asked to provide our newest line of Digital 300 Flow Meters and Controllers into more demanding environments. And, we are proud to offer an optional IP-67 enclosure, which provides protection against dust and water. More on our product later in the blog.

But first, let’s explore the IP, or Ingress Protection, rating system.  NEMA (National Electrical Manufacturers Association) publishes a standard (ANSI/IEC 60529-2004) entitled, “Degrees of Protection Provided by Enclosures (IP Code)”. The corresponding international standard is IEC 60529. The introduction to the IP Code starts:

 

This standard describes a system for classifying the degrees of protection provided by enclosures of electrical equipment for two conditions: 1) the protection of persons against access to hazardous parts and protection of equipment against the ingress of solid foreign objects and 2) the ingress of water.

 

The IP Code rates the degree of protection by using two numbers. The first number describes protection against solid particles; the second number describes protection against liquids. The Wikipedia page describing the IP Code provides a couple of nice tables to help us quickly understand the numbers.

Dust (First Number) Moisture (Second Number)

IP 0x - No Protection

IP 1x - Objects > 50mm

IP 2x - Objects > 12mm

IP 3x - Objects >2.5mm

IP 4x - Objects > 1mm

IP 5x - Dust Protected

IP 6x - Dust Tight

IP x0- No Protection

IP x1 - Vertically Dripping Water

IP x2 - 15 Degrees Tilt Dripping WAter

IP x3 - Sprayed Water

IP x4 - Splashed Water

IP x5 - Water Jets

IP x6 - Powerful Water Jets

IP 7x - Effects of Immersion

IP x8 - Indefinite Immersion

IP x9 - High Pressure, High Temperature Water Jetting

IP-67 in aquarium.jpgWhich now brings us back to the Teledyne IP-67 rated enclosure. The first number, “6”, indicates that our enclosure is completely protected against dust. The second number, “7”, indicates that our instrument can withstand submersion in water up to a meter in depth for up to 30 minutes.

One side note about IP ratings, if you follow the battle between Samsung Galaxy and Apple iPhone, you may have seen an article published by CNET last September (2017). In the article, it was stated that the iPhone 8 and 8 Plus are certified with an IP67 rating, while the Samsung Galaxy S8 is rated IP68. And by the way, yes… according to Reddit, the whole putting the wet iPhone in rice thing to dry it out, does work.  

In order to claim the IP-67 rating, Teledyne Hastings has sent test instruments to NCEE Labs in Lincoln Nebraska. In general, there are two tests, one for dust and one for water. Aaron Steggs, Senior Test Engineer with NCEE explains, “The testing to receive the dust rating is not trivial. There is a vacuum test on the enclosure to ensure that no ingress of dust can occur. The vacuum pressure used is 2kPa.”

Aaron goes on to explain a little about the water test, “When talking about immersion testing, there is a greater chance of water being forced into any opening due to the weight of the water about the instrument under test.”

In any case, we have passed both the dust and water test and now you can have the accuracy and fast response of the Digital 300 Series in an IP rated enclosure.

For more info about our digital 200 mass flow meters and controllers, please visit www.teledyne-hi.com or click the button below for more inforamation on the IP-67 version now available.

Interested in additional  information on the IP-67

 

Tags: mass flow instruments, IP-67

How monitoring instrumentation is helping preserve the Emancipation Proclamation

Posted by Doug Baker on Tue, Mar 06, 2018 @ 03:53 PM

Emancipation Proclamation Blog.jpgFebruary is the month when citizens in the United States celebrate the history and culture of African-Americans. In early Feburary, scientists from the Pressure & Vacuum Group at NIST (National Institute of Standards & Technology) installed a special case designed to hold President Abraham Lincoln’s first handwritten draft of the Emancipation Proclamation and 13th Amendment in the Smithsonian’s National Museum of African American History & Culture. You can watch a video of the installation here:

https://www.nist.gov/video/nist-behind-scenes-installation-emancipation-proclamation

 

The Emancipation Proclamation freed slaves in the Confederate States in 1863. After the Proclamation, the American Civil War becomes more about the struggle for freedom. In turn, Emancipation becomes law for the entire United States via the 13th Amendment to the US Constitution.

The priceless handwritten draft is now stored in in a sealed case with monitoring instrumentation. According to an article posted on the NIST website (https://www.nist.gov/news-events/news/2017/04/making-airtight-case-freedom ), the system tracks pressure, temperature, relative humidity, and oxygen content. The NIST article also says that the system uses 4% oxygen to help maintain the color of the iron gall ink.

Emancipation Oak Tree.pngNow, another interesting thing we can celebrate about the Emancipation Proclamation is the famous Emancipation Oak. Located on the campus of Hampton University, in Hampton Virginia. Note that Hampton is also the home of Teledyne Hastings. The Emancipation Oak was the site of the first reading of the Proclamation in the South according to the Hampton University Website (http://www.hamptonu.edu/about/emancipation_oak.cfm ). The tree has a diameter of over 100 feet and the oak has been designated as one of the 10 Great Trees of the World by the National Geographic Society.

For information on Teledyne Hastings and our Mass Flow Meters and Controllers or Vacuum Gauges, please visit www.teledyne-hi.com or click the button below

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Tags: General Interest

John Glenn, NASA Langley, and Hampton, VA

Posted by Doug Baker on Mon, Dec 12, 2016 @ 04:22 PM

As we say good-bye to John Glenn, it is a good time for Teledyne Hastings to recall with pride our company’s and our city’s connection to this great American hero. Now, many people know that John Glenn was the first American to orbit the earth. But most people don’t know that the original seven Mercury astronauts, including John Glenn, received their original spaceflight training in 1959 at NASA-Langley in Hampton Virginia which is also our home for Teledyne Hastings.

 

The Hampton Roads area of Virginia has memorialized several landmarks to commemorate Project Mercury. There are several bridges in the city of Hampton which are named for the astronauts. “Military Highway” was renamed to Mercury Boulevard. And, in Newport News, the Denbigh branch of the Newport News Public Library System is the “Grissom Library”.   

NASA was formed in late 1958 when NACA operations were converted over. Previously, NACA (National Advisory Committee for Aeronautics) was established in 1915 and built Langley field in Hampton. Now in doing some background reading for this blog, I found it interesting to learn that NACA was created out of fear that the U.S.A. might be falling behind the Europeans in aeronautics and that NASA, in turn, was created out of fear that the U.S.A. was falling behind the Soviets in the Space Race.

 

In a book entitled The Story of Hastings-Raydist, Carol Saunders points out that NACA did not hire many engineers during the first part of the Great Depression. But, in 1935, NACA accelerated hiring and they brought on Charles Hastings as a “Junior Scientific Aide”. In 1939, a newly hired mathematician named Mary Comstock was hired and placed in an office across the hall. The two were married and together created Hastings Instruments in 1944.

 

And speaking of mathematicians at Langley, there is a movie “Hidden Figures” (released December 25, 2016), which tells the story of three female mathematicians who were part of the computer pool. Which brings us back to John Glenn. In the early days of computers, engineers did not always trust the results of the electronic data processors. The computer pool, in other words, human mathematicians, were used to crunch through complex calculations. Before his historic flight in 1962, Glenn requested that one of these computer pool women, Katherine Johnson, verify the results of the computer. The contributions of these women to the space program was remarkable.

For more information on Teledyne Hastings Instruments click the button below or visit www.teledynehastings.com

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The following books were referenced in the writing of this blog:

Hidden Figures by Margot Lee Shetterly

Hampton - From the Sea to the Stars edited by James T. Stensvaag

The Story of Hastings-Raydist by Carol Hastings Saunders  

Tags: NASA

300 Vue - Inputs and Outputs

Posted by Doug Baker on Thu, Nov 17, 2016 @ 08:52 AM

Vue_Touch_Screen.jpgTeledyne Hastings is proud to release our newest, most advanced, line of digital flow meters and flow controllers - the 300 Vue. In this blog, we will discuss the three types of Input/Output (I/O) that can be used with the 300 Vue. These are: Analog, Digital, and Touchscreen Display.

 

(1)   Analog

The 300 Vue is very flexible. The instrument can be configured to give and receive analog signals. For example, the 300 Vue can use 0-5 VDC, 0-10 VDC, 4-20 mA, or 0-20 mA.

Let’s take a look at a 300 Vue flow controller which has been setup to have a full scale flow rate of 100 sccm and has 0-5 VDC I/O. In the case of a flow controller, there are two analog voltage signals that we need to understand. The first is the flow output signal. In our example (0-5 VDC), 5 VDC corresponds to 100% of the full scale of the flow controller. The relationship between the voltage output signal and flow rate is linear. So, if we have an output of 1 VDC from the 300 Vue, then we would have a flow rate of 20% of full scale which corresponds to 20 sccm (20% * 100 sccm = 20 sccm).

Correspondingly, in our example, the 300 Vue will accept an analog command signal between 0 and 5 VDC. Again, 5VDC corresponds to 100% command signal. The command signal tells the flow controller how to set the flow rate. So, if we wanted the flow rate to be 75 sccm, we would provide a 3.75 VDC command voltage  (75 sccm* (5 VDC/100 SCCM) = 3.75 VDC).

One last comment before we move on. Analog I/O is still used in many applications. Older flow power supplies and PLC’s often utilize analog I/O. The 300 Vue flow instrument makes it easy to integrate into these systems.

Interested in more information on the Vue? click here

(2)      Digital

The 300 Vue can provide digital I/O via RS232 or RS485. Connection to the digital port is made via the micro USB connector or the small bayonet-style connector. Let’s take a quick look at an RS232 command for the 300 Vue. If we send “F”, the 300 Vue will respond with the flow rate.

f <cr> <lf>

25.889 sccm

 

Simple - right? Now in the case of a flow controller, we will want to be able to send a command signal to tell the flow controller how to set the flow rate. One way to do this is to use V5, the “Setpoint”. The Setpoint Command is simply the flow rate expressed as a percent of the flow controller’s full scale. So, “V5=100” will set the flow rate to 100% of full scale. You can also use V4 which sends the command in the given units, as opposed to % of full scale.

Digital communication with the 300 Vue can be utilized in a few different ways. First, you can use our free user software which can be obtained from our website. If you want to see all of the capability (including flow data logging) you can watch this short “How To” video.

Next, many of our digital flow controller users write their own code using LabView. By working with the “F” and the “V5=  “, or “V4=  “ commands, the user can easily read and control the flow rate in their application.

Here at Teledyne, we often use TeraTerm for communicating with our digital flow instruments. Click to visit TeraTerm website for more information.   

TeraTerm is nice because it is open source (free) yet it is very powerful. I also like the fact that TeraTerm allows the user to save and restore a communication set up file. In other words, once you have a TeraTerm “ini” file working, you can save it so that you don’t have to reconfigure the settings each time you start up the program. If you have TeraTerm and would like a copy of my setup file for the 300 Vue, just send me an email

Interested in more information on the Vue? click here

(3)      Touchscreen Display

Ok, we’ve talked a little bit about analog I/O and digital communications. Now, let’s explore the coolest feature of the 300 Vue – the color touchscreen display. With the touchscreen display, it is very easy to see and control the flow rate. First, we should point out that the 300 Vue flow instrument is very easy to power up; you just plug in the connector and you are in control.

Top View with Plug.jpg 

Once the flow instrument is powered, the flow rate is observed as shown in the picture below:

DSC_0155m.jpg 

Now, to change the flow setpoint or command signal we touch Setpoint and we see the numeric keypad screen as shown below.

DSC_0161m.jpg 

Changing the setpoint is easy… you just type the value you want and hit ENTER. The display then returns to showing the flow rate.

 

The 300 Vue is very flexible with respect to Inputs and Outputs. If you have questions about I/O, our applications engineers are always standing by and ready to help. You can reach us at hastings_instruments@teledyne.com or by calling 1-800-950-2468.

Interested in more information  on the 300 Vue Series

Tags: Digital Flow Meter, Flow Controller, 300 Vue

Fundamentals Vacuum and Mass Flow Technology

Posted by Doug Baker on Wed, Jun 22, 2016 @ 10:27 AM

One of the goals of these blog postings is to give readers knowledge about vacuum and mass flow technology. The Society of Vacuum Coaters has established a foundation (SVCF) with a similar goal. Dr. Don McClure (Acuity Consulting & Training) has created “The Vacuum Wizard Video”. Dr. McClure worked at both IBM & 3M and has been teaching for over 20 years about vacuum coating onto flexible substrates.

Generic_Roll_Coater_Designs.jpg

As stated on the SVCF website, “The Vacuum Wizard Video brings to life the fundamentals of vacuum and vacuum coating technology through an informal and thought provoking presentation using non-technical jargon and filled with live demonstrations.

The Vacuum Wizard Video seeks to raise awareness of students and educators about the fascinating world of vacuum and vacuum coating technology. The only prerequisite is a curiosity about this amazing technology.

The Vacuum Wizard Video can be a useful training tool in the corporate world for personnel who require a basic understanding of vacuum technology. Sales representatives, customer service personnel, field service and maintenance technicians, lab technicians, and engineers with no vacuum technology background, can all benefit from the Vacuum Wizard Video.”

Vacuum_Model_2002_Gauge.jpg

(Check out the Teledyne Hastings’ Vacuum Model 2002 Vacuum Gauge on the table)  Click the button below to request an evaluation sample of the 2002 Vacuum Gauge

 Request   Evaluation Sample

You can get more information about the SVC Foundation and the video series by visiting:

http://svcfoundation.org

Click to see a sample of the Vacuum Wizard Video 

 

Tags: vacuum gauges, Mass Flow

Desired Characteristics of a Thermal Mass Flow Sensor - Part 2 of 2

Posted by Doug Baker on Tue, Jun 09, 2015 @ 11:58 AM

This is part two of a two-part blog on Thermal Mass Flow sensors.  In part one, we described the desired characteristics of a thermal mass flow sensor.  In part two, we will discuss the operation of the 300 series flow sensor (Patent #6,125,695) and how its design addresses the desired traits.

300_series_flow_sensor_insideIn our previous blog, we showed a cutaway of a thermal mass flow meter.  Now let’s take an inside look at the 300 series flow sensor:

When gas is flowing through the bypass shunt, a small pressure drop is developed which will direct a fraction of the flow through the arced / semi-circular capillary tubing in the flow sensor. On the outside of the capillary tube, there are two resistive wire coils which are tightly wound and in excellent thermal contact with the tube. These two identical windings are referred to as:

  • Upstream Heater Coil (1)
  • Downstream Heater Coil (2)

Associated with each of the two heated coils is an ambient coil. The ambient coil is in excellent thermal contact with the aluminum ambient block.  Aluminum has a very high thermal conductivity which ensures that both ends of the sensor tube and the two ambient coils (3 and 4) will be at the same temperature.

heated_coils_upstream_downstreamTwo identical Wheatstone resistance bridges are formed from the two pair of coils (see image on right).

The circuit shown in the image on the right is designed to ensure that the heated coils (upstream and downstream) are maintained at a constant temperature (ΔT) above the corresponding ambient coils.

Next, we calculate the power (W) required to maintain ΔT by:

Power_Formula

This power will be calculated for both the upstream bridge and the downstream bridge. It can be shown that:

 Upstream_downstream_bridge_formula

So, by maintaining both heaters at the same ΔT above ambient, the mass flow rate is directly proportioned to the difference in power (W) between the two bridges. For example, when no flow is passing through the capillary sensor tube, the power needed to maintain ΔT will be the same (i.e. ṁ = 0)

As gas flow increases in the tube, heat is transferred from the upstream heater to the gas stream.  This will force the upstream circuit to use more power to maintain ΔT. In turn, the gas will transfer heat to the downstream heater which will cause the downstream circuit to use less power to maintain ΔT.

LinearityNow, here is the best part: the mass flow rate is directly proportional to the power difference. In other words, LINEARITY!

In our previous blog, we discussed how excellent linearity leads to improved accuracy. And, not only does the 300 series sensor give excellent linearity, the circuit shown on the right reacts very fast to changing flow. Thus, the 300 series has excellent responsive time.

One last note, we have designed the 300 series to use relatively large diameter tubing.  This larger tubing allows flow meters to be designed with lower pressure drop than many mass flow meters on the market.  

Visit our website for more information on Teledyne Hastings 300 series Flow Meters.

Teledyne Hastings' Thermal Mass Flow Sensors are used worldwide.  Download our application note on High Throughput Leak Detection to learn about improving lead testing precision and throughput and how to reduce testing time.  

High Throughput Leak Detection

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Tags: Flow Meter

FAQ Corner - Units for Vacuum Measurement

Posted by Doug Baker on Mon, Sep 22, 2014 @ 04:23 PM

Earlier this year, the applications engineers here at Teledyne Hastings discussed topics for our blog. We all agreed that one of the more frequent questions that we discuss with folks involve the units used to measure vacuum levels. We find the technicians who use their vacuum systems daily often seem to develop a sixth sense about the “health” of their systems. They know something isn’t quite right when the base pressure (or rate of pressure change) is not what they expect. So when pressure measurements are not consistent from batch to batch, that is the time when the user stops to ask the meaning behind the data that their vacuum measurement instrumentation is providing.

Now, most users know that vacuum is commonly measured using units of pressure. There are a few different sets of pressure units and this blog will discuss the more commonly used ones. In Armand Berman’s book, Total Pressure Measurements in Vacuum Technology, pressure unit systems are divided into two categories: “Coherent Systems” and “Other Systems”.

Coherent Systems of Units are based on the definition of pressure (P) as the force (F) exerted on a chamber wall per unit area (A). P = F/A.  The International System of Units, or SI units, is commonly used for pressure measurement. http://physics.nist.gov/cuu/Units/units.html  The SI unit for pressure is the Pascal (Pa). It interesting to note that at NIST (National Institute of Standards and Technology), published papers are always required to use the SI set of units. Again, the SI unit for pressure (force per unit area) is the Pascal. 1 Pa = 1 N /m2.

Now, the Pascal as a unit of pressure is not always the most convenient because vacuum systems are often operating in a range of pressures where we would need to collect data using large numbers. For example, near atmospheric pressure, we would measure approximately 100,000 Pa. So a more convenient unit, the bar, has been derived. (1 bar = 100,000 Pa)

Moving lower in pressure, it is very helpful to then use the mbar (1 mbar = 0.001 bar). So many vacuum users, especially in Europe, use the mbar as the basis for describing pressure levels. As a specific example, look at the base pressure specification of a turbo pump, it will be given in terms of mbar (e.g. Base Pressure < 1 x 10-10 mbar).

Another system of pressure units is based on the Torricelli experiment (shown in the diagram). In this experiment, the pressure exerted on the mercury can be shown to be P = hdg, where h is the height of the mercury column, d is the density, and g is the acceleration due to gravity.

 

Simple Barometer
 

 

By measuring the mercury column height, the user can determine the pressure. The Torr unit (named for the Italian scientist Torricelli) has been defined to be 1 millimeter of mercury (1 Torr = 1 mmHg). This unit is very common, especially in the United States. It is also common to use the mTorr (1 mTorr = 0.001 Torr). Many years ago, pressure was sometimes described in terms of “microns”, which simply meant a mercury column height of one micron (1x10-6 m). Note that the micron and the mTorr are the same.

One last word about the units used to measure vacuum: on occasion, there is confusion between pressure units. As we have seen above, the mbar and the mTorr are not the same. One mbar has the same order of magnitude as one Torr  (1 mbar ≈ 0.75 Torr).  The table below gives some approximate conversion values. A useful website for conversions:

 http://www.onlineconversion.com/pressure.htm

 

 

Pa

mbar

Torr

mTorr (micron)

Atm

1 Pa =

1

0.01

0.0075

7.50

~ 10-5

1 mbar =

100

1

0.75

750.06

~ 10-3

1 Torr =

133.3

1.333

1

1000.0

~ 10-3

1 mTorr (micron) =

0.1333

0.00133

0.001

1

~ 10-6

1 Atm =

101,325

1013.25

760

760,000

1

 

 

 

 

 

 

Douglas Baker is the Director of Sales & Business Development of Teledyne Hastings. Antonio Araiza prepared the Torricelli experiment drawing. Antonio is the head of Technical Documentation at Teledyne Hastings (and is among the best soccer referees in the Commonwealth of Virginia).

Tags: Teledyne Hastings Instruments, pressure, mTorr, mBar, micron, pascal, torr, vacuum pressure, units of measurement, vacuum gauges, vacuum meters, vacuum controllers