Lecture 4: Flow & Velocity Measurements (2)libvolume2.xyz/biotechnology/semester3/... · 5 Lecture 4: Flow & Velocity Measurements (2) Biomedical Measurements | Bassel Tawfik Where

1 Lecture 4: Flow & Velocity Measurements (2)

Lecture 4: Flow & Velocity Measurements (2) Lecture Notes Systems & Biomedical Engineering Department Faculty of Engineering, Cairo

University

2008

Prof. Bassel Tawfik Biomedical Measurements

1/1/2008


Biomedical Measurements | Bassel Tawfik

Figure 3: Physical appearance of differential pressure transducers.

Lecture Outline

1. Other methods of flow measurement

2. Biomedical Applications

3. Topic of the Day: Biomimetic Sensors

1. Other Methods of Flow Measurements

1.1 Differential Pressure (The Pneumotachometer)

In a differential pressure transducer device, flow is calculated by measuring the pressure drop

across an obstruction inserted in the flow. The differential pressure flow meter is based on the

Bernoulli Equation, where the pressure drop and the further measured signal is a function of the

square flow speed (see figure next page and Bernoulli equation in Appendix B).

The calculation of fluid flow rate by reading the pressure loss across a

pipe restriction is perhaps the most commonly used flow

measurement technique in industrial applications (Figure 2-1). The

pressure drops generated by a wide variety of geometrical restrictions

have been well characterized over the years. In medical applications,

flow (denoted in the figures below as V') is derived from the pressure

difference across a small fixed resistance. This resistance is offered by

either a fine metal mesh (Lilly type – Figure 3) or arrays of capillaries

arranged in parallel (Fleisch type – Figure 4).

The pressure drop across the resistance is linearly proportional to flow

at relatively low flows, when the flow pattern is laminar. Turbulence makes the relationship

nonlinear. The tapered conic shape of the pneumotachometer’s ends helps achieve laminar

flow over a wide range of flows.

Adjacent figure is from the website of OMEGA corp. It shows the basic concept of using differential pressure to measure flow rate.



Figure 4: Lilly-type pneumotachometer

Figure 3: Fleisch type pneumotachometer

Figure 5: Pressure-Flow relationship of the differential pressure type flow meter



Figure 6: A primitive (portable) anesthesia machine with 2 rotameters, one for O2 and the other for N2O.

In an early design, the rotameter had slots which caused the float to spin for stabilizing and centering purposes. Because this float rotated, the term rotameter was coined.

Figure 7: Cross section of a rotameter.

1.2 Variable Area Flow meters (Rotameters)

The rotameter is the most widely used variable area

flow meter because of its low cost, simplicity, low

pressure drop, relatively wide range, and linear

output. It is constructed of a calibrated (transparent)

tube with a trapped bob (float) that moves freely

inside the tube. The tube is mounted vertically where

the upper end is slightly wider than the lower one

(tapered). This increasing area requires a larger

amount of fluid to force the float higher.

Rotameters can be used to manually set flow rates

by adjusting the valve opening while observing the

scale to establish the required process flow rate. The

fluid to be measured enters at the bottom of the

tube, passes upward around the float, and exits the

top. When no flow exists, the float rests at the bottom. When fluid enters, the metering float

begins to rise. In liquids, the float rises due to a combination of the buoyancy of the liquid and

the velocity head of the fluid. With gases, buoyancy is negligible, and the float responds mostly

to the velocity head.

Float

The float moves up and down in proportion to the fluid flow

rate and the annular area between the float and the tube wall.

As the float rises, the size of the annular opening increases. As

this area increases, the differential pressure across the float

decreases. The float reaches a stable position when the

upward force exerted by the flowing fluid equals the weight of

the float.

Every float position corresponds to a particular flow rate for a particular fluid's density and

viscosity. Hence, the flow rate can be determined by matching

the float position to a calibrated scale on the outside of the

rotameter. Many rotameters come with a built-in valve for

adjusting flow manually.

Several shapes and materials of float are available depending

on the application under consideration. Floats typically are

machined from glass, plastic, metal, or stainless steel for

corrosion resistance. They should have a sharp edge at the



Where q is the volumetric flow rate, Umax is the maximum velocity of fluid, Dt is the tube diameter, and Df is the float diameter.

point where the reading is observed on the tube-mounted scale. For improved reading accuracy,

a glass-tube rotameter should be installed at eye level.

Different Gases

A correlation rotameter has a scale from

which a reading is taken. This reading is

then compared to a correlation table for a

given gas or liquid to get the actual flow in

engineering units. Correlation charts are

readily available for nitrogen, oxygen,

hydrogen, helium, argon, and carbon

dioxide. While not nearly as convenient as

a direct reading device, a correlation meter is more accurate. This is because a direct-reading

device is accurate for only one specific gas or liquid at a particular temperature and pressure. A

correlation flow meter can be used with a wide variety of fluids and gases under various

conditions. In the same tube, different flow rates can be handled by using different floats.

Glass-tube rotameters are often used in applications where several streams of gases or liquids

are being metered at the same time or mixed in a manifold, or where a single fluid is being

exhausted through several channels.

It also is possible to operate a rotameter under vacuum. For applications requiring a wide

measurement range, a dual-ball rotameter can be used. This instrument has two ball floats: a

light ball (typically black) for indicating low flows and a heavy ball (usually white) for indicating

high flows. The black ball is read until it goes off scale, and then the white ball is read. One such

instrument has a black measuring range from 235-2,350 ml/min and a white to 5,000 ml/min.

Performance

Rotameters can be calibrated to an accuracy of 0.50 % AR over a 4:1 range, while the inaccuracy

of industrial rotameters is typically 1-2 % FS over a 10:1 range. Purge and bypass rotameter

errors are in the 5% range. If operating conditions remain unaltered, rotameters can be

repeatable to within 0.25 % of the actual flow rate.

Because the float is sensitive to changes in fluid density, a rotameter can be furnished with two

floats (one sensitive to density, the other to velocity) and used to approximate the mass flow

rate. The more closely the float density matches the fluid density, the greater the effect of a

fluid density change will be on the float position. Mass-flow rotameters work best with low

viscosity fluids such as raw sugar juice, gasoline, jet fuel, and light hydrocarbons.



Example

The XYZ Turbine System is a precision volumetric

instrument designed specifically for respirometry

volume-flow measurements. The Turbine System

consists of 3 modules: Electronic Module, Flow

Transducer body with cable and connector, and the

removable Turbine Cartridge. The Transducer body

comprises infrared optoelectronics and cable with

connector. It is not immersible. The operation of the

transducer is strictly digital. It transmits electrical pulses

and the pulses are counted as volume increments or

calculated as flow velocity. This is the principle for the

drift-free operation, long-term stability and consistent

accuracy.

Figure 8: Details of a turbine flow meter.

Rotameter accuracy is not affected by the upstream piping configuration. The meter also can be

installed directly after a pipe elbow without adverse effect on metering accuracy. Rotameters

are inherently self cleaning because, as the fluid flows between the tube wall and the float, it

produces a scouring action that tends to prevent the buildup of foreign matter. Nevertheless,

rotameters should be used only on clean fluids which do not coat the float or the tube. Liquids

with fibrous materials, abrasives, and large particles should also be avoided.

1.3 (Axial) Turbine Flow meters1

A turbine flow meter is a volumetric

flow metering device. It is a transducer

which senses the momentum of the

flowing stream. It consists of a rotor

and bearing assembly suspended on a

shaft, which is mounted to a support

device. This assembly is mounted

inside a housing with a known internal

diameter (Figure 1). As fluid passes

through the flow meter housing, the

rotor will spin at a rate proportional to

the volume of liquid passing through the housing.

The blades, which are usually flat but

may be slightly twisted, are inclined at

an angle to the incident flow velocity

and hence experience a torque that

drives the rotor. The rate of rotation,

which can be up to several tens of

thousands of rpm for smaller meters, is

detected by a pickup, usually a

magnetic type, and registration of each

rotor blade passing implies the passage

of a fixed volume of fluid. A modulated

carrier pick-off sensor may also be

used to detect the turn (passing) of

each rotor blade and generates a

frequency output. The frequency

output can be read directly via an electronic circuit. 1 Mostly used in aerospace, petroleum and water municipality industry.



SPECIFICATIONS (Simplified Version) ELECTRONIC VOLUMETRIC MODULE

FLOW RANGE: 0.05 - 16.50 L/sec (3.0 - 1000 L/min), VOLUME RANGE: Unlimited. RESPIRATION RATE: 0 - 150 Breaths/minute. ACCURACY: 3% (Typically 1%). STABILITY: Short and long term, 100%. WARM-UP TIME: None. BTPS* COMPENSATION: Compensates from 19 to 39 C in 2 C steps DIGITAL OUTPUT: 1: 100 pulses/liter nominal (100 us); BTPS* POWER REQUIREIMENT: +5 V, 5%, 120 mA with the Flow Transducer plugged in DIMENSIONS: 85 mm wide, 45 mm high, 135 mm deep; WEIGHT: 170 gram (6.0 oz)

Characteristics:

The flow sensing element is relatively compact and light weight

Works with both liquid and gas

Can be used bidirectionally

Response time: is on the order of 5 ms (Depends on size and mass of the rotor and the

fluid being measured)

Repeatability: up to ± 0.05% (Typically 0.1%)

Overall accuracy: up to ± 0.25% of reading over a wide turndown

Ruggedness of the design: Turbines are unaffected by vibration

Mostly invasive except when flow is measured at an end point (respired gas at mouth)

Wide operating temperature ranges: –270°C to 650°C (–450°F to 1200°F)



Figure 9

Velocity U

Current I

Sensor (thin wire)

Sensor dimensions:length ~1 mmdiameter ~5 micrometer

Wire supports (St.St. needles)

1.4 Hot Wire Anemometry2

1.4.1 Introduction A thermal (hot wire) anemometer uses a heated probe element that is inserted into an airstream. As air velocity increases, the temperature of the heated wire decreases. Air speed (velocity) can then be inferred either from the heating power necessary to maintain the probe at a constant temperature (constant temperature type) or the change in wire temperature (constant current type). A simplified sketch of the sensor is shown in figure 9. A hot wire type sensor must have two characteristics to make it a useful device:

(1) A high temperature coefficient of resistance (2) An electrical resistance such that it can be easily heated with

an electrical current Tungsten, platinum and a platinum-iridium alloys are commonly used materials with Tungsten

having the highest temperature coefficient of resistance, (0.004/C). The anemometer is capable of reading instantaneous values of velocity up to very high frequencies. Therefore it responds to and is capable of measuring the turbulent fluctuations in the flow field. (Most velocity measuring instruments, such as the Pitot Tube, respond very slowly effectively giving an average velocity over some longer time.)

2 An anemometer was first perceived as a device for measuring wind speed. The term is derived from the

Greek word, anemos, meaning wind.



Figure 12

Figure 11

Figure 10

1.4.2 Types A. Constant Temperature Anemometer (CTA) Here, the current through the wire is adjusted to maintain a constant film temperature. It works based on the fact that the probe’s resistance will be proportional to the temperature of the hot wire. The bridge circuit shown in Figure 10 below is set up by setting the adjustable resistor to the resistance you wish the probe and its leads to have during operation. (The other two legs of the bridge have identical resistance.) The servo (feedback) amplifier tries to keep the error voltage zero (meaning the resistances of the two lower legs of the bridge are equal). It will adjust the bridge voltage such that the current through the probe heats it to the temperature, which gives the selected resistance. When we put the probe in a flow, the air (or water) flowing over it will try to cool it. In order to maintain the temperature (resistance) constant, the bridge voltage will have to be increased. Thus, the faster the flow, the higher the voltage. A very simplified version of the relationship between the output voltage (shown in figure 10 as a dial symbol) and fluid velocity (for more accurate analysis, see Appendix C):

Eo2 = A +B vn (6)

Where Eo is the voltage across the wire, v is the velocity of the flow normal to the wire and A, B, and n are constants. We may assume n = 0.45 (or for classroom purposes, just a square root) this is common for hot-wire probes. “A” can be found by measuring the voltage on the hot wire with no flow, i.e. for v = 0, A = Eo

2.

Hot-wire anemometry can be used to measure and test respiratory

(pulmonary) function similar to turbine flow meters. The hot wires may be

installed within the same tapered

tube as shown in figure 11. In other

industrial applications and in

calibration devices, the flow meter

may look like that of figure 12.

Notice that temperature probes also

look like hot wire anemometer

http://www.omega.com/ppt/pptsc_lg.asp?ref=HHF42&Nav=



probes, so do not judge the function of a device just by its appearance!

B. Constant Current Anemometer (CCA)

In the constant current mode, nearly fixed electric current flows through the wire which is

exposed to the flow velocity. The wire attains an equilibrium temperature resulting from the

balance between internal heat generation due to electrical resistance (Joule heating) and the

convective heat loss from the wire to the moving fluid. The wire temperature must adjust itself

to changes in the convective losses until a new equilibrium temperature is obtained. Since the

convection coefficient is a function of the flow velocity, the equilibrium wire temperature is a

measure of the velocity. The wire temperature can be measured in terms of its electrical

resistance where the relationship between the resistance and temperature is known a priori.

1.4.3 Probe Design

The figure below shows a triaxial probe which is designed to measure the inclination of the flow

in 3D.


Typical Specifications

TAVM410 TAVM430

Specifications Airflow series - Hot Wire Anemometer Metric Imperial Metric Imperial

Velocity

Velocity range 0- 20.00 m/s 0.0 to 4000 fpm 0-30 m m/s 0.0 to 6000 fpm

Volume none none 0 - 2700 m3/sec 0 - 999,999 cfm Accuracy of velocity reading - greater of : ±5% of reading or ±0.025m/s ±5'/min ±3% of reading or

±0.015m/s ±3'/min

Resolution ±0.01 m/s 1 ft/min 1 ft/min ±0.01 m/s

Temperature

Range -10C° to +60°C 32 °F to +176°F -18C° to +93°C 0°F to +200°F Temperature Accuracy ±0.3°C ±1°F ±1 digit ±0.3°C ±0.5°F

Temperature Resolution 0.1°C 0.1°F 0.1°C 0.1°F

Probe

Probe dimensions extended 1016 mm 40.00" 1016 mm 40.00" Diameter at tip 7mm 0.28" 7mm 0.28" Diameter of telescope at base 13 mm 0.51 " 13 mm 0.51 "

Cable length 1 m 39.5" 1 m 39.5"

Data Logging none 12700 readings +100 IDs

Logging Interval 1 second to 1 hour

Battery 4 x AA Battery life ~ 15 hours with alkaline cells

Weight 270 g 9.6 oz 270 g 9.6 oz


1.5 Positive Displacement Flowmeters

1.5.1 How Positive Displacement Flowmeters Work

Positive displacement flowmeters repeatedly entrap fluid to measure its flow. It can be thought

of as repeatedly filling a bucket with fluid before dumping the contents downstream. The

number of times that the bucket is filled represents the flow. Many positive displacement

flowmeter geometries are available.

Entrapment is usually accomplished using rotating parts that form moving seals between each

other and/or the flowmeter body. In most designs, the rotating parts have tight tolerances so

these seals can prevent fluid from going through the flowmeter without being measured

(slippage). In some positive displacement flowmeter designs, bearings are used to support the

rotating parts. Rotation can be sensed mechanically or by detecting the movement of a rotating

part. When more fluid is flowing, the rotating parts turn proportionally faster. The electronic

transmitter processes the signal generated by the rotation to determine the flow of the fluid.

Some positive displacement flowmeters have mechanical registers that show the total flow on a

local display.



1.5.2 How to Use Positive Displacement Flowmeters (PDF)

Positive displacement flowmeters measure the volumetric flow of fluids in pipes, such as water,

hydrocarbons, cryogenic liquids, and chemicals. Some designs can measure gas flow. In liquid

service, increasing viscosity decreases slippage and increases the pressure drop across the

flowmeter. A large pressure drop across the flowmeter can prematurely wear and/or damage

bearings and/or seals. Note that flowmeter size may increase to reduce the pressure drop in

these applications.

One of the disadvantages of PDF’s is the possible damage of the sealing surfaces which results

in an increase in slippage and degradation of measurement accuracy. This usually happens in

abrasive or dirty fluids which in turn cause maintenance problems because of potential damage

to the sealing surfaces, damage to the bearings, and/or plugging of the flowmeter. A filter may

be required to remove dirt. Note that bearings usually do not fail suddenly; they slow down and

adversely affect accuracy before they stop working.

Be sure that gas bubbles are removed from liquid flow streams when using positive

displacement flowmeters. Flow measurement taken with bubbles will be higher than the true

liquid flow because the bubble volumes will be measured as if they were a volume of liquid. A

gas eliminator may be required to remove bubbles.

This flowmeter can be applied to clean, sanitary, and corrosive liquids, such as water and foods,

and some gases. Materials of construction are important because small amounts of corrosion or

abrasion can damage the sealing surfaces and adversely affect measurement accuracy. In

addition, consideration should be given to all wetted parts, including the body, rotating parts,

bearings and gaskets.

Many positive displacement flowmeters are used in municipal water districts to measure

residential water consumption. Corrosive liquid applications are commonly found in the

chemical industry processes, and in chemical feed systems used in most industries.

1.5.3 Application Cautions for Positive Displacement Flowmeters

Avoid using positive displacement flowmeters in dirty fluids unless the dirt can be effectively

removed upstream of the flowmeter. Operating these flowmeters in dirty fluids can cause

plugging and increase maintenance costs. Be careful when selecting bearings because the non-

lubricating nature of some fluids, impurities, and dirt can increase bearing wear and

maintenance costs.

Avoid liquids with gas bubbles unless the bubbles can be effectively removed. As viscosity

increases, be sure to ensure that the pressure drop across the flowmeter is acceptable. Make

http://www.flowmeters.com/ufm/index.cfm?task=glossary#volumetric_flow_measurement

http://www.flowmeters.com/ufm/index.cfm?task=glossary#hydrocarbons

http://www.flowmeters.com/ufm/index.cfm?task=glossary#cryogenic

http://www.flowmeters.com/ufm/index.cfm?task=glossary#viscosity

http://www.flowmeters.com/ufm/index.cfm?task=glossary#abrasive

http://www.flowmeters.com/ufm/index.cfm?task=glossary#sanitary

http://www.flowmeters.com/ufm/index.cfm?task=glossary#corrosive

http://www.flowmeters.com/ufm/index.cfm?task=glossary#materials_of_construction

http://www.flowmeters.com/ufm/index.cfm?task=glossary#materials_of_construction



sure that the viscosity of the operating fluid is similar to that of the calibrated fluid, because the

different amounts of slip exhibited by different fluids can cause measurement error.



Figure 1: Desktop spirometer. Notice some of the specs

of the system such as the LCD display screen, printout,

keypad to enter data, and type of data displayed

(figure 3). Notice also the noseclip.

Figure 3: Typical maximum flow-volume curve (loop).

2. Biomedical Applications

3.1 Respiratory System

A. Spirometry

Spirometry is the measurement of

volume and flow rate of gas breathed

in and/or out of the lungs under

maximal effort. Spirometers may be

handheld or PC-based. They are

mostly based on flow rate

measurements (figure 1) but

sometimes measure volumes directly

(figure 2).

Spirometry relies on the cooperation

of the subject, and hence is not

suitable for babies, subjects under

anesthesia or bed-ridden patients.

Figure 2: Direct volume measuring

spirometer.



B. Measurements of FRC

Spirometry can only obtain information about spontaneous breathing (volume, flow, and

pressure at mouth during rest, exercise, and maximal efforts). This is due to the fact that

spirometry measures volume deviations from a baseline (FRC = Lung volume at rest).

Consequently, spirometry cannot obtain information about absolute lung volume, namely, FRC

(Functional Residual Capacity) and RV (Residual Volume).

Measurement of absolute lung volume can be obtained by three techniques known as Nitrogen

washout, Helium dilution, and Body plethysmography. We shall describe these methods in

brief.

B.1 Nitrogen Washout

Nitrogen represents approximately 80% of the air in the lungs at any point of time3. Measuring

Nitrogen is useful in many medical, industrial and environmental applications such as

monitoring environmental regulatory compliance. Nitrogen is measured using gas analyzers

and the resulting values are displayed in particles per million (ppm). Other important gas

analyzers in the medical field are Oxygen and Carbon dioxide analyzers.

The method is based on the premise that if we can extract all the nitrogen in the lungs (from

which the word “washout” came) and calculate its volume, then this volume would be equal to

0.8 FRC. How would we collect all the N2 in the lungs? The answer is by continually inspiring air

that has no N2, or simply pure O2, while directing expired gas to a collection chamber. Nitrogen

concentration in the expired gas would then be measured until it displays no change in

concentration. This indicates that the lungs are completely depleted of N2. Finally,

FRC = [1/0.8] [concentration of N2 in chamber] x [Total volume of gas expired]

There are several sources of error in this measurement, namely:

(1) Gas trapped in dead space of instrument

(2) Gas trapped in alveoli due to emphysema and other pulmonary diseases, i.e. poorly

ventilated or non-ventilated areas will not be included as part of FRC

(3) Existence of gas in chamber prior to beginning of experiment

(4) Need for adjustment to BTPS (Body Temperature & Saturated Pressure)

3 Assuming very little or no trapped air in alveoli which would contain more CO2 and hence less N2.



B.2 Helium Dilution (Closed Circuit)

Poorly ventilated or non-ventilated areas will not be included as part of FRC when measured

with this technique.

B.3 Body Plethysmography

Assuming that the change in volume (V) = 71 ml, and that the change in lung gas pressure (P) =

20 mmHg, and that Ps = 760 mmHg, the calculation proceeds as follows:

PV P P V V ( )( )

Multiplying out

PV PV P V V P P V

Adding out PV’s, rearranging, and factoring

VV P P

P

( )

Since P is quite small relative to P (20 mmHg versus 713 mmHg), then

VV

PP

( )

V 71

2 531 ml (713 mmHg)

20 mmHg ml = Volume at FRC,



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Figure 1: A photo of a urodynamic system showing the

control/display module and the catheter.

3.2 Lab Safety: Fume Hoods (Biosafety Cabinets)

Laboratory fume hoods are designed to protect laboratory personnel by preventing contaminants such as chemical vapors, dusts, mists and fumes from escaping into the laboratory environment. Fume hoods also provide lab personnel with a physical barrier to chemicals and their reactions. Fume hoods are evaluated each year to verify their proper operation. Where possible, face velocity will be set at 100 feet per minute (fpm) with sash at 18". The method most commonly used to verify this velocity is anemometry.

3.3 Urodynamics

Urodynamic investigations are the only way to evaluate bladder and urethral functions. Urodynamic investigations allow characterization of the pathophysiological aspects of the different symptoms, give some elements to determine accurately the prognosis and help for the choice of the therapeutic strategy.

Measurement of the urinary flow rate confirms the presence of a bladder outlet obstruction. Urine flow rate is measured with a flow-meter that measures a quantity of fluid passed per unit time, expressed in milliliters per second.

Uroflow depends on detrusor contractility and urethra-sphincter resistance. The voided volume should be more than 150ml. Patients are instructed to void normally, as in usual conditions, with a comfortably full bladder. Measurement of residual urine volume (by means of ultrasound or catheterization) is necessary to interpret the uroflowmetry results. The precise shape of the flow curve is decided by detrusor contractility, the presence of any abdominal straining and by the bladder outlet.

Sketch showing one type of fume hoods



Different parameters are studied. Flow rate (ml/s) is defined as the volume of fluid expelled via

the urethra per unit time. Voided volume is the total volume expelled via the urethra. Maximum

flow rate is the maximum measured value of the flow rate after correction for artifacts; it must

be greater than 15ml/s. Voiding time is total duration of micturition and includes interruptions.

Flow time is the time over which a measurable flow actually occurs. Average flow rate is voided

volume divided by flow time. A normal flow curve is a smooth curve without any rapid changes

in amplitude. A decreased detrusor power and/or a constant increased urethral pressure

determine a lower flow rate and a smooth, flat flow curve. A constrictive obstruction (urethral

stricture) results in a plateau-like flow curve. A compressive obstruction (cystocele) shows a

flattened asymmetric flow curve. Rapid changes in flow rate may have several causes:

sphincter/pelvic floor contraction or relaxation (detrusor sphincter dyssynergia), voluntary flow

interruption, abdominal straining and artifacts (movement of the stream in the collecting

device, patient movements).

Cystometry is the method used to measure the pressure-volume relationships of the bladder.

Classically, the intravesical (total bladder) pressure is measured while the bladder is filled, but

this simple technique is not accurate because intravesical pressure is not representative in all

the cases of true detrusor pressure.

Reference: Elemental Healthcare (UK)



Figure D-1: Principle of an Acoustic Vibrator. The vibrating titanium tip of the distal end of the handpiece provides fluid pressure waves forcing existing intra- and extra-cellular cavities to grow and collapse. This sudden collapse at supersonic speeds leads to tissue cavitation. Vibration is initiated by a transducer that contracts and expands. On top of the transducer a titanium tip is mounted that is designed specially to function as an amplifier for the amplitude of the transducer. Magnifications up to ten times the amplitude are possible. The largest possible amplitude is preferred. A large amplitude can be achieved more easily by lower frequencies. Twenty-three kHz is more or less the lower limit to ensure that we are well above the audible frequency. Frequencies are typically 19 to 40 kHz, with maximum amplitudes 180 to 350 kHz.

3.4 CUSA4

CUSA® consists of a hollow

titanium tip that vibrates along

its longitudinal axis at 23 kHz.

When the tip of the instrument

is brought in contact with tissue,

mechanical energy is

transferred, creating high- and

low-pressure areas. When the

pressure is below the vapor

pressure of tissue fluid, vapor-

filled vacuoles form within the

cells. These vacuoles expand

and collapse as pressure rises

and falls with each cycle,

generating forces that fragment

the cells.

Tissue damage is confined to an

area of about 25 to 50µm next

to the tip, with minimal thermal

injury and protein denaturation.

A greater amount of tissue

damage results from the use of

a scalpel or laser. With

electrosurgical manipulation,

the extent of tissue damage exceeds 1,000 to 4,000 mm.

Another potential advantage of the CUSA® system is the selectivity of its dissection, a

consequence of the fact that the rate of cavitational activity is proportionate to the water

content of the cells, i.e., soft, fleshy tissues with high-water content are fragmented readily.

Therefore, different tissues fragment at different rates leading to the possibility of dissection

without affecting blood vessels. Because of these advantages, the CUSA® has been utilized for

dissection of water-dense collagen and elastin-rich structures, including ureters and nerves.

4 Surgical Technology International: Website at: www.ump.com/articles/cusa/CUSA.htm

http://www.ump.com/articles/cusa/CUSA.htm


Appendix (A)

The Pneumotachometer5

Specifications 730944 730945 730946 730947 730948 730949 730950 730951 730952 730963

Connection Diameter Metric

7 mm 7 mm 7 mm 10 mm 11 mm 19 mm 30 mm 45 mm 60 mm NA

Dead Space Volume 0.1 ml 0.8 ml 0.9 ml 2 ml 4 ml 14 ml 35 ml 80 ml 172 ml 460 ml

Differential Pressure (mmH2O)

6.25 mmH2O

6.25 mmH2O

6.25 mmH2O

6.25 mmH2O

6.25 mmH2O

6.25 mmH2O 6.25

mmH2O 6.25

mmH2O 6.25

mmH2O 6.25

mmH2O

Inner Diameter Metric 1.35 mm 6 mm 6 mm 9 mm 10 mm 18 mm 28 mm 43 mm 58 mm 78 mm

Length Metric 75 mm 75 mm 75 mm 75 mm 60 mm 60 mm 60 mm 60 mm 70 mm 100 mm

Maximum Flow Rate (ml/sec)

12 ml/sec 20 ml/sec 60 ml/sec 150

ml/sec 350

ml/sec 1200 ml/sec 3000 ml/sec

8000 ml/sec

14000 ml/sec

25000 ml/sec

Nominal Flow Rate (ml/sec)

9 ml/sec 15 ml/sec 40 ml/sec 100

ml/sec 250

ml/sec 1000 ml/sec 2500 ml/sec

6500 ml/sec

11000 ml/sec

21000 ml/sec

Nominal Sensitivity (ml/sec/mmH2O)

1.4 2.08 6.4 10.56 52.8 160 320 800 1600 3200

Simple Calirations (pressure = flow)

6 mmH2O = 6

ml/sec, 10

mmH2O = 10

ml/sec

1 mmH2O = 2

ml/sec, 5 mmH2O

= 10 ml/sec,

10 mmH2O

= 20 ml/sec

1 mmH2O = 6.4

ml/sec, 5 mmH2O

= 32 ml/sec,

10 mmH2O

= 64 ml/sec

1 mmH2O = 1.12

ml/sec, 5 mmH2O = 5.61 ml/sec,

10 mmH2O

= 7.9 ml/sec

1 mmH2O = 52.8

ml/sec, 5 mmH2O

= 264 ml/sec,

10 mmH2O

= 528 ml/sec

1 mmH2O = 140 ml/sec, 5 mmH2O = 700 ml/sec, 10 mmH2O

= 1327 ml/sec

1 mmH2O = 321 ml/sec, 5 mmH2O = 605 ml/sec, 10 mmH2O

= 3076 ml/sec

1 mmH2O = 800

ml/sec, 5 mmH2O = 4000 ml/sec,

10 mmH2O = 8000 ml/sec

1 mmH2O = 1400

ml/sec, 5 mmH2O = 7000 ml/sec,

10 mmH2O = 14000

ml/sec

NA

Species Mouse

(50 gr)

Small Guinea

Pig or rat (170 gr)

Guinea Pig or Rat

(350 gr)

Small animal,

Cat (750 gr)

Cat or Dog (5.5

kg)

Dog or Pig (27 kg)

Large Animal

Large Animal

Large Animal

Large Animal

Weight Metric 140 g 140 g 140 g 140 g 140 g 140 g 150 g 250 g 400 g 650 g

5 From the datasheet of Harvard Apparatus: http://www.harvardapparatus.com/webapp/wcs/stores/servlet/product_11051_10001_41166_-

1_HAI_ProductDetail_37841__N

http://www.harvardapparatus.com/webapp/wcs/stores/servlet/product_11051_10001_41166_-1_HAI_ProductDetail_37841__N

http://www.harvardapparatus.com/webapp/wcs/stores/servlet/product_11051_10001_41166_-1_HAI_ProductDetail_37841__N


Appendix (B)

The Bernoulli Equations6

A special form of the Euler’s equation derived along a fluid flow streamline is often called the

Bernoulli Equation

6 Source: www.engineeringtoolbox.com

http://www.engineeringtoolbox.com/fluid-mechanics-equations-d_204.html

http://www.engineeringtoolbox.com/



For steady state incompressible flow the Euler equation becomes (1). If we integrate (1) along

the streamline it becomes (2). (2) can further be modified to (3) by dividing by gravity.

Head of Flow

Equation (3) is often referred to the head because all elements has the unit of length.

Dynamic Pressure

(2) and (3) are two forms of the Bernoulli Equation for steady state incompressible flow. If we

assume that the gravitational body force is negligible, (3) can be written as (4). Both elements in

the equation have the unit of pressure and it's common to refer the flow velocity component as

the dynamic pressure of the fluid flow (5).

Since energy is conserved along the streamline, (4) can be expressed as (6). Using the equation

we see that increasing the velocity of the flow will reduce the pressure, decreasing the velocity

will increase the pressure.

This phenomena can be observed in a venturi meter where the pressure is reduced in the

constriction area and regained after. It can also be observed in a pitot tube where the

stagnation pressure is measured. The stagnation pressure is where the velocity component is

zero.

Example - Bernoulli Equation and Flow from a Tank through a small Orifice

Liquid flows from a tank through a orifice close to the bottom. The Bernoulli equation can be

adapted to a streamline from the surface (1) to the orifice (2) as (e1):

http://www.engineeringtoolbox.com/fluid-mechanics-equations-d_204.html



Since (1) and (2)'s heights from a common reference is related as (e2), and the equation of

continuity can be expressed as (e3), it's possible to transform (e1) to (e4).

Vented tank

A special case of interest for equation (e4) is when the orifice area is much lesser than the

surface area and when the pressure inside and outside the tank is the same - when the tank has

an open surface or "vented" to the atmosphere. At this situation the (e4) can be transformed to

(e5).

"The velocity out from the tank is equal to speed of a freely body falling the distance h." - also

known as Torricelli's Theorem.

Example - outlet velocity from a vented tank

The outlet velocity on a tank were

h = 10 m

can be calculated as

V2 = [2 x 9.81 x 10]1/2 = 14 m/s

http://www.engineeringtoolbox.com/equation-continuity-d_180.html

http://www.engineeringtoolbox.com/equation-continuity-d_180.html



Pressurized Tank

If the tanks is pressurized so that product of gravity and height (g h) is much lesser than the

pressure difference divided by the density, (e4) can be transformed to (e6).

The velocity out from the tank depends mostly on the pressure difference.

Example - outlet velocity from a pressurized tank

The outlet velocity of a pressurized tank where

p1 = 0.2 MN/m2, p2 = 0.1 MN/m2 A2/A1 = 0.01, h = 10 m

can be calculated as

V2 = [(2/(1-(0.01)2) ( (0.2 - 0.1)x106 /1x103 + 9.81 x 10)]1/2 = 19.9 m/s

Coefficient of Discharge - Friction Coefficient

Due to friction the real velocity will be somewhat lower than this theoretic examples. If we

introduce a friction coefficient c (coefficient of discharge), (e5) can be expressed as (e5b).

The coefficient of discharge can be determined experimentally. For a sharp edged opening it

may be as low as 0.6. For smooth orifices it may bee between 0.95 and 1.



Appendix (C)

Hot-Wire Anemometer Theory

Consider a wire that's immersed in a fluid flow. Assume that the wire, heated by an electrical current input, is in thermal equilibrium with its environment. The electrical power input is equal to the power lost to convective heat transfer,

Where I is the input current, Rw is the resistance of the wire, Tw and Tf are the temperatures of the wire and fluid respectively, Aw is the projected wire surface area, and h is the heat transfer coefficient of the wire. The wire resistance Rw is also a function of temperature according to,

Where a is the thermal coefficient of resistance and RRef is the resistance at the reference temperature TRef. The heat transfer coefficient h is a function of fluid velocity vf according to King's law,

Where a, b, and c are coefficients obtained from calibration (c ~ 0.5). Combining the above three equations allows us to eliminate the heat transfer coefficient h,

Continuing, we can solve for the fluid velocity,



Two types of thermal (hot-wire) anemometers are commonly used: constant- temperature and constant-current.

The constant-temperature anemometers are more widely used than constant-current anemometers due to their reduced sensitivity to flow variations. Noting that the wire must be heated up high enough (above the fluid temperature) to be effective, if the flow were to suddenly slow down, the wire might burn out in a constant-current anemometer. Conversely, if the flow were to suddenly speed up, the wire may be cooled completely resulting in a constant-current unit being unable to register quality data.

Constant-Temperature Hot-Wire Anemometers

For a hot-wire anemometer powered by an adjustable current to maintain a constant

temperature, Tw and Rw are constants. The fluid velocity is a function of input current and flow

temperature,

Furthermore, the temperature of the flow Tf can be measured. The fluid velocity is then reduced to a function of input current only.

Constant-Current Hot-Wire Anemometers

For a hot-wire anemometer powered by a constant current I, the velocity of flow is a function of the temperatures of the wire and the fluid,

If the flow temperature is measured independently, the fluid velocity can be reduced to a

function of wire temperature Tw alone. In turn, the wire temperature is related to the measured

wire resistance Rw. Therefore, the fluid velocity can be related to the wire resistance.

http://ww.efunda.com/DesignStandards/sensors/hot_wires/hot_wires_theory.cfm#temperature

http://ww.efunda.com/DesignStandards/sensors/hot_wires/hot_wires_theory.cfm#current



Appendix (D)

ATPS, ATP, BTPS, STPD

The volume of a number (n) of gas molecules depends on the thermodynamic temperature (T)

and the ambient pressure (P). The following relationship holds for dry gas:

V = n·R·T/P

Where R = gas constant, and T is expressed in Kelvin (K = 273.2 + ºC). Air and expired gas are

made up of gas molecules and water vapor. In a gas mixture saturated with water vapor and in

contact with water (such as occurs in the lung) the number of water molecules in the gas phase

varies with temperature and pressure. As the number of molecules is not constant, the above

gas law should be applied to dry gas. This also holds outside the lung when gas saturated with

water vapor is compressed or cools down.

As gas volumes vary with temperature and pressure, the conditions during which they are

measured must be recorded. To that end volume displacement spirometers need to be

equipped with a thermometer; if meters employ other measuring principles the manufacturer

should state clearly how corrections need be performed as the composition of the gas and gas

viscosity may then come into play.

BTPS In respiratory physiology lung volumes and flows are standardized to barometric pressure at sea level, body temperature, saturated with water vapor: body temperature and pressure, saturated.

ATPS Measured at ambient temperature, pressure, saturated with water vapor (e.g. expired gas, which has cooled down): ambient temperature and pressure, saturated.

ATP Like ATPS, but not saturated with water vapor (e.g. room air).

STPD Oxygen consumption and carbon dioxide delivery are standardized to standard temperature (0 ºC), barometric pressure at sea level (101.3 kPa) and dry gas: standard temperature and pressure, dry.

Conversion from ATPS to BTPS conditions

Temp.

ºC

Corr.

factor

Temp.

ºC

Corr.

factor

Temp.

ºC

Corr.

factor

Temp.

ºC

Corr.

factor

16 1.123 21 1.097 26 1.069 31 1.039

17 1.118 22 1.091 27 1.063 32 1.033

18 1.113 23 1.086 28 1.057 33 1.026

19 1.107 24 1.080 29 1.051 34 1.020

20 1.102 25 1.074 30 1.045 35 1.013



Appendix (D)

Oxygen Analyzer Theory of Operation



Topic of the Day: Biomimetic Sensors

Definition

Biomimicry (from bios, meaning life, and mimesis, meaning to imitate) is a relatively new science

that studies nature, its models, systems, processes and elements and then imitates or takes

creative inspiration from them to solve human problems sustainably. (Wikipedia)

Physiological Sensors

In general, sensors provide us with a quantified and objective scale to evaluate things. This

helps us determine their properties (e.g. temperature, force, weight, etc.).

Biomimetic Sensors

Some of the human sensors (senses) have been supplemented or enhanced by external man-

made sensors. These are the senses of sight, hearing, and touch. For instance, sight can be

enhanced (make minute things appear larger, far objects closer), extended (unseen objects seen

as in IR sensing), or replaced (still in its primitive form where the optic nerve is directly fed with

signals from imaging devices). Sound can also be amplified and processed to improve hearing.

But smell and taste have always been challenging to replicate or enhance. There is no need to

stress the importance of these two senses to human life.

Today industries such as: aircraft, automobile, sensor, chemical and pharmaceutical makers are

investigating biomimetic processes for several reasons such as: superior performance, low cost

raw materials, recyclability and mass production compatibility.



(1) DARPA (Defense Advanced Research Projects Agency - USA)

1.1 Flying Robotic Insects

DARPA’s latest call for proposals merited an interesting article in the Toronto Star. The advanced projects agency has requested labs to submit research plans that will lead to:

“.. the controlled arrival of an insect within five meters of a specified target located 100 meters away. It must then remain stationary indefinitely, unless otherwise instructed … to transmit data to sensors providing information about the local environment.”

The preferred methodology is to implant computational units in the larvae and allow them to integrate with the nervous system through pupation; a high goal indeed and one that is so far from any proven science that it certainly qualifies as ‘blue sky’ research. Last year DARPA gave out 3.1 billion for equally outside the box, high concept research.

1.2 Sharks on demand (http://technology.newscientist.com/article/mg18925416.300.html)

The Defense Advanced Research Projects Agency (DARPA) has been funding several labs interested in basic sensory biology. Their goal is to define a system that will allow remote control of a free swimming shark. The project has been under way for two years now with the major focus on the olfactory and the electrosensory systems. A recent meeting of the research group held in Hawaii has been reported in the New Scientist. Jelle Atema, better known for working on lobsters, has successfully implanted an electrode in each olfactory tract that causes a shark to veer one way or another. Tim Tricas is attempting similar things with the electrosensory system but is not yet able to build the interface with the shark. There are apparently trials scheduled for the Atema system to be held in open ocean off Florida.

(2) NSF (National Science Foundation – USA)

The National Science Foundation has a CAREER award that rewards particularly promising young

scientists with a 5 year (rather than the standard three year) research grant. The University of

Delaware’s Xinyan Deng has won one to study robotic flies.

http://technology.newscientist.com/article/mg18925416.300.html

http://images.google.com/imgres?imgurl=http://www.elasmodiver.com/Sharkive images/Blue shark 041.jpg&imgrefurl=http://www.elasmodiver.com/Sharkive Blue shark.htm&h=399&w=601&sz=42&tbnid=RYxFrUi700uY0M:&tbnh=88&tbnw=133&hl=en&start=7&prev=/images?q=blue+shark&svnum=10&hl=en&lr=&safe=off&client=firefox-a&rls=org.mozilla:en-US:official&sa=N



“…one of the goals of the research is to study the flight

attributes observed in insects and to investigate the underlying

principles that result in flight stability and also lead to

differences in performance in order to develop a methodology

and guidelines for designing flapping-wing microaerial vehicles.”

Beside mathematical modeling and theoretical studies, Deng hopes to design and fabricate

workable flapping-wing microaerial vehicles, or miniature flying robots, that are capable of

stable and maneuverable flight with biomimetic sensors.



Smelly frogs don't get insect bites

Some Australian frogs create their own insect repellent,

some resembling rotten meat and others roasted cashew

nuts or thyme leaves, researchers find.

The research team, which includes Associate Professor Mike

Tyler of the University of Adelaide and entomologist Dr Craig

Williams from James Cook University, publishes its findings

online in the journal Biology Letters.

Frogs produce a number of chemicals in their skin, including

hallucinogens, glues and antimicrobials, to ward off infection

and stop other animals from trying to eat them.

"We wanted to test Professor Tyler's [belief] that they

should also produce an insect repellent," says Williams.

The research team studied five species of Australian frogs,

including the Australian green tree frog.

Using massage and acupuncture techniques, they stimulated

the muscles beneath the frogs' skins to produce secretions.

"What we found was that frogs produce a variety of

chemicals in their skin and these ooze out of the pores of

their skin when they are stressed," says Williams.

The secretions, some of which repel mosquitos, have different smells depending on a number of

factors such as what the frog eats.

Jacquie van Santen

ABC Science Online

Wednesday, 22 February 2006

Frogs produce a range of

chemicals in their skins, including

ones that smell like cashew nuts.

Now scientists say some of these

chemicals repel insects (Image:

Michael Tyler)

http://www.adelaide.edu.au/

http://www.jcu.edu.au/

http://www.journals.royalsoc.ac.uk/link.asp?id=110824



"The frogs produce hundreds of chemicals and one frog's smell might be made up of six or seven

different chemicals, so they all smell quite different," Williams says.

"The chemicals evaporate very quickly from the skin and it's the volatile smell that repels [the

mosquitos]."

A new mosquito repellent?

The team found that skin secretions from an Australian green tree frog, for example, protected a

mouse from mosquitos when the secretion was applied.

The researchers say this is the first time a vertebrate has been found to have its own in-built

mosquito repellent.

But the frog secretion was not as repellent as DEET, diethyl-m-toluamide, the ingredient in most

commercial mosquito sprays.

Williams doesn't believe that a new brand of natural insect repellent will result from the

research.

"The smell is just not very good ... some smell of rotting flesh, some of nuts, some of thyme

leaves."

Last year the frog-sniffing research team won an Ig Nobel prize for its work on skin secretions.

The prizes honour "achievements that first make people laugh, and then make them think".

At the time, the researchers talked about frog smells that reminded them of Bombay curry and

cut grass.

http://www.improb.com/ig/



Glossary of Terms

Abrasive

Fluids are termed abrasive when they have a tendency to mechanically attack metals and parts made from

other materials of construction.

Bernoulli's Equation

Bernoulli's equation describes the conservation of hydraulic energy across a constriction in a pipe. It states

that the sum of the static energy (pressure head), kinetic energy (velocity head), and potential energy

(elevation head) upstream and downstream of the constriction are equal.

Coanda Effect

Coanda Effect flowmeters channel the flow stream in the flowmeter so as to utilize the phenomenon that

causes a fluid to attach itself to a surface. Feedback passages are used to alternately attach the fluid to

each surface. Oscillating flows through the feedback passages can be related to the flow rate.

Conductivity

The electrical conductivity of a liquid is a measure of the ability of the liquid to conduct electricity (mS/cm).

Note that water with few impurities (such as de-ionized water) is not very conductive, whereas water with

impurities can be highly conductive.

Corrosive

Fluids are termed corrosive when they have a tendency to chemically attack metals and parts made from

other materials of construction.

Cryogenic

Fluids are termed cryogenic when they operate at low temperatures, typically below approximately -75°C.

Examples of these fluids include liquefied gases, such as oxygen and nitrogen.

Custody Transfer

Flowmeters applied to custody transfer are used to buy and sell fluids, such as the measurement of natural

gas between pipeline companies.

Density

The density of a fluid is its mass per unit volume (lb/ft3; kg/m3; g/cc). Specific gravity is a dimensionless

number that represents the density of the liquid relative to water.

Doppler Effect

The Doppler effect is a phenomenon related to how sound is perceived from objects in motion, such as the

horn of a moving car having a higher pitch moving towards a listener than it does when moving away.

Flow Nozzle

A flow nozzle is a constriction consisting of a contoured plate that forms a hole for the flow stream that is

sandwiched in the pipe between two flanges.

Hydrocarbons

Hydrocarbons is a general class of chemicals that contain hydrogen and carbon, such as natural gas, fuel oil

and gasoline. They are often flammable.



Industrial Gases

Industrial gases generally refers to pure gases that are commonly used industry, such as oxygen, nitrogen,

argon, and helium.

Inferential Flow Measurement

Inferential flowmeters do not measure volume, velocity or mass, but rather measure flow by inferring its

value from other measured parameters. Examples of flowmeter technologies that measure inferentially

include differential pressure, target and variable area flowmeters.

Laminar Flow Element

A laminar flow element is a constriction consisting of a tube bundle or parallel plates used to measure flows

with low Reynolds numbers. The differential pressure across this flowmeter is linear with flow.

Low-Loss Flow Tube

A low-loss flow tube is a constriction that is similar to a Venturi-tube, but with shorter inlet and outlet

sections.

Mass Flow Measurement

Mass flowmeters utilize techniques that measure the mass flow of the flowing stream. Examples of

flowmeter technologies that measure mass flow include Coriolis mass and thermal flowmeters.

Materials of Construction

Materials of construction are the materials from which the parts of the equipment are fabricated. Parts that

are exposed to the operating fluid are termed "wetted" parts.

Orifice Plate

An orifice plate is a constriction consisting of a flat plate with a hole for the flow stream that is sandwiched in

the pipe between two flanges.

Reynolds Number

Reynolds number is a dimensionless number that is used to describe the flowing characteristics of the fluid.

Operating a flowmeter outside of its Reynolds number constraint can degrade accuracy and make some

flowmeters turn off.

RD = 3160 · Flow gpm · Specific Gravity / (Viscosity cP · Diameter inch)

Sanitary

Sanitary piping systems and components are used where cleanliness is important, such as in the food and

beverage, pharmaceutical and chemical industries.

Segmental Wedge

A segmental wedge is a constriction consisting of a hill-like structure in the flow stream. It is often used for

fluids that contain some solids or that are mildly abrasive.

http://www.flowmeters.com/ufm/index.cfm?task=differential_pressure

http://www.flowmeters.com/ufm/index.cfm?task=target

http://www.flowmeters.com/ufm/index.cfm?task=variable_area

http://www.flowmeters.com/ufm/index.cfm?task=coriolis

http://www.flowmeters.com/ufm/index.cfm?task=thermal



Slurry

Slurries contain both liquid and solids, and are often used as a means to transport the solids.

V-cone

A V-cone is a constriction consisting of a cone suspended in the flow stream. It can be used in locations

where little space for upstream and downstream piping is available.

Velocity Flow Measurement

Velocity flowmeters utilize techniques that measure the velocity of the flowing stream to determine the

volumetric flow. Examples of flowmeter technologies that measure velocity include magnetic, turbine,

ultrasonic, and vortex shedding and fluidic flowmeters.

Venturi Tube

A Venturi tube is a constriction consisting of a streamlined reduction and expansion of the piping containing

an inlet section, throat, and outlet section.

Viscosity

The viscosity of a fluid is the ability of the fluid to flow over itself. Water has a viscosity of about 1 cP

Volumetric Flow Measurement

Volumetric flowmeters directly measure the volume of fluid passing through the flowmeter. The only

flowmeter technology that measures volume directly is the positive displacement flowmeter.

Vortex Precession

Vortex precession flowmeters use inlet vanes to rotate the fluid to form a vortex center (similar to a cyclone)

that rotates around the inside of the pipe. The rotation of the vortex can be related to the flow rate.

Vortex Shedding

Vortex shedding flowmeters alternately generate vortices on both sides of a bluff body located in the flow

stream. The number of vortices formed can be related to the flow rate.

Water

Water can exhibit different properties depending upon its impurities. Whereas water with many impurities

can be very conductive, de-ionized water is a form of pure water that is not very conductive. Boiler feed

water often softened or de-mineralized before it is fed into boilers.

http://www.flowmeters.com/ufm/index.cfm?task=magnetic

http://www.flowmeters.com/ufm/index.cfm?task=turbine

http://www.flowmeters.com/ufm/index.cfm?task=ultrasonic

http://www.flowmeters.com/ufm/index.cfm?task=vortex_fluidic

http://www.flowmeters.com/ufm/index.cfm?task=positive_displacement

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