Teledyne Hastings Instruments Blog

Thermal Mass Flow Controllers (MFCs) control the mass flow (or more specifically molecular flow) of gases. If we are measuring flow rates, why are there so may pressure specifications? This blog will attempt to explain the various pressure specifications associated with MFCs.

Standard Temperature and Pressure (or STP):

The volume of a gas changes with temperature and pressure changes; therefore, basic volumetric flow units are almost useless when defining gas flow rates. When you pick up an MFC or look at the calibration report, you always find a value for Standard Temperature and Pressure (or STP. For most MFC applications, it will be listed as STP: 0° C & 760 Torr. This does not mean that the MFC must be used at that temperature and pressure. Some gases may not even be in gas phase at those conditions. STP is a way of defining molar volumetric units. STP allows your gas calculations to be correct when you measure all your experimental data using the same STP values.

Maximum Allowable Working Pressure:

The Maximum Allowable Working Pressure (sometimes expressed as M.A.W.P.) represents the maximum working pressure for which the end user is permitted to operate the MFC. There should be a label on the MFC that defines this value. For safety purposes, the end user should never exceed this limit.

Proof Pressure:

The Proof Pressure is the pressure value to which the MFC manufacturer proof tests the unit. This value is typically 1.5 times the Maximum Allowable Working Pressure. For example: if the Maximum Allowable Working Pressure is 500 PSIG, the manufacture may Proof Test the unit to 750 PSIG. Even though the manufacturer tests the unit to this value, the end user is still not permitted to exceed the Maximum Allowable Working Pressure.

Burst Pressure:

Burst Pressure is the maximum pressure that can possibly be applied to the MFC without physical damage to the pressure containment. It’s typically much higher than the Proof Pressure. MFC manufacturers will define this during product development. This can be modelled using 3D stress analysis and eventually tested using a hydraulic pump. Burst Pressure testing tends to be a favorite for most engineers.

Inlet Pressure & Outlet Pressure:

Some people forget that the MFC contains a proportional control valve. To proportionally control the flow, there must be a pressure drop across the MFC. Inlet Pressure (Up Stream Pressure) is the pressure measured exactly at the MFC inlet fitting. Outlet Pressure (Down Stream Pressure) is the pressure measured exactly at the MFC outlet fitting. To facilitate flow, Inlet Pressure must always be greater than Outlet Pressure. Some MFC manufacturers will define these values on the MFC Serial Number label.

Differential Pressure

Differential Pressure is often abbreviated as dP or ΔP.

dP = Inlet Pressure – Outlet Pressure

Pressure Coefficients:

Even though thermal mass flow values are independent of temperature and pressure changes, the thermal mass flow sensor performance is impacted at higher pressures. The flow sensor consists of a small 316SS capillary tube that is wrapped with several windings of heater wire. When the pressure increases, the capillary tube expands. When that occurs, the heater windings expand with the tube. The error associated with this expansion is represented by the Pressure Coefficient. For example, a typical Pressure Coefficient could be +0.0067%/psi. 

To learn more about the Teledyne Hastings Instruments mass flow meters and mass flow controllers, visit https://www.teledyne-hi.com/en-us/what-we-do/thermal-mass-flow 

If you have questions about mass flow controllers, feel free to contact us by phone (+1-757-723-6531 or 1-800-950-2468), email Hastings_Instruments@Teledyne.com, or via Live Chat on our website www.teledyne-hi.com.

We are starting a new blog series where we will introduce you to our authorized service partners. These partners are fully authorized to calibrate and repair Teledyne Hastings Instruments products.

Our first blog in this series will focus on the EMEA (Europe-Middle East-Africa) Service Center, Chell Instruments. Chell is based in North Walsham, England which is on the east coast near Norwich, about a 3-hour drive northeast of London.

Chell Instruments was established in May of 1976 by Ron and Judith Michell, hence the name Chell. They became a distributor for Teledyne Hastings Instruments shortly after in 1977 and began to distribute Hastings’ vacuum gauges, mass flow meters, and mass flow controllers in the United Kingdom and Ireland. Not only is Chell a great distributor, but they also excel at designing and manufacturing their own products and systems. In fact, they have a full engineering team that allows them to provide turnkey system solutions for their customers.

The last component to Chell’s success (and the topic of this blog) is their extensive calibration lab. Chell operates a complete calibration and repair lab capable of servicing instruments that measure Flow (Gas), Vacuum, Pressure, Temperature, and Electrical properties. Chell’s lab is UKAS accredited (fully accredited to ISO/IEC17025:2017). Chell can calibrate and repair nearly all Teledyne Hastings Instruments vacuum gauges, mass flow meters, and mass flow controllers. They also stock spare parts in England to quickly support most mass flow meter and mass flow controller repairs.

CALIBRATION Capabilities:
Flow (Gas):         0.0010 L/min to 1250 L/min (up to 7 bar); Up to 12,500 L/min (at low pressure)
Vacuum:              1x10^-4 Pa / 1x10^-6 mbar / 7.5x10^-7 Torr to 1000 Torr

Complete details can be found at: https://chell.co.uk/calibration

One of the great attributes of Chell is their flexibility. If you have too many instruments to ship to Chell, they will come to you! They offer on-site calibration services for several ranges of instruments, and they offer this service for most of the United Kingdom. Would you like to calibrate your own vacuum gauges? If so, Chell sells a portable vacuum calibration system called the CalCube. Would you like to calibrate your own mass flow meters and mass flow controllers? If so, Chell sells flow calibration standards (Fluke Molbox/Molbloc) and can even manufacture complete flow calibration systems.

For more details about services offered by Chell Instruments, please visit: https://chell.co.uk

Also, be sure to follow Chell on LinkedIn to stay on top of what’s new. Next year will mark Chell’s 50th anniversary, so stay tuned for their big celebration!
https://www.linkedin.com/company/chell-instruments

For more information on calibration services for vacuum gauges, vacuum transducers, mass flow meters, and mass flow controllers provided by Teledyne Hastings Instruments, please check out: https://www.teledyne-hi.com/en-us/what-we-do/calibration-repair

Most people are aware that the HVG-2020B wide range vacuum gauge has an optional display, but not everyone realizes that it's much more than just a display. It's actually a color touchscreen display and is packed with features. Let's take a look.

The HVG-2020B has 5 different display modes. Simply touch the icon on the lower left side to toggle through each one.

Available Views

1. Pressure View: gives the pressure and units. Touching the pressure reading will toggle between decimal notation and scientific notation. Touching the units will cycle through available units (TORR, MBAR, KPA, PSIA, PSIG, ATM, BAR, PA).
2. Pressure and Temperature View: The screen adds a temperature indication. It is only meant to be a visual aid indicating ambient temperature (± 1.5 °C). Touching the temperature will toggle between °C and °F.
3. Setpoint View: The HVG-2020B has two setpoints. This view provides visual indicators of Hi and Lo setpoints. If the indicator is green the setpoint is active. The Hi setpoint is active when the pressure is above its setting and the Lo setpoint is active when the pressure is below its setting. The two settings may be different. Touching the Hi and Lo indicators will bring up a screen allowing the corresponding setpoint to be adjusted. Use the left/right arrows to select the digit and the up/down arrows to change the value of the digit.
4. Bar Graph View: A graphical indication of the current pressure on a log scale. Use it to quickly identify your desired pressure from across the room without having to read a number.
5. Graph View: A graphical indication of the pressure over time. Use it to identify the presence of a chamber leak and differentiate between a real leak and outgassing. Touching the screen anywhere will bring up a screen allowing the user to adjust the time (in seconds) per sample (displayed point). Use the left/right arrows to select the digit and the up/down arrows to change the value of the digit.

Menu Features

There are many more features that can be accessed simply by touching the Menu icon on the lower right side. Useful Menu features include:

• Screen Orientation
• Set Zero
• Device Info
• Analog Output
• Serial Port
• Restore Factory Defaults

One of the most useful features is the ability to change the screen orientation. The HVG-2020B can be mounted in any orientation. This feature allows the user to rotate the screen to a position that is easy to read.

The HVG-2020B is a wide range vacuum gauge that uses both pirani and piezoresistive technology to accurately measure 10^-4 Torr to 1000 Torr. Learn more about the HVG-2020B at:

https://www.teledyne-hi.com/products-services/vacuum-measurement-and-control/hvg-2020b

Time for another blog in our “Employee Spotlight Series.” This time we will meet Chris Bracey. Chris started at Teledyne this past September, and he is a Regional Sales Manager.

Let’s ask Chris some questions and get to know him better.

You’re still somewhat new to Teledyne. Tell us a little about your career prior to joining Teledyne.

I started off with CONCOA in Virginia Beach. They manufacture pressure regulators and gas delivery systems. I was there for a few years and did mostly R&D work. I later worked for Flowserve where I worked on the fluid side of the business as a Customer Service Engineer. That’s where I started moving from Design/Development to the Customer Support side of the business. After that, I had an opportunity to be an account manager for Usui International which is an automotive supplier. They provide high pressure fluid distribution systems. I spent 16 years managing large household name accounts like Cummins, John Deere, Volvo/Mack Trucks, and others. From there, I became the Sales Manager for Asheville Mica and got exposed to the Electric Vehicle industry. I got to work with the development of battery safety blanket systems to prevent runaway EV battery fires.

Tell us a little about your educational background.

I started with an associate degree in drafting. I received a BS in Mechanical Engineering Technology from Old Dominion University. I was later able to complete an MBA with focus on Sales & Marketing also at Old Dominion University.

What do you do here at Teledyne?

I’m the Domestic Regional Sales Manager. I manage our domestic sales channel partners. My role is to support the sales team and our sales channel partners in the field. I’ve been assisting with quotes and sales orders, and I’ll start traveling with our sales force in February.

What’s been the most challenging thing to learn since you joined Teledyne?

There’s a lot to learn. I spent some time in the service department servicing and recalibrating mass flow controllers and vacuum gauges. I’ve also spent a lot of time selecting and sizing flow controllers.

You attended the 2024 Teledyne Hastings distributor training session in October. What were your takeaways?

I quickly found out that I knew more about vacuum gauges and flow controllers than I realized. Working with the service team gave me a great background before going through the sales training. I also got a chance to meet several reps that I may not have met until later down the road. It was nice to meet lots of people in one place before I had a chance to get around to their individual locations.

Outside of work, what do you like to do?

I like to restore cars and motorcycles. I also do home renovation projects. I’m currently building a pantry in my kitchen. I can do electrical, drywall, and whatever needs to be done. I’m currently restoring a 1990 Miata that was parked for a while. I’m also working on two motorcycles: a Kawasaki KZ1000 (1977) and a 1976 Triumph Bonneville Chopper. I also like to read and listen to a lot of audiobooks when not reading auto manuals and schematics. I prefer mostly business & self-help and some science fiction.

Check out more from our blog and read more about our vacuum gauges and mass flow meters and mass flow controllers (and be on the look out for future postings about Teledyne Hastings' employees.)

Thermal mass flow measurement instruments are typically separated into two main categories: Mass Flow Meters and Mass Flow Controllers. It’s estimated that over 90% of mass flow measurement instruments sold are mass flow controllers. So, it’s no surprise that most mass flow application conversations focus on mass flow controllers. Notwithstanding, there are still numerous applications for which mass flow meters are critical.

The following are common applications for mass flow meters (also known as thermal mass flow meters):

One popular application for mass flow meters is leak testing. It’s often used on products where failure is not an option. For that reason, it is widely accepted in the aerospace, automotive, and medical industries. High throughput leak detection using mass flow meters is a nondestructive testing method that offers a fast, clean, precise, and affordable solution for parts manufacturers seeking to perform leak testing on 100% of their products.

A typical test stand is shown in Figure 1. For high throughput leak detection, a pressurized manifold has multiple connections for mass flow meters. On the outlet side of each flow meter is an isolation valve and the test part. When the isolation valve is opened, test part leaks will be noted by the movement of clean dry air across the flow meter. The test part is only exposed to clean dry air.

How does leak detection with mass flow meters compare to alternative methods? It’s faster than pressure decay testing and helium leak detectors. It’s also cleaner than hydrotesting, bubble testing, and liquid penetrate testing.

To learn more, visit our Application Note:

https://www.teledyne-hi.com/resourcecenter/Application%20Notes/PB-172-High_Throughput_Leak_Testing.pdf

Common products for which high throughput leak detection has been implemented include:

• Automotive Parts such as fuel injectors, brake components, exhaust systems, emission components, fuel pumps, fuel tanks, power steering systems, air conditioning systems, engine blocks, cylinder heads, transmission castings
• Aerospace Parts such as jet engine components, heat exchangers, cabin valves, oxygen delivery systems, hydraulic systems, air conditioning systems, brake systems
• Other: medical devices, filters, space suits, and much more
  
  

​

Frequently Asked Questions (FAQS)

Q: What’s the difference between a thermal mass flow meter and mass flow controller?

A: A thermal mass flow meter measures flow using a thermal flow sensor but does not include a proportional control valve and does not control gas flow. While a thermal mass flow controller will both measure and control gas flow, according to a command signal (setpoint). For accurate flow control, the controller measures and adjusts the gas flow using a precise, proportional control valve to maintain stable control of the flow rate based on the readings from the heated sensor.

Q: Are thermal flow meters gas specific?

A: A thermal mass flow meter is built for a user’s specific operating conditions. Teledyne Hastings' thermal flow meters are thermal based, so measurements are gas specific. For example, there would be a difference in heat conductivity between natural gas vs compressed air. Our thermal mass flow meters are built to cover a user's flow range and gas type. 

​Q: What does SCCM stand for?

A: SCCM stands for Standard Cubic Centimeters per Minute. This is a unit of measure for gas molecular flow rate (often referred to as mass flow). In standardized volumetric flow units, the reference conditions, or “STP" temperature and pressure, define the amount of gas by determining the number of gas molecules using the Ideal Gas Law.

Time for another blog in our “Employee Spotlight Series.” This time we will meet Rob Milversted. Rob has worked for Teledyne for over 20 years, and he is the Director of Sales for Process Instruments and Systems (Teledyne Hastings Instruments and Teledyne Analytical Instruments).

Let’s ask Rob some questions and get to know him better.

Tell us a little about your background.

I’m a SoCal boy. I’ve lived most of my life in Chino. I attended Cal Poly Pomona and studied Electrical Engineering as an undergrad. I was always shocking myself with things around the house a as kid, so Electrical Engineering just seemed right.

Tell us about your start at Teledyne.

I got a job as an Electrical Engineering Intern at Teledyne Analytical Instruments (TAI) while still in college. In 2002, I was able to join Teledyne full time as an Electrical Engineer. Teledyne allowed me to complete my MBA (also at Cal Poly) while working. I shifted to sales and held multiple sales and sales management positions. In 2021, I was promoted to Director of Worldwide Sales for Teledyne Analytical Instruments and Teledyne Monitor Labs. In 2023, I became Director of Sales for Process Instruments and Systems (Teledyne Hastings Instruments and Teledyne Analytical Instruments).

What is your current role at Teledyne?

As Director of Sales, I have global product sales responsibility for TAI and THI products. I oversee Regional Sales Managers in North America, and I share sales responsibility with our Directors of Sales in APAC and EMEA.

Outside of work, what do you like to do?

I spend lots of time getting my three kids to extracurricular activities. There’s not much free time. My family is heavily involved in Girl Scouts and Boy Scouts. We do a lot of camping. I also enjoy catching NFL games when I can.

What is your favorite thing about working at Teledyne?

The best thing about Teledyne are the people that work here. Everyone I know works extremely hard and wants to help customers. Everyone is like family. I now meet coworkers from other parts of Teledyne, and I wish I’d met them sooner.

Check out more from our blog and read more about our vacuum gauges and mass flow meters and mass flow controllers (and be on the look out for future postings about Teledyne Hastings' employees.) 

The HVG-2020B wide range, dual sensor vacuum gauge takes measurement to the next level. With a Piezo based sensor and a thermal based Pirani sensor, it accurately and confidently measures pressures across seven decades. The Piezo sensor is media isolated, gas composition independent, and periodically zeroed by the Pirani sensor. An ambient thermal sensor enables the instrument to adjust for temperature and therefore better accuracy.

The HVG-2020B offers multiple linear and logarithmic analog output signal options.

Why do you think we offer so many logarithmic output options?

The linear output may not always be useful. Remember: the HVG-2020B is a wide range gauge that covers seven (7) decades of vacuum. That’s a huge range to cover with a linear output signal!

For example, if you are using 0 – 10 VDC Linear Output:

• At 1000 Torr, the output will be 10 VDC
• At 760 Torr, output will be 7.60 VDC
• But at 1 mTorr, voltage output will only be: 0.00001 VDC

We offer the logarithmic output options to provide better resolution throughout the curve.

Our default output option (recommended option) is the Logarithmic Option (08): 2 – 9 VDC (1 VDC / decade)

If you read Voltage (V), you can quickly calculate Pressure (P):

P = 10^{(V_out - 6)}

Complete linear and logarithmic output options for the HVG-2020B include:

There are analog output signal options to match most common pirani vacuum gauge outputs as well as a non-linear curve based on convection style vacuum gauges. It is also possible to generate a custom user-defined logarithmic output (see section 5.2.8 of the manual).

In addition, the HVG-2020B offers an optional color touchscreen display, free Windows data acquisition software, and a variety of digital communication paths that make the HVG-2020B flexible and user friendly. Whether you need USB, RS 232, RS 485, linear or log outputs, graphical displays for data acquisition logging, this wide range gauge can perform.

You can request the software from our website. Please find the link here: https://www.teledyne-hi.com/resource-center/software

In addition to the windows software, we also have a certified LabVIEW driver.

HVG-2020B Vacuum Gauge LabVIEW Driver – Click Here

As always, we are here to help. If you have any questions about any of our vacuum or flow products, you can reach out to us by phone (800-950-2468/757-723-6531), email (hastings_instruments@teledyne.com), or via LiveChat on our website (www.teledyne-hi.com).

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When selecting a flow meter or flow controller for gases, it is important to understand the difference between the mass flow rate and volumetric flow rate. Unlike liquids, gases do not have a constant volume. The volume of a gas changes as the temperature and pressure change.

Referencing the Ideal Gas Law: PV=nRT

• When the temperature of a gas increases, the volume increases.
• When the temperature of a gas decreases, the volume decreases.
• When the pressure of a gas increases, the volume decreases.
• When the pressure of a gas decreases, the volume increases.

When you only know the volume or volumetric flow rate of a gas, you may not actually know how much gas you have. In this blog, we compare mass flow rate vs volumetric flow rate, how each are measured, and the advantages of each.

What is Mass Flow?

Hastings’ first thermal mass flow meter was introduced in the 1960s, and the phrase “mass flow” has been commonly used. However, the phrase “mass flow” is a bit of a misnomer. Thermal mass flow meters actually measure the flow rate of gas molecules or the molecular flow rate. Since the mass flow meter or controller measures the molecular flow rate, it is independent of temperature and pressure changes. It is not necessary to separately measure temperature and pressure, and temperature and pressure corrections are not required.

Teledyne Hastings Instruments mass flow meters and mass flow controllers use a thermal flow sensor to measure the molecular flow rate. The flow sensor is heated, and the flowing gas molecules transfer or “carry” the heat downstream. The rate of heat transfer is proportional to the mass / number of gas molecules flowing through the sensor which is used to determine the flow measurements.

Mass flow rates can be expressed in true mass flow units such as LB/hr, Kg/hr, and g/sec. However, they can also be expressed in standard volumetric flow rates such as SCCM, SLM, and SCFM. Standard volumetric flow units look like volumetric flow units, but they are mass flow units. Standard units are referenced to Standard Temperature and Pressure (STP). STP must always be defined. Teledyne Hastings Instruments typically uses STP: 0° C & 760 Torr; however, other STPs can be specified.

What Should Mass Flow Rate be Used For?

Mass flow rate measurement is ideal for any application where gas measurement is critical. As stated earlier, there is no need to simultaneously measure gas temperature and gas pressure which can introduce errors to your calculations. It’s ideal for applications requiring fast, reliable, repeatable, and accurate measurements.

Some common applications include instrument calibration, air sampling, non-destructive leak testing, gas blending (mixing), thermal spraying, thin film deposition, analytical instrumentation, and many more.

What is Volumetric Flow?

Volumetric flow rate is mathematically defined as the cross-sectional area of a tube multiplied by the velocity of the fluid. It simply measures volume per unit of time. Volumetric flow is ideal for liquids since their volume mostly cannot change. When using volumetric flow meters for gas measurement, the only way to determine how much gas is flowing is to calculate it. That requires either maintaining constant temperature and pressure or simultaneously measuring them. Examples of volumetric flow methods include rotameters, turbine meters, and critical orifices.

One of the most common volumetric flow meters is a rotameter or variable-area flow meter. It consists of a tapered tube and a float. The tapered tube is typically constructed of glass to allow the user to visually see the float. As the flow rate increases, the float travels up the tapered tube. The tube has graduated lines to indicate the volumetric flow rate.

Some common volumetric flow units are GPM, L/s, and CFM. Mass flow can be calculated from volumetric flow only if the density (ρ) is known. Q_mass = Q_vol*ρ.

What Should Volumetric Flow Rate be Used For?

Volumetric flow rates are fine in applications where the volume is constant such as incompressible liquids. They can also be found in gas applications where the temperature and pressure are fixed. In addition, volumetric flow meters typically have a lower initial cost than a mass flow meter. They are often found in low-cost gas measurement applications where molecular flow rate accuracy is not critical. When molecular flow rate accuracy is required, the user typically measures temperature and pressure separately and calculates it.

Summary

Both mass flow meters and volumetric flow meters are commonly used to measure gas and liquid flow measurements. For gas flow measurement, mass flow is more trusted as it measures the gas molecular flow rate. Mass flow meters and controllers function independently of gas temperature and gas pressure changes. This makes mass flow meters and controllers ideal for applications requiring fast, reliable, repeatable, and accurate measurements. Volumetric flow meters such as rotameters or critical orifice devices cannot routinely achieve these high accuracy levels on gases due to inherent inaccuracies and variations that occur as a result of pressure and temperature changes.

FAQS

• Q: Can Teledyne Hastings’ flow meters be used with liquids or any fluid?  
  A: No. Teledyne Hastings’ flow meters cannot be used with liquids. A fluid is defined as “a substance without a shape and can be either a gas or liquid”. Fluids used in our flow meters must be in the gas phase (gases only).

• Q: What is STP (Standard Temperature and Pressure)?
  A: In standardized volumetric flow units (SCCM, SLM, SCFM), the reference conditions, or “STP” temperature and pressure, define the amount of gas by determining the number of molecules using the Ideal Gas Law. In most cases, the selected reference conditions are 0°C & 760 Torr. Other reference conditions are also used, such as 20°C & 760 Torr, or 70°F & 760 Torr.

• Q: What does SCCM stand for?
  A: SCCM stands for Standard Cubic Centimeters per Minute. This is a unit of measure for volumetric flow. In standardized volumetric flow units, the reference conditions, or “STP" temperature and pressure, define the amount of gas by determining the number of gas molecules using the Ideal Gas Law.

Calibration is the cornerstone of measurement accuracy, ensuring that instruments deliver reliable and precise data. Thermal mass flow meters play a pivotal role in providing a dependable solution for various industries. The calibration of these instruments is a critical factor that demands meticulous attention. In this blog, we delve into the intricacies of thermal mass flow calibration, unraveling the science behind it and its significance in achieving accurate measurements.

The Basics: What is Thermal Mass Flow Meter Calibration?

Teledyne Hastings’s flow meters and flow controllers use thermal mass flow sensors. The Teledyne Hastings Instruments 200 Series thermal mass flow meters operate on the principle of heat transfer using thermocouple technology. The flow sensor consists of a capillary tube that is heated at the midpoint. Thermocouples are used to measure the temperature on both the inlet and outlet ends of the tube. As gas molecules travel through the flow sensor, heat is transferred downstream. The temperature differential between inlet and outlet correlates to the molecular flow rate of the gases. The molecular flow rate is directly proportional to the mass flow rate of the fluid. This relationship forms the basis for the calibration process, as accurate calibration ensures that the meter provides reliable measurements across a range of flow rates and conditions.

Calibration is indispensable for maintaining the accuracy and reliability of thermal mass flow meters. Over time, factors such as contamination, sensor degradation, environmental changes, or wear and tear can impact the meter's performance. Calibration allows for the correction of these deviations, ensuring that the meter consistently produces accurate readings. Moreover, many industries are subject to regulatory standards that mandate regular calibration to guarantee the reliability of the data collected.

How To Calibrate Your Mass Flow Meter

1. The first step in thermal mass flow calibration is establishing a reference standard. This is typically a device with a known and traceable accuracy. The reference standard is used to compare and verify the accuracy of the mass flow meter being calibrated. This can be a reference standard or another flow meter. A high accuracy 300 Vue thermal mass flow meter or mass flow controller with local touchscreen display would create a standard that the unit under calibration will match to.
   
   
2. Calibration involves subjecting the flow meter to controlled flow rates covering its entire operating range. The meter's response to these different flow conditions is carefully observed and compared to the reference standard. The best calibration would be used with actual gas to get the most accurate data points. Since the actual gas (e.g. Helium) could be expensive or rare, then a more accessible gas such as N2 or Air is used with a conversion factor to calculate the actual flow rate in the desired gas.
   
   
3. As the flow meter undergoes calibration, data on its performance at various flow rates is collected. This data is then analyzed to identify any deviations from the reference standard. The reference temperature and pressure may differ from the actual process temperature and pressure. Calibration software may be employed to streamline this process.
   
   
4.  If discrepancies are detected, adjustments are made to the thermal mass flow meter to correct its readings. This may involve recalibrating sensor elements or updating compensation factors. The goal is to align the meter's measurements with the reference standard. It is important to note how large these discrepancies are as it may require repair instead of calibration.

In the world of fluid dynamics and process control, selecting the appropriate flow measurement parameter is crucial for accurate and reliable data. Teledyne Hastings’s uses heat transfer technology to indirectly measure the molecular flow rate of dry gases. Our instruments can be used with volumetric flow units as they are converted to find the mass flow rate.

What is the Thermal Mass Flow Meter Working Principle?

Basic Design:

A mass flow meter consists of four basic components:

1. Electronic Circuit Board
2. Flow Sensor
3. Bypass Shunt
4. Base

*See Figure on right

In the world of fluid dynamics and process control, selecting the appropriate flow measurement parameter is crucial for accurate and reliable data. Teledyne Hastings’s uses heat transfer technology to indirectly measure the molecular flow rate of dry gases. Our instruments can be used with volumetric flow units as they are converted to find the mass flow rate.

There are numerous thermal mass flow sensor designs.  The Teledyne Hastings’ 200 Series sensor is shown in image on left.  This thermal mass flow sensor consists of a small 316SS capillary tube with a heater winding located in the center.  A thermocouple (TC-1) is located on the inlet side and another thermocouple (TC-2) is located on the outlet side.  At zero flow (no gas flow), the heat is transferred through the capillary tube in both directions towards the two thermocouples, each of which has the same temperature (see image on right, ZERO FLOW condition).  As gas flow moves through the capillary tube (inlet to outlet), heat is then transferred downstream by the gas molecules.  The temperature of TC-2 will increase, while the temperature of TC-1 will decrease.  This temperature differential correlates to the molecular flow rate of the gases (mass flow). 

Output:

A majority of thermal mass flow meters provide an analog output signal (0-5vdc, 4-20mA, etc.) that is directly proportional to the gas flow rate.  System integrators can directly acquire this signal for process control.  

If the installation is not configured for data acquisition, Teledyne Hastings offers convenient power supplies with integrated displays (see models THCD-101 and THCD-401 in image on right) and ready-to-use connector cables for quick start-up.

Some mass flow meters offer digital communication to convey the flow rate, while other models have a built-in color touchscreen display (See model HFC-D-302B Vue in image on left).​

Thermal Mass Flow Meter Advantages

Thermal mass flow meters have gained widespread popularity in various industries due to their numerous advantages in measuring the flow of gases. Let's explore some of the key advantages of thermal mass flow meters:

One of the primary advantages of thermal mass flow meters is their ability to directly measure mass flow rate. Unlike other flow measurement methods that may require additional measurements or assumptions about fluid properties, thermal mass flow meters provide a direct and accurate measurement of gas flow.

Thermal mass flow meters are less affected by variations in pressure and temperature compared to some other flow measurement technologies. This robustness allows for accurate measurements even in environments where these conditions may fluctuate, reducing the need for extensive compensation or correction factors.

Thermal mass flow meters can be used across a broad range of gas flow applications. They are suitable for measuring the flow of various gases, including compressed air, natural gas, and specialty gases. This versatility makes them valuable in industries such as pharmaceuticals, petrochemicals, automotive, aerospace, and more.

Thermal mass flow meters typically have a low-pressure drop across the sensor, minimizing the impact on the system being measured.

As technology continues to advance, these instruments are likely to play an increasingly integral role in optimizing processes and improving overall efficiency.