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Teledyne Hastings Instruments Blog

FAQ Corner – What is turndown ratio?

Posted by Wayne Lewey on Mon, Jul 27, 2015 @ 04:03 PM

We are occasionally asked for the turndown ratios of our flow meters and flow controllers.  There are varying perceptions as to what this term actually means.

The turndown ratio of a Mass Flow Meter (MFM) or Mass Flow Controller (MFC) defines the usable range for which it can operate while maintaining its published accuracy.  It can be expressed using the following formula:

Turndown_ratio

Teledyne Hastings Flow Meter HFM-200-202A flow meter with a large turndown ratio will have a large operating range.  This can also be indicative of the flow meter’s cost.  For example, variable area flow meters (rotameters) typically have lower turndown ratios compared to thermal mass flow meters.

Most analog mass flow meters have an accuracy of ± 1% of Full Scale (FS) and have resolution better than 1%.  The usable range is from 1% to 100%.  They will have a turndown ratio of 100/1 or more commonly expressed as 100:1.  Digital flow meters will have an even greater turndown ratio due to their higher accuracy.

HFC-D-308Most analog mass flow controllers also have an accuracy of ± 1% FS.  However, they typically have an automatic valve shut circuit that closes the valve at flow rates below 2% of FS.  This is to ensure full valve closure in the event of a small zero offset.  The usable range is from 2% to 100%.  Since measurement is not possible below 2%, these will have a turndown ratio of 100/2 = 50/1 or 50:1.

 For more information on Turndown Ratio or our Flow Meters, please contact Wayne Lewey 

 

 

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Tags: Flow Meter

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

Be sure to visit our website for additional information on Teledyne Hastings Mass Flow Controllers and Mass Flow Meters

Tags: Flow Meter

Facts You Might Not Know about Teledyne Hastings Instruments

Posted by The Teledyne Hastings Team on Thu, May 14, 2015 @ 04:45 PM

Quality Teledyne Hastings ISO 9001 CertificationLast month, we passed our ISO 9001 surveillance audit.  It has been over twenty years since we first obtained ISO and we wanted to take a step back and review some significant accomplishments.  

Teledyne Hastings Instruments rich history and customer centric vision continues to support, influence and grow with those who depend on quality process control and automation.

That's why we wanted to take a moment and celebrate a milestone with our core clients and those considering a Teledyne Hastings Instruments Flow instrument or Vacuum Gauge for the first time.


2015_Infographic_ISO_20_Years_2

Teledyne Hastings Instruments' has been providing quality thermal mass flow instruments and vacuum meters and controllers for applications ranging from academic research to space exploration for over 70 years.  Let us work with you to find the best solution for your process.

OEM, custom applications, lead time crunch, just curious:   

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Tags: Teledyne Hastings Instruments, Flow Controller, Flow Meter, Vacuum gauge, vacuum controllers, ISO 9001 and Thermal Mass Flow, ISO 9001 and Vacuum Gauges

Desired Characteristics of a Thermal Mass Flow Sensor - Part 1 of 2

Posted by Will Harrison on Fri, Mar 20, 2015 @ 10:59 AM

ThermalMassFlowSensorCutawayThis is part 1 of a 2 part blog on Thermal Mass Flow Sensor.  We will describe the desired characteristics of a thermal mass sensor in Part 1 and Part 2 will discuss the operation of the 300 Series flow sensor (Patent #6,125,695) from Teledyne Hastings.

A thermal mass flow meter consists of the following:

  • Electronic Circuit Card

  • Flow Sensor

  • Bypass Shunt

  • Base

A cutaway is shown in the image on the right.

In a typical thermal mass meter, gas enters the flow meter via the upstream port which is attached to the process with a fitting (VCR, Swagelok…). Most of the gas will move through the bypass shunt; however, a certain fraction will flow through the thermal mass flow sensor. Note that the shunt is selected such that amount of gas moving through the flow sensor is approximately the same at full scale flow. The gas then exits the flow meter via the downstream port.

Ideally, the thermal mass flow sensor would exhibit the following characteristics: first, it would be linear. What we mean by linear is that the sensor’s electronic output should be directly proportional to the flow rate moving through the sensor throughout its range. Linearity of the flow sensor leads to the second desired characteristic: accuracy. An accurate flow sensor can give the users the benefit of better gas flow measurement, control, and understanding of their system parameters.

FlowSensorOutput

Before we move on with our desired characteristic list, we need to discuss a little about how linearity can factor into calibration. Typically, a thermal mass flow meter is calibrated in nitrogen (or in the case of very large flows, it may be calibrated in air). The output of the flow meter can then be scaled for use in other process gases. (In other words, the flow meter technician can calibrate a flow meter for use in a corrosive process gas like silane (SiH4) – without having to use silane). A linear flow sensor will retain its linear behavior as the gas is switched from the calibration gas (N2) to the process gas.

Our next desired characteristic is fast response. Ideally, the flow sensor would respond instantaneously to a change in the flow rate. Aside from the obvious benefit of instant real-time vision of the flow in a process, fast response becomes critical when the flow meter is coupled with a proportional control valve to create a thermal mass flow controller. Finally, we would like the thermal mass flow sensor to have a low pressure drop. A low differential pressure drop across the flow meter is ideal for leak detection and gas sampling applications.

Teledyne Hastings' Thermal Mass Flow Sensors are used worldwide.  For more information on on Best Practices for Mass Flow Controllers and Mass Flow Meters download our whitepaper.

Download Whitepaper

Be sure to visit our website for additional information on Teledyne Hastings Mass Flow Controllers and Mass Flow Meters

In our next blog, we will describe the sensor that is core to the Teledyne 300 Series of mass flow meters. We will also look at how the 300 Series thermal mass flow sensor addresses each of the desired characteristics described above.

 

 

Tags: Thermal Flow

Piezoresistive Pressure Sensors and the HPM-760S

Posted by Will Harrison on Thu, Nov 20, 2014 @ 10:09 AM

Piezoresistive Pressure Sensors - Direct Vacuum Gauges

In the vacuum world, gauges can be characterized as being either “Direct” or “Indirect”. Direct gauges are so-called because they directly measure the force imparted on some surface. And since P = F /A (pressure equals force per unit area), the gauge is directly measuring the pressure. Some examples of direct gauges would include: Bourdon gauges, capacitance manometers, piezo-resistance gauges (we’ll talk more about this one later in this blog).

Bourdon Gauge Teledyne Hastings Instruments Framed

                                                            Bourdon Gauge

 

Indirect gauges do not “directly” measure the force associated with the gas in the chamber. Rather, these gauges measure some property associated with the gas. For example, thermocouple vacuum gauge tubes measure the thermal conductivity of the gas which is a function of the pressure. As another example, ionization gauges measure the ionization rate of a gas which is proportional to the pressure over a several orders of magnitude. So, thermocouple gauges and ionization gauges can both be called Indirect Gauges.

Thermocouple_Guage_Tubes_Teledyne_Hastings_Instruments_framed                 Ionization Gauge IGE3000

    Thermocouple Gauge                                                       Ionization Gauge

 

One of the key features of a Direct Vacuum Gauge is that it does not matter what gas in the vacuum is being measured. In other words, if the user has 20 Torr of Argon, Helium, Methane… or Air, a Direct Gauge will read the same pressure. To say it another way, Direct Gauges are said to be Gas Composition Independent.

Teledyne Hastings provides a Direct Vacuum Gauge called the HPM-760S. (It is called the 760 because it will always provide very accurate results at atmospheric pressure.)  The HPM-760S utilizes a piezoresistive sensor. A cutaway drawing of this sensor is shown in the figure below.

 

In this cutaway, we can see the micro-machined sense die. This die contains a resistance bridge that is made up of piezo-resistors. In a piezoresistor, the resistance changes as force is applied. The resistance bridge sensor is itself in contact with silicone oil that transmits the force from the gas in the vacuum system to the sensor. And, one of the most important things to observe about this sensor is that the only wetted material actually exposed to the gas in the vacuum chamber is 316L Stainless Steel. So to summarize, the gas molecules in the vacuum system exert a force onto the stainless steel diaphragm which in turn imparts a force on the piezo-resistive sense via the silicone oil.

 

Cross Section of HPM-760 Sensor

One last thing to mention about our cutaway drawing: the sensor of the HPM-760S is referenced to vacuum. This type of arrangement gives ABSOLUTE readings. Other types of pressure sensors can be referenced to atmospheric pressure (GAUGE readings) or can be connected to another part of the process stream (DIFFERENTIAL) readings.

                 

The HPM-760S is a DIRECT, ABSOLUTE, vacuum gauge. It is an excellent gauge for use on systems that are evacuated using a diaphragm pump. These types of pumps typically operate in the region between a few Torr and atmosphere. And, as mentioned previously, the HPM-760s has only stainless steel exposed (wetted) to the gas in the vacuum chamber. In other words, any gas (including corrosives) which is compatible with stainless steel will be compatible with the HPM-760S.

 

HPM 760S Transducer Teledyne Hastings Instruments framed                                                          HPM-760S

The HPM-760S takes the output from the piezo-resistance bridge and amplifies it for the convenience of the user. At time of order entry, the user can select from four linear outputs.

 

760_Sensor_Output_Options-1

Two more quick notes about the analog output: First, selection of the 0-10 VDC version makes the conversion from voltage to pressure trivial. As a specific example, at 760 Torr, the voltage output is 7.60 Volt – SIMPLE.  Second, the 4-20 mA output is a good selection in industrial environments that might have lots of electrical noise/interface or where the pressure signal must be transmitted long distances  (>25 feet or 10 meter).

 

In addition to the linear outputs, the user can also select from several common vacuum system connections:

760_Sensor_end_fittings

 

 

 

 

 

 

 

The HPM-760s is very easy to use. See the image below. Two wires (Pins 3 & 4) are used to provide power to the HPM-760S. The two other wires (Pins 1 & 2) provide the linear output. So the HPM-760s can be used as a stand-alone vacuum gauge.

 


HPM 760S pin out Teledyne Hastings Instruments

 

In some cases, a user might like the convenience of having a readout preconfigured for the HPM-760S. The THCD-100 (shown below) can be quickly attached using the CB-760S-THCD cable. In this scenario, the user not only gets a power/display module, but the THCD-100 will also provide dual process control relays. The THCD-100 can be easily connected to a computer or PLC via RS232. And finally, by using the DisplayX software (free) for the THCD-100, the user can also easily collect and log data to a spreadsheet.

THCD-100_Teledyne_Hastings_Instruments

                THCD-100

  

 

 

  Download Tech Note  

 

 

This blog was prepared by Will (Iron Man) Harrison and Doug Baker. Will runs at least two marathons per year – this Fall, Will is going to run his first New York City Marathon.

 

Tags: Vacuum gauge, Sensor, vacuum instruments, pressure, vacuum pressure

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

New! Free Teledyne Hastings Mass Flow Converter APP

Posted by Doug Baker on Tue, Aug 05, 2014 @ 02:56 PM

Teledyne Hastings is proud to offer our Mass Flow Converter app. We have created a version for iPhone, iPad, and Droid. We have also created a web-based version that you can find at www.massflowconverter.com

In this blog article, we will discuss the motivation to build the app, how it works, and how it can be used.

The first question you might be asking is: Why do we need an app to convert from one set of mass flow units to another? For instance, if you want to convert from inches to centimeters, you would just multiply by 2.54. But, converting between mass flow units is not always that straight forward. So we have developed a tool that makes it easy.

We are going to look at some examples, but first let’s review what we mean by mass flow. When we think about mass flow, it can be helpful to think in terms of the flow of individual molecules. So while flow meters are often specified by units like sccm (standard cubic centimeters per minute) or scfm (standard cubic feet per minute), the mass flow rate is ultimately about the number of molecules (n) moving through a given cross sectional area per unit time (see figure below).

 

 Cross Section resized 600

 

 

 

So as our first example, let’s take a look at the conversion of 10,000 sccm (10,000 cm3/min) to a molecular flow rate. First, we need to ask, “How many molecules are in 10,000 sccm?” In the figure below, we show a container that is 10,000 cm3 in volume. Now, before we can calculate the number of gas molecules in a volume, we must know the pressure and temperature of the gas. We can use the ideal gas law:

n = (P * V) / R*T where n is the number of molecules, P is the pressure, V is the Volume, R is the Universal Gas Constant and T is the Temperature.

 

Framed Molecules per volume

Now we need to select some given pressure and temperature so that we can calculate the number of molecules – these are called the reference conditions or the STP (Standard Temperature and Pressure). In many cases, 0°C and 760 Torr are used for the STP. But this is not always the case. So it is always very important to specify the reference conditions (STP) any time you use a standardized mass flow unit like sccm, slm, scfh, etc (any mass flow unit that starts with “s” is going to need the reference conditions or STP specified). In our example, we are going to use STP of 0°C & 760 Torr.

OK, so here we go:     n = (1 atm) * (10,000 cc) / (82.053 cc * atm / K * mole) * (273 K)

Note that we have used a value of R in terms of pressure in Atmosphere (760 Torr = 1 atm), and Temperature in Kelvin (0°C = 273K). 

n = 0.45 mole

In other words, a flow rate of 10,000 sccm (0C, 760 Torr) is the same as a molecular flow rate of 0.45 Mole / minute.

OK that is the hard way. It’s much easier to use the mass flow converter app. In the example shown above, we would dial sccm on the left and Mole/Min on the right. Then to select the reference conditions, we use the menu in the center. See Fig. 3

 Framed screen shot mass flow converter app N2 resized 600

If you are like me, you will start to play with the App. And soon you will notice that the user can change the gas using the pull down menu at the top. But notice that in the case of our first example (converting from standardized mass flow units to molecular flow units), that the gas selection has no effect on the conversion.  This is because the standardized flow units (e.g. sccm, slm, scfh, etc.) are actually molar flow units based on reference conditions (STP) and the ideal gas law.

So, why do we allow the user to select gas? In the case of units like gm/sec, Kg/hr, or lb / min, we are going to need to know the gas so that we can calculate the mass. Let’s take a look at the case of converting from slm to grams/second. We will use as our same example of 10,000 slm (0°C & 760 Torr) and we will use methane (CH4) as our gas.

We showed earlier that 10,000 sccm is a molecular flow rate of 0.45 Mole / Min.  And since 1 slm = 1000 sccm, it is easy to see that 10,000 slm = 450 Mol/min. And since we know that our unit of choice (gm/sec) is in terms of seconds, let’s go ahead and convert our time units now:

10,000 slm = (450 Mole / Min) * (1 Min / 60 sec) = 7.5 Mole/ sec.

Now we need to know how much mass there is in a Mole of methane. Google is very nice for getting this number – just type, “Molecular weight of methane” and here is the result:

 

Framed mass flow converter app google screen shot resized 600 

 

By the way, Google will do this for almost all gases. So now we can finish our conversion and we get:

 

7.5 Mol / sec * (16.04 g/mol) = 120 g/sec

 


Framed mass flow converter app screen shot CH4 2 resized 600 

 

The mass flow converter app and website www.massflowconverter.com takes all the work out of these conversions and we hope that you will find this tool helpful. If you have any questions about mass flow meters and controllers, Application Engineers at Teledyne Hastings are always happy to help.

Tags: Teledyne Hastings Instruments, Flow Controller, mass flow conversion, Mass Flow Calculator, Mass Flow Range, Gas Flow Range, Mass Flow, Flow Meter, units conversion

FAQ Corner – Specifying range, pressures on Mass Flow Instruments

Posted by Wayne Lewey on Wed, May 29, 2013 @ 10:01 AM

We often see the label “One Size Fits All”.  This may be fine for some consumer goods.  However, it can be quite problematic when applied to items like shirts, gloves, or even golf clubs.  “One Size Fits All” also does not work for Mass Flow Controllers (MFC).  Not all applications are alike.  Forcing a “One Size Fits All” MFC into an unsuitable application can squander accuracy and induce valve failure.

Why do you need to specify the gas flow range on a MFC?  The Full Scale (FS) Range and Gas on a MFC directly correlates to the transmitted output (analog or digital) of the device.  In an analog device, the maximum output value (such as 5 vdc or 20 mA) will be equivalent to the FS value.  The accuracy of most MFCs is a function of this FS Range.  For analog devices, it is commonly ±1% of FS.  For digital devices, it is commonly published to be ±(0.5% of Reading + 0.2% FS).  Selecting the FS Range close to an application’s maximum flow rate optimizes accuracy for that specific application.  This is a good practice.  In addition, the gas must be specified.  Most MFCs use thermal based sensors.  These sensors actually measure the molecular flow rate rather than the mass flow rate.  Various gas molecules transfer heat differently, and thus the gas must be known.

Why do you need to specify Upstream Pressure and Downstream Pressure on a MFC?  Again, not all applications are the same.  A “One Size Fits All” MFC is typically not set up for applications at high pressure, low pressure, high differential pressure, or low differential pressure.  The definition of high and low will also fluctuate from one user to another.  Teledyne Hastings Instruments selects and tests MFC valve components (orifice, spring, etc.) that optimize valve stability for the exact application pressure conditions.When using a Teledyne Hastings Instruments MFC, you will always find the FS Range / Gas and the Upstream / Downstream Pressures listed on the serial number label.

Sample Calibration Sticker for MFC

 

Wayne Lewey was first exposed to mass flow controllers while an undergraduate at North Carolina State University (Chemical Engineering).  Today, Wayne is the International Sales Manager at Teledyne Hastings Instruments and can be reached at wlewey@teledyne.com.

Tags: Teledyne Hastings Instruments, Flow Controller, pressure, range, differential pressure, mass flow controller, Gas Flow Range, mass flow meter

FAQ Corner – Teledyne Hastings Instruments at Pittcon 2013

Posted by Brandon Hafer on Wed, Mar 13, 2013 @ 03:20 PM

It’s hard to believe that it is now March, which means that Pittcon 2013 is right around the corner. Teledyne Hastings Instruments will have Applications Engineers and representatives in attendance to answer all of your mass flow and vacuum instrumentation questions.

 

PITTCON 2013 LOGOPittcon is an annual conference on laboratory science that is organized by The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. Pittcon started as a small technical conference held in 1950. The first 18 conferences were held in Pittsburgh, Pennsylvania, but the conference has since grown. Locations now vary from year to year with this year’s conference being held at the Pennsylvania Convention Center in Philadelphia, Pennsylvania from March 17-21.

 

There have been many changes over the 60 plus years of the Pittsburgh Conference, and remains a worthwhile event to attend. Teledyne has had a presence at the event for the past 35 years. Included in the weeks events are thousands of exhibitors, numerous technical programs and lectures, and short courses. It provides the opportunity to meet and interact with scientist from across the country and around the world. Papers and articles are presented daily, illustrating the advancements in science in the past year. And finally, it allows for a single location to walk around and see over 17,000 companies and exhibitors with their products and technologies.

Teledyne Technologies Incorporated will have 4 companies in attendance at Pittcon this year. In addition to Teledyne Hastings Instruments, Teledyne Tekmar, Teledyne Leeman Labs, and Teledyne Judson will be exhibiting. Teledyne Tekmar is a leader in the design and manufacturing of analytical instrumentation including products for gas chromatography sample introduction, total organic carbon (TOC) and total nitrogen (TN) analyzers. Teledyne Leeman Labs is a producer of world-class instruments for elemental analysis including ICP spectrometers, atomic absorption spectrometers and mercury analyzers. Teledyne Judson is a leading designer and manufacturer of high performance infrared detectors and accessory products. The Teledyne family of companies will be located in booths 916 and 917, which are located near Entrance D to the Pennsylvania Convention Center. Teledyne employees will be giving presentations on a variety of topics while at Pittcon. If you would like more information on the schedule or the topics to be covered please contact us or stop by our booth and we can provide that information.

Teledyne Hastings Instruments has a great deal of experience with the analytical instrumentation industry. We are always interested in new applications even if they do not exactly fit into the standard product design for mass flow or vacuum instrumentation. We are very willing to examine possible custom designs to meet the requirements of your system. Some examples of previous custom applications include a variety of non-standard packages for both our mass flow and vacuum products, modified electronics, high pressure designs, and even custom designed flow and vacuum sensors.

 

We welcome your comments and your questions and look forward to seeing you at Pittcon 2013. Please stop by our booth and discuss your projects with either Vikki Jewel or Brandon Hafer. You can also email your questions to Victoria.Jewell@Teledyne.com or Brandon.Hafer@Teledyne.comand we’ll be happy to respond and work with you. 

Brandon Hafer is an Application Engineer with Teledyne Hastings Instruments. He was raised in Pottsville in Eastern Pennsylvania and is a fan of the Philadelphia Phillies and Philadelphia Eagles. He is looking forward to returning to the Philadelphia area for Pittcon 2013. If you would like to contact him, he can be reached at brandon.hafer@teledyne.com.

 

 

 

Tags: Teledyne Hastings Instruments, vacuum instruments, mass flow instruments

FAQ Corner – What is the Importance of STP Conditions on Mass Flow

Posted by Brandon Hafer on Thu, Mar 07, 2013 @ 03:19 PM

As I go through the day looking at various mass flow applications, I often notice that it is very easy for users to overlook one of the crucial items required for calculating mass flow. Looking at an application with its established requirements, we often jump right to determining “what flow rate is required?” However, it is important to remember that mass flow applications using volumetric units must reference a standard temperature and pressure. But why is this the case?

When examining liquid flow instruments, we know that liquids are incompressible and thus the amount of a substance present is determined by the volume being used. This leads to a simple calculation using density with the already determined volume to find the mass present in the volume or the volumetric flow.

GAs molecules @ STP Gases, however, ARE compressible and so the volume is only one factor in determining the amount of material being measured. If we look at the ideal gas law that you may remember from a chemistry class school (PV = nRT), we understand that temperature (T) and pressure (P) must also be considered in the equation. Otherwise it is impossible for us to know “how much” of the substance (n) there is in the space (V) or flowing through the system.

But given all of this information do we actually end up with the mass flow? The actual quantification of this “how much” calculation is expressed in moles (n), which is an extremely large number of molecules of a gas stated as Avogadro’s number, equal to 6.02x1023 (Don’t be scared by this value, though. A mole is a number, just like one dozen is 12, so one mole is 6.02x1023 molecules). Since the number of molecules of a gas and the mass are directly related for each gas type (i.e. molar mass), we are able to calculate the mass of the volume or volumetric flow based on the number of moles present. This is based on the assumption that the measured gas is pure and not contaminated with any other gases.

We’ll look at an example of the difference of STP conditions in a mass flow meter.  Teledyne Hastings Instruments assumes STP of 0°C and 760 Torr, but would prefer the customer to specify their STP conditions for the application. We will use the frequently referenced STP of 20°C and 760 Torr for the second part of this example. Suppose that we are looking to  measure 1 SLM (Standard Liter per Minute) of Nitrogen gas. As I’ve discussed earlier, the 1 SLM must be referenced to an STP value, so we will use our assumed conditions of 0°C and 760 Torr. If we were to change to the second set of conditions, the number of moles present in the flow (Molar Flow Rate) would change, and our mass flow rate would thus change (based on the direct relationship between mass and moles). Our initial mass flow rate of 1 SLM of Nitrogen at 0°C and 760 Torr would now be 1.074 SLM of Nitrogen at 20°C and 760 Torr.

Mass Flow Meter  Mass flow controllerAn important item to note is that the STP conditions are not actually present during the calibration of mass flow meters and mass flow controllers. Gas conditions are not brought to 0°C and 760 Torr prior to running calibration of equipment. The substance may not even be in gas phase at 0°C. The STP conditions are simply stated to define the standard volumetric flow rates of a substance IF it were an ideal gas at standard conditions.

This is also the reasoning for the addition of the “S” or “Standard” at the start of the stated volumetric flow rate (e.g. Standard Liters per Minute (SLM) or Standard Cubic Centimeters per Minute (SCCM)). We are stating the volumetric flow that would be present using standard conditions. So, using the information that we learned earlier, by stating the units in Standard Volumetric Flow Rate we are actually stating the Molar Flow Rate. This information changes based on the standards we are referencing and emphasizes the importance of stating the required STP conditions.

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Brandon Hafer is an Application Engineer with Teledyne Hastings Instruments. He completed his undergraduate degree studying meteorology at the Pennsylvania State University before serving as an officer in the United States Navy. He received his master’s degree in Systems Engineering from George Washington University and has been with Teledyne Hastings Instruments for two years. If you would like to contact him, he can be reached at brandon.hafer@teledyne.com.

Tags: Teledyne Hastings Instruments, Flow Controller, Flow Meter, STP, Thermal Flow, Standard Temperature and Pressure