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Teledyne Hastings Instruments Blog

Vacuum Gauge Series: Thermocouple Gauge Tubes

Posted by Devin Seran on Mon, Apr 12, 2021 @ 04:02 PM

Vacuum Gauge Series - Thermocouple Gauge Tubes Fun FactTeledyne Hastings was founded in 1944 as The Hastings Instrument Company by Charles and Mary Hastings. The late 1940s saw the introduction of thermal sensing technology at the young company which became the foundation for many early Hastings instruments such as air velocity indicators, thermal mass flow meters, stack emission monitors and, of course, the thermopile vacuum sensor.

By 1964, Hastings Instruments had grown into one of the leading vacuum and thermal mass flow instrument companies in America. Today, our popular Thermocouple Vacuum Gauge Tube product lines, including the DV-4, DV-5, and DV-6, are trusted around the world where repeatable, rugged, and dependable vacuum measurement is needed. Based in Hampton Virginia for over 75 years, the highly skilled employees at Teledyne Hastings are dedicated to delivering the highest quality thermocouple vacuum gauge tubes.

How does a thermocouple gauge tube work?

How a thermocouple vacuum sensor works is simple! As an example, let’s take a look at the DV-6R, shown in the diagram to the right, along with the representative schematic.

There are three thermocouples shown (A, B, and C) in the diagram. Now, an individual thermocouple consists of two dissimilar metals which are joined together at a junction. At the junction, there will be a small voltage which is a function of temperature. During operation of the gauge tube, thermocouples A and B are resistively heated inside the gauge tube’s housing. Now, since the wires connected to A and B thermocouples are exposed to the gas in the vacuum, thermal energy will be transferred away from the wires at a rate which is dependent on the number of collisions between the gas and the wires and thereby depends on the pressure inside the tube.

Vacuum Gauge Tube Illustration DV-6R-resized-183

Let’s consider two extremes. In high vacuum, where the pressure is very low, there will be fewer gas collisions with the wires and the tube’s voltage output will be relatively high. (Higher temperature corresponds to higher thermocouple output). Now, towards high pressures, more gas results in more thermal energy being carried away from the wires and the thermocouples run at a lower temperature and so give a relatively low output.

 

How to use a thermocouple vacuum gauge tube:

To use a thermocouple vacuum gauge tube, you must connect the gauge tube with an instrument that correctly excite the tube’s wires and also converts the output of the gauge tube to the correct pressure measurement. Note that new gauge tubes from Teledyne Hastings are manufactured to the highest quality and are tested to be very repeatable from tube to tube.

So let’s take, as an example, the use of a DV-6R vacuum gauge tube with a DCVT-6 panel meter or HPM-4/5/6 handheld meter. Both the DCVT-6 and HPM-4/5/6, out of the box, are setup to provide the correct activation to the DV-6R. The output from the gauge tube is then monitored by the instrument and the correct vacuum level is displayed for the user.

In the case of the DCVT, two contact relays are available to the user for process control. The user can simply dial up the desired setpoints and the dual relays will independently toggle when the vacuum setpoint has been crossed. You can now easily understand how Teledyne repeatable gauge tubes will lead to repeatable process control! The DCVT also provides serial communication (RS232) and linearized analog output options (0-1 VDC, 0-5 VDC, 0-10 VDC, 4-20 mA).

Teledyne Hastings' Vacuum Products
DCVT-6 HPM 4/5/6 DV-6R DV-6S
Model DCVT-6 Vacuum Gauge

HPM

DV-6R-resized-183 DV-6S-1

Application Example:

Gas Plant Tanks 182395563There are many applications where a thermocouple vacuum gauge tube is an excellent choice. One example we will briefly discuss in this short blog is vacuum insulation or vacuum jacketing. The technique of using a vacuum guard or barrier to thermally insulate a cryogenic or refrigerant tank is straightforward: remove the air from around an object and eliminate conductive heat transfer. The better the vacuum is then the better the vacuum insulation. To effectively measure pressure in the mTorr range, a vacuum dial gauge is simply not sensitive enough.

A vacuum reading can be obtained from any of the DV-6 tubes using either a dedicated electronic display or handheld battery-operated readout. The Hastings’ DCVT provides continuous monitoring with an easy to read LED display. For periodic vacuum checking of one or more tubes, the hand-held HPM 4/5/6 is recommended. For convenience, it is powered by a 9V battery and can be connected to any DV-6 tube for an instant reading. To ensure the most accurate measurement, the DB-20 Reference Tube (with NIST Traceable calibration) can be used to validate the electronic calibration.

If you would like to learn more about vacuum jacketing click here.

For more information about any of our thermocouple sensor series or vacuum gauges, we are here to help. In addition to LiveChat on our website, you can contact us at hastings_instruments@teledyne.com or call 757-723-6531 (800-950-2468) or click the button below.

Contact Us

Tags: vacuum gauges, Thermocouple Gauge Tubes

Women's History Month - Celebrating Mary Hastings

Posted by Doug Baker on Mon, Mar 08, 2021 @ 10:00 AM

Mary HastingsMarch is Women’s History Month and this year we’d like to focus on Mary Hastings, one of the key founders of Hastings Instruments. Mary Comstock graduated from William & Mary with a degree in physics with minors in math and chemistry. She was truly a pioneer in many ways. After college, she took a job as a “computer” at NACA (National Advisory Committee for Aeronautics) in Hampton, Virginia. There, Mary met Charles Hastings, a young engineer who had his office across the hall from her. The two were married in 1940.

In a business era that was almost thoroughly dominated by men, Mary was an invaluable contributor to the success of Hastings Instruments. She promoted the fledgling company through press releases that she prepared for local papers and thereby helped to secure critical financial support. She attended shareholder meetings of other companies to learn how they conducted their annual meetings. For many years, Mary prepared the annual report for Hastings shareholders. In short, she was not afraid to tackle any challenge that would help grow the company. Moreover, Mary was a constant voice of wisdom to her husband with respect to company decisions and policy. She accomplished all of these things while the couple raised three children.

It is reasonable to assume that without Mary Hastings, the company would not have been nearly as successful. So during Women’s History Month, we want to celebrate her many accomplishments. You can hear more about Mary from her daughter Carol Hastings Sanders in this video:

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

Carol Hastings

 

Tags: Teledyne Hastings Instruments

Freeze Drying of Flowers - Happy Valentine's Day!

Posted by Doug Baker on Fri, Feb 12, 2021 @ 08:57 AM

freeze dried flowers courtsey of Flowers ForeverHappy Valentine’s Day 2021! Time for me to run out and order some freeze-dried flowers for my wife. What?... yes, it’s true! In case you have not heard of this, freeze-dried flowers can make a beautiful gift.

 

According to Flowers Forever – Bellabeads of Columbia SC, https://myflowersforeverjewelry.com/pages/freeze-dried-flowers, freeze-dried flowers will, “retain their beauty as if frozen in time as a lasting memento.” They can be placed in shadow boxes or frames and stored for many years.

So this is probably the best time to tell you about this fun application of vacuum technology. I recently worked with one of our vacuum customers who services freeze driers for florists, so this topic is “fresh” in my mind. Freeze drying is well-known for use in the manufacturing of food and drugs. Most likely, you have something in your house that has been processed with freeze-drying. So, let’s take a closer look.

 

Freeze dried raspberriesFreeze drying, also known as lyophilization, is a process in which water molecules are removed from biological cells without damaging the cell structure. For starters, the product to be freeze-dried is chilled and the water inside is completely frozen (i.e. placed in the solid state). Next, the pressure is reduced using vacuum pumps and the water molecules sublimate – that is, water goes from the solid phase directly to the gas phase.

 

The gas load due to the water vapor is usually very high and requires condensers to trap the liberated water and stop it from overwhelming the pumping system. Commercial freeze driers (see image below) include a heat exchanger which serves two purposes: first, the heat exchanger is used to cool the product and later, it is used to gently heat the product to drive the water sublimation.

Commercial Freeze DrierView inside commercial freeze-drier

 

Do you know of some other cool applications of vacuum technology, we would “love” to hear from you! Please visit Live chat with us at www.teledyne-hi.com or call 1-800-950-2468.

 

Special thanks to Flowers Forever – Bellabeads for the use of flower image from their beautiful website.

Tags: Vacuum gauge

Carbon Dioxide (CO2)

Posted by Doug Baker on Tue, Feb 09, 2021 @ 03:07 PM

Carbon Dioxide Molecule_1041722966

This blog is the next installment in a series of blogs focusing on industrial gases. The first blog featured SF6 and can be found here:   https://info.teledyne-hi.com/blog/sulfur-hexafluoride-gas-sf6 In this blog, we will explore one of the most useful, and well-known, of the industrial gases, carbon dioxide (CO2).

CO2 is an odorless and colorless gas. As a matter of fact, you exhale about a quarter liter of CO2 every minute (https://www.nytimes.com/1990/08/14/science/q-a-burden-of-breathing.html). And while we are on the subject of breathing, it is interesting to note that it is usually the buildup of CO2 that triggers a breath, not the lack of oxygen. A recent special feature in Gasworld US Edition noted that “low concentrations are not harmful, higher concentrations can affect respiratory function, cause excitation and depression of the central nervous system.”

The structure of CO2 is linear. The electronic structure of the molecule features bonding pairs of electrons around the central carbon atom. These electron pairs repel equally while bonding to oxygen atoms. The equal repulsion is what gives CO2 its linear arrangement. A diagram of the molecule is shown on right.

There are many fascinating uses of CO2, some are well-known while others may be new to the reader.

  • Used in industry to produce chemicals and as feedstock
  • Used in the metals industry to improve the hardness of castings
  • Often used as a carrier for spraying of paints or for spraying vegetable oils in cooking
  • Liquid CO2 can be used as a solvent in eco-friendly dry cleaning
  • Solid CO2 can be used for cold storage
  • Jets of CO2 are used for special effects in movies, live shows, and amusement parks
  • Gas phase CO2 is used for fire extinguishers
  • Carbonated beverages

A quick note on purity... CO2 used for fire extinguishers can be ~ 95% pure. However, the purity of CO2 in carbonated beverages can be as high as 99.9995%.

Hastings CO2 Collage

A word on explosive decompression of elastomers when using CO2. CO2 is known to more easily penetrate elastomeric seals such as o-rings and diaphragms at pressures significantly higher than atmosphere which in turn can cause the host material to swell. If the pressure is suddenly decreased (i.e rapid decompression), the internal gas can rupture the elastomer and the seal can be compromised. There are a few things the user can try to reduce risk. First, select materials that are less susceptible. Viton® is often not a good choice for CO2 applications. Second, if the application will allow, try to reduce the amount of time the elastomeric seal is held at elevated pressure. And third, when the pressure is reduced, allow more time for the CO2 to exit the material.

Flow controllers from Teledyne Hastings are used to measure and control CO2 flow in many of the aforementioned applications. The 300 Vue can provide all-metal seals and Kalrez® valve seat. (see diagram below). For users of the elastomeric-sealed 200 Series, we recommend Buna-N seals which are less susceptible to explosive decompression.

Mass Flow Cutaway

Teledyne vacuum gauges can be used with CO2. The HVG-2020B (Click Here) is an excellent choice for measuring CO2 from below 1 mTorr up to atmosphere. Convection driven pirani vacuum gauges, when used with gases other than N2/air can have curious behavior as can be seen in the cartoon below.

Convection driven pirani vacuum gauges cartoon

The HVG-2020B vacuum gauge uses a gas-independent piezoresitive sensor that does not rely on convection affects and provides a more liner response to CO2 across the entire measurement range.

Piezoresitive sensor cartoon

HVG 2020B Angle Finger 20.9C

 

 

 

 

 

 

 

 

 

If you would like more information about either the 300 Vue mass flow meters or controllers, or any of our vacuum gauges including the HVG-2020B, you can talk to any of our application engineers at 757-723-6531, or email hastings_instruments@teledyne.com or LiveChat with us at www.teledyne-hi.com

Special thanks to Lawrence Ferbee from the stockroom for his cartooning skills. If you would like to see Lawrence in action as he draws these, check out our HVG-2020B video:

https://www.youtube.com/watch?v=_Bk3Q7SpSUc

Viton® is a registered trademark of DuPont Performance Elastomers

Kalrez® is a registered trademark of DuPont Dow Elastomers

Liquefied Nitrogen use in Aluminum Extrusion

Posted by Wayne Lewey on Tue, Nov 24, 2020 @ 12:22 PM

The use of Liquefied N2 (LN2) has revolutionized aluminum extrusion mold performance. CVS Corporation based in Gimpo, South Korea has developed a proprietary LN2 cooling process that allows production output to more than double for some extrusion profiles. Production times vary based on the geometry of the extrusion profile. Ram speed test data can be found in Figure 1 below.

Extrusion Profile Table

Figure 1: Extrusion Profile Table

 

The Aluminum Extrusion Mold Liquid Nitrogen Cooling System from CVS is designed to control the temperature of both the profile and the mold during the extrusion process. As the billet passes through the extrusion mold, the friction between the billet and the mold creates excess heat. This excess heat limits the extrusion ram speed and is the main cause of reduced productivity in the extrusion process. The CVS process maintains optimum profile and mold temperatures by using automated cryogenic proportional control valves to provide precision dosage of Liquefied N2.

Aluminum Extrustion Mold Liquid Nitrogen Cooling System from CVS

Figure 2: Aluminum Extrusion Mold Liquid Nitrogen Cooling System from CVS

Model DCVT-6 Vacuum Gauge with DV-6R

 

 

Figure 3: Model DCVT-6 Vacuum Gauge with DV-6R

To deliver LN2 to the system, CVS employs their own efficient design of vacuum insulated pipe. This design incorporates the model DV-6R thermocouple gauge tube to monitor the vacuum jacket pressure. Mr. Ko Hwa-Jin specified the model DV-6R because of its proven reliability. The CVS production team uses the model DCVT-6 vacuum gauge in conjunction with the DV-6R in manufacturing.

For more detail on effective vacuum jacket insulation, see Teledyne Application Note: Ensuring a Vacuum Jacket is Working Properly​

Mr. Ko Hwa-Jin is the President of CVS Corporation and can be reached by email or website: www.ln2doser.com

Mr. Yoonk Min is the President of Inforad Corp. which is the distributor for Teledyne Hastings Instruments for South Korea. Mr. Min can be reached by email or website: www.inforad.co.kr

Wayne Lewey is the International Sales Manager at Teledyne Hastings Instruments and can be reached by email

Tags: Vacuum gauge, Vacuum Insulated Pipe, Liquefied Nitrogen, Vacuum Gauge Tube, Aluminum Extrusion

Did you know... The 300 Vue mass flow controller has flexible analog and digital output?

Posted by Doug Baker on Thu, Nov 12, 2020 @ 04:26 PM

Did you know? Even if your flow controller does not have the color touchscreen display, the 300 Vue flow line still allows you to switch between analog & digital control by using the zero button. (See the diagram below). You can also toggle between RS232 & RS485. This is a convenient feature when users want to switch their setup. Instructions can be found in the manual (pg. 14).

 

And, of course, we have our free Windows™ software. With the software, you can quickly configure and control your 300 Vue. And you can also record flow data and store to a file If you would like us to send a secure transfer download link for the free software, click here: https://www.teledyne-hi.com/resource-center/software

        300 Vue Top Cover             Vue_Touch_Screen-2

 

Tags: mass flow controller, mass flow instruments

How do I use GCF (Gas Conversion Factors) with my mass flow meter or mass flow controller?

Posted by Doug Baker on Mon, Nov 02, 2020 @ 09:54 AM

Using thermal mass flow instruments by Teledyne Hastings is an easy way to quickly and accurately measure gas flow. And in some cases, a mass flow instrument may be calibrated for one gas, but then the user may want to use the instrument in another gas. In this blog, we will show how to use GCFs (Gas Conversion Factors) when using flow instruments in different gases.

Before we get into GCFs, let’s quickly review the operation of one of our flow sensors. Below, we show a diagram of the 200 Series flow sensor. In this sensor, gas flows through a capillary tube which is heated in the middle to a temperature which is approximately 130°C. Two thermocouples, one upstream (TC-1) and one downstream (TC-2), measure the temperature. The temperature difference between the two thermocouples is proportional to the heat flow through the capillary tube. The heat flow, in turn, is proportional to the mass flow times the specific heat Cp of the gas. So, to first order, if we want to use a thermal mass flow meter that has been set up for one gas, and use it with another gas, we will multiply the output of the meter by the ratio of the specific heats. GCF ~ Cp1 / Cp2

200 Series Sensor

There are a couple of things we need to point out. First, the ratio shown above is a simple approximation and does not tell the whole story. Next, the best GCFs are those that have been measured experimentally. However, in the case of dangerous gases, we use the best thermodynamic data available.

Here is a table of some common GCFs.

Gas Conversion Factors (N2)
  200 Series 300 Series
Helium 1.402 1.400
Oxygen 0.981 0.978
Carbon Dioxide 0.743 0.753
Carbon Monoxide 1.001 1.001
Methane 0.770 0.779
Ammonia 0.781 0.781
Hydrogen 1.009 1.004
Argon 1.401 1.405

Next, we will discuss how we apply GCFs in practice. Let’s take an example of a flow meter that is calibrated for nitrogen. If we wanted to use the flowmeter in argon, we would take the output and multiply by the GCF for Argon.

Argon GCF

Here is another example; suppose we have a meter that is calibrated in helium and we want to use it in hydrogen. You would start by dividing the output by the GCF for helium (think of it as converting to the nitrogen equivalent), and then multiplying by the GCF for hydrogen.

H2 He GCF

Remember, always use the appropriate set of GCFs for the flow series that you are using. In other words, if you are using our Digital 300 Series, don’t apply GCFs from a 200 Series manual – they are not the same. And certainly don’t use non-Teledyne table of GCFs for use with Teledyne flow products. They might get you in the ballpark, but they will not be your best conversion.

One other quick note about applying GCFs. Our line of flow power supplies, the THCD-101 (single channel) and the THCD-401 (four channel), can be used to quickly scale the analog input which is equivalent to applying a conversion factor. Let’s take another look at the Argon example. If we used the THCD-101 power supply with the nitrogen flow meter as shown below, at the nominal full scale of the flow meter, we will have a 5 VDC signal. If we want to use this same meter and power supply with Argon, we just need to “tell” the THCD-101 what value to display when it receives 5 VDC. So, if our flow meter was calibrated for nitrogen to give 5 VDC at 250 sccm, then the same flow meter will give 5 VDC in argon at 350 sccm. (250 * 1.4 = 350). So, we would then range the THCD-101 for 350 sccm. This can be done from the front panel or via the internal webserver.   

HFM200 with THCD

Now let’s make things a little more interesting and discuss a flow controller example. Analog flow controllers work by receiving a command signal (usually 0-5 VDC, or 4-20 mA) and then they adjust their control valve such that the flow, and thus the analog signal output, matches the command signal input. (You can think of it like the cruise control in your car – you tell it you want to go 78 miles per hour, and then the engine does what it needs to do to maintain that speed). In the case of a 0-5 VDC flow controller, a 5-volt setpoint command is instructing the flow controller to set the flow to 100% of full scale. The relationship between flow rate and command signal is linear, so if the user wanted to control at 25% of full scale, then they would send a 1.25 VDC command signal (0.25 * 5 VDC = 1.25 VDC).

HFC with THCD

Now, suppose we had an HFC-202 flow controller (200 Series) that was calibrated for 200 sccm of methane and we wanted to use it to control the flow of argon. What voltage level would we need on the command signal to have a flow rate of 100 sccm of argon? Let’s first determine the full-scale flow rate (5 VDC) when using argon:

Flow (Ar) = Flow (CH4)/GCF (CH4) * GCF (Ar) = (200 sccm / 0.77) * 1.401 = 363.9

So, a 5 VDC command signal will give us 363.9 sccm of argon. If we want 100 sccm, we would send:

Command Voltage = 100 sccm (5 VDC / 363.9 sccm) = 1.374 VDC.

Now, one important note about using flow controllers in different gases. Just because we can apply GCFs does not mean that a flow controller’s valve will work properly when switching from one gas to another. As an extreme example, a flow controller valve that has an orifice sized to handle hydrogen will have a hard time handling significant flows of large polyatomic molecules like C2H6.

Teledyne flow products are easy to install and use. And our application engineers are standing by to help. We can be reached by email (hastings_instruments@teledyne.com), by phone 757-723-6531, or via LiveChat on our website www.teledyne-hi.com or by clicking the contact us button below.

Contact Us

Tags: Flow Meter, mass flow conversion, mass flow controller, mass flow meter, Gas Conversion

Sulfur Hexafluoride Gas (SF6)

Posted by Doug Baker on Wed, Jul 29, 2020 @ 03:14 PM

Over the next several blogs, we will be discussing various industrial gases. While some of these (carbon dioxide, argon, methane, and hydrogen) may be very familiar to our readers, other gases may not be as well known. In this blog, we will take a look at sulfur hexafluoride (SF6), a gas that is one of the most important today in the utility industry.

SF6_v2

SF6 is an interesting gas primarily because of its electrical properties. Certain neutral gas molecules can easily capture free electrons and form stable negative ions. The efficiency of negative ion formation in a gas is determined by its electron affinity. SF6 , it turns out, has a very high electron affinity and therefore has excellent electrical insulating strength. So, in an electrical discharge inside a volume containing SF6 gas, the free electrons generated by the discharge are captured by neutral SF6 to form negative ions. These large negative ions are not able to travel quickly and so the discharge is usually quickly extinguished. One other note about SF6, the insulating property of the gas improves with increasing pressure. SF6 is colorless, odorless, non-toxic, and non-flammable. As you can see, these properties make it very useful to the generation, transmission, and distribution of electricity. 80% of the world’s SF6 gas is used by electrical utilities in circuit breakers, transformers, and gas insulted switches.

SF6 is arranged in a hexagonal structure. Each of the six fluorine atoms shares two its electrons with the outer shell of the sulfur atom in the middle. This structure gives SF6 its stability over a broad range of temperatures; the gas is thermally stable up to 500°C.

 

Power Substation

SF6 is often used in high voltage breakers. One example is the so-called dead tank breaker. In a dead tank breaker, the tank is electrically tied to earth/ground. In the live tank version, the tank is floating at a higher voltage.

 

The “make/break” mechanism of the breaker is shown in the diagram below. As noted above, the insulating properties of SF6 are improved with increasing pressure. So one of the jobs of the breaker’s piston actuation is to compress the SF6 gas and force it to flow into the arc region. As the contacts are moved apart, current will try to continue to flow as an arc. Any resulting arc is quickly extinguished by the pressurized SF6 flowing into the region. Incidentally, during breaker manufacturing, vacuum gauges from Teledyne Hastings are used to measure vacuum levels inside the vessel during pump down as the air is removed. After evacuation, the region can be filled with SF6.  

SF6 Circuit Breaker

OK, one last note about SF6 to conclude this blog and this falls under the category of “Don’t Try This at Home.” Just like Helium will make your voice sound higher if inhaled, SF6 will make your voice sound lower. You can find many demonstrations of this on YouTube. The most famous example is probably the demonstration on “The Big Bang Theory.” However, SF6 is one of the most powerful greenhouse gases and its release into the atmosphere should be minimized.

 

300 Vue Gas screen-1

Teledyne Hastings builds both vacuum and flow instrumentation which can easily work with SF6. Note that SF6 has a very high thermal conductivity. Conceptually, this makes sense because the gas molecule has many degrees of freedom – translational, rotational, and vibrational.  The GCF (gas conversion factor) for SF6 use with the 300 Vue line of flow controllers is 0.27. In other words, if you wanted to use a 300 Vue mass flow meter that had been set up for nitrogen, you would need to multiply the output by the 0.27 GCF. The good news for you is that with the 300 Vue, you can just select the gas from the front panel as shown in the photo below. Just keep in mind that if you wanted to do this, the required pressures for the valve are going to be different. You will likely need a higher pressure drop. But as always, our application engineers can be reached by email, phone, or Live Chat on our website: www.teledyne-hi.com

How Vacuum Gauges are used in the production of Neon Lights

Posted by Doug Baker on Wed, Jul 01, 2020 @ 01:48 PM

Several months ago, I saw an interesting article about a cool museum called the Neon Museum which is located in Las Vegas.

https://www.neonmuseum.org/

According to the museum’s website, “the Neon Museum is a non-profit 501 (c) 3 organization dedicated to collecting, preserving, studying and exhibiting iconic Las Vegas signs for educational, historic, arts and cultural enrichment.” The museum holds over 250 neon signs. Tours are given both day and, of course, at night. The main collection in the “Bone Yard” includes signage from Caesar’s Palace, The Stardust Resort and Casino, and the recently added giant guitar from the now closed Hard Rock Café.

Some of the pieces are still operational and “live” shows are given nightly. Other signs are dormant and are lit up by flood lights.

Composite

(Photos Courtesy of the Neon Museum, Las Vegas, NV)

 

Production of neon light tubes requires vacuum pumps and, of course, reliable vacuum measurement. Typically, glass tubes are bent into shape and then pumped to around 1 Torr and energized using a glow discharge to clean up the tube. Next, the tube is evacuated to the mTorr region. Different gases are then backfilled to a few Torr which, when excited in a glow discharge, create various colors. Neon gives the classic neon red/orange glow while carbon dioxide produces white, helium gives yellow, and mercury can be blended with neon to produce blues. In some cases, coatings on the internal surface of the glass can be used to create additional colors. When using coatings, mercury is included in the gas to ensure that UV photons are created to activate the fluorescent coating.

A nice tutorial of glow discharge characteristics with some history is given starting on page 14 in the February 2020 issue of Vacuum Technology & Coating magazine.  https://digital.vtcmag.com/12727/26337/index.html

HVG 2020B Angle Finger 20.9CThe new HVG-2020B from Teledyne Hastings is a great vacuum gauge for this application. The gauge uses two vacuum sensors: a piezoresistive sensor to measure pressures from atmosphere to 10 Torr and a thermal Pirani sensor to measure from 1 Torr to 0.1 mTorr. In between 1 and 10 Torr, the gauge uses a weighted average to ensure a smooth transition between the two sensors. The piezoresistive sensor is gas species independent, so no matter what gas is being backfilled, the piezoresistive sensor gives an accurate measurement. The Pirani sensor’s response is affected by the gas species, but the user can select a gas and the correction is made.

 

So, the next time you see a neon light, you can think about the vacuum gauge that was probably used to manufacture the gas tube. And if you’re ever in Vegas, check out the Neon Museum!

 

For more information about any of our vacuum gauges or our complete line of mass flow meters and controllers, we are here to help. You can contact us at hastings_instruments@teledyne.com , Live Chat on our website www.teledyne-hi.com , or call 757-723-6531 (800-950-2468). And to learn more about the HVG-2020B Vacuum Gauge, click the link below, “5 Reasons you need the HVG-2020B Vacuum Gauge.”

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Tags: Vacuum gauge

Introducing our Newest Product - THCD-401 4-channel power supply

Posted by Devin Seran on Thu, Mar 05, 2020 @ 03:51 PM

Figure 1- THCD-401 Teledyne Hastings is proud to announce our newest 4-channel power supply, controller and display, the THCD-401. The THCD-401 provides both ±15 VDC or 24 VDC to power our mass flow controllers, flow meters, vacuum gauges and pressure transducers. Feedback from connected devices is displayed on the bright, front panel LED display in 6-digit resolution, making open and closed channels easily identified at a glance. The THCD-401 can set a relay point for control of other processes and has a high accuracy of ± (0.02% of Reading + 0.01% of Full Scale). Custom configuring our products to customer needs is our specialty. Your THCD-401 can be factory configured to match the gas, range, units and the output of your instruments for out-of-box functionality.

What’s Improved?

In short, the THCD-401 was designed for exceptional user access and control.  The addition of a circular touch pad simplifies navigation through the unit’s various menu options, while left and right arrow keys allow easy selection of digits to be changed. Calibration is no longer needed for various levels of input voltage and built-in fuses provide additional surge protection.  Back panel communication ports have been streamlined and a USB-C and Ethernet port for serial communication have been added. 

Ethernet Starburst-1The addition of Ethernet communication provides access to the newest feature that the THCD-401 has to offer; the internal web server! The web server can be accessed by entering the IP address of the THCD-401 into a browser’s address bar (requires static IP address configuration on the network prior to use). While the web server feature works best in Mozilla™ Firefox®, it can be accessed via any browser you choose.  Figure 2 shows the web server interface with applications along the top navigation bar and a live data stream for remote read.

The web server allows you to name channels and adjust the range or units based on your device and the full scale (V) voltage output that it sends. This enables users to see the flow rate of a flow controller or meter, as well as the ability to OPEN/CLOSE all channels at the click of a button. Other applications include linearization, setting of a relay point and finding the total amount of gas that has passed through the device using the totalizer function.
Figure 2 - New web browser interface for THCD-401

It should be noted that while all these advanced features are available via the web server (Ethernet) connection, the THCD-401 also offers direct access to each via the front panel display menus using the circular touch pad.  This allows for quick and convenient setup of the channel’s full scale and range(V) for new devices.

If a relay point has been tripped, it will be indicated to the left of the channel’s name on the THCD-401 display. The display will also show the current mode of the set point, if it is not configured in AUTO mode. In OPEN mode, the set point outputs a voltage greater than the full scale of the device. In CLOSED mode the set point outputs a voltage less than the minimum output voltage of most devices. AUTO mode is dependent on the user defined set point configured through the THCD-401 physical buttons, digital communication or external input. 

More Information:

The THCD-401 was designed to be a highly flexible and multi-featured process display controller that can be panel mounted and capable of interfacing to an assortment of meters, controllers and gauges.  A powerful upgrade from the previous THCD-400 model, the THCD-401 adds digital communications, a bright LED display and a variety of customizable options to an already time-tested platform. To learn more about the
THCD-401 or any of our other vacuum and flow products, contact us at hastings_instruments@teledyne.com, call 1-800-950-2468, or click the button below.

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