Q-Sonic Plus Technology Advances

Prepared by: Charles Derr, Elster/Instromet

The Q-Sonic Plus is a technology improvement over previous

Instromet meters and a significant improvement over the world fleet of

multi-path Ultrasonic Meters (Usms). We will, herein, explain the

background hardware, measurement improvements, software and

firmware superior points in order to verify the background for this bold

statement. The Six Path Q-sonic Plus is comprised of 4 double-reflective

paths and 2 single reflective paths. This yields 16 different

mathematical “chord” slices of velocity information. (6 more than Krohne, 10

more than Honeywell, 12 more than Daniel, 12 more than FloSick600, 12 more than Cameron).

Some Usm vendors call each Chord, a Path. That is incorrect

terminology but sounds like they have more paths than they do. A

Chord is worth explaining in order to have the best grasp of what a

This Public Web Site picture below shows a four path, 4 Chord Meter sectioned view

graphical representation. This yields four velocity zone Chordal “slices” of the total

velocity profile. Example only: If this meter did 20 “shoot-arounds”/sec then you

would have 80 velocity-Chords/sec integrated into the average velocity integration.

Some Usm vendors routinely call each Chord, a Path. That is incorrect

terminology but sounds like they have more paths than they do. A

Chord is worth explaining in order to have the best grasp of what a

meter with only a few chords vs a meter with many more chords has

as inputs for its ability to integrate virtually all of the flow velocity

gradient zones inside the measurement section of the meter body.

Four “Paths”

Four “Zones”

Four “Beams”

Four “Chords”

Four “Velocity Slices”

Chords were used extensively in the early development of trigonometry.

The first known trigonometric table, compiled by Hipparchus, tabulated

the value of the chord function for every 7.5 degrees. In the second

century AD, Ptolemy of Alexandria compiled a more extensive table of

chords in his book on astronomy, giving the value of the chord for

angles ranging from 1/2 degree to 180 degrees by increments of half a

degree. The circle was of diameter 120, and the chord lengths are

accurate to two base-60 digits after the integer part.

The chord function is defined geometrically as in the picture to the left.

The chord of an angle is the length of the chord between two points on a

unit circle separated by that angle. The chord function can be related to

the modern sine function, by taking one of the points to be (1,0), and the

other point to be (cos , sin ), and then using the Pythagorean theorem

to calculate the chord length:

Chord History/Example/Definition:

A Usm “Path” is the geometric route and distance (whether it changes

directions enroute or not) between two transducers that are a

communication (transmit and receive) “Pair”. An ultrasonic frequency

transfers from the Piezo crystal to the titanium face of the transducer to

the gas and emits an ultrasonic sound pressure wave (measured in

Micro-pPascals of sound pressure; which travels through the gas and

arrives at the companion transducer face that it is acoustically “aimed”

at by direct aim or by reflective aim.

Any two points of tangency within the elongated circle of the cylinder

comprising the measurement-section “barrel” of the meter body, when

connected by a straight line, is one Chord or mathematical “slice” of

that cylinder and in Usm measurement terms; one “velocity-chord”.

The Q-sonic Plus has 4 double-reflective paths of 3 chords each giving

12 “slices” of the flow within the measurement section. The 2 single-

reflective transducer pairs each have one path and 2 chords, (another 4

chords). This yields 16 total chords on each meter during its sequential

activation of all 6 paths employing 6 pairs of transducers. Thus, one

“shoot-around” sees 16 pieces of the flow profile distribution within the

meter measurement section. Whether a multipath Usm is a take-off of

the original expired British Gas or Westinghouse-2 patents, or others,

the 4 path point-to-point meters see 4 total slices of the profile velocity

distribution. At 30 complete shoot arounds per second (and16 chords),

each second the Q-sonic Plus totalizes a velocity distribution

integration of 480 Chord velocity-sectors! The three-dimensional flow

velocity dynamics of pipeline Turbulent flow is better

dimensionalized by the most angles viewed the fastest. This is three,

(chord count/zones, chord lengths and timing resolution), of several

very fundamental reasons for the inherent accuracy of the Q-sonic Plus,

however, there are several others.

Four path and dual 4 path meters on the market range from 10 to

60+ shoot-arounds per second. 4 chords * 10 is 40 Chord

velocity-sectors/sec. 4 Chords * 60 shoot-arounds per second is

a total of 240 Chord velocity-sectors/sec., (however, they are

still constrained by 4 chords as opposed to 16 chord sectors). 16

“velocity-zones” of the flow distribution profile yields more

information than 4 “velocity-zones”.

Another consideration of final accuracy in a Usm is its ability to

accurately measure speed of sound. The speed of sound has a

two to one error factor vs velocity. A one percent error in the

measurement of speed of sound equals a two percent error in

velocity and resultantly the average velocity and when

multiplied by the meter area; Actual Volume Rate!

Below are two (very typical for the Q-Sonic Plus series) recent

certified calibration report/graphs of speed of sound as found on

these meters:

Usms have a finite time base “resolution”, (the smallest increment of

time that they are capable of measuring). The +/- time resolution

capability is a constant increment for a given meter’s applied

technology and crystal time base design. The Path transit time, +/- the

time base resolution gives the accuracy of the real transit time

measurement.

The Q-sonic Plus has four double reflection paths giving four LONG path

lengths. Each double reflective path length is approximately 3X the

length of a point-to-point direct path, for the same given diameter

meter. This means that the time base accuracy +/- applied to each

transit time measurement is only appr. 1/3rd of the error in transit time;

resulting in VERY accurate Speed of Sound measurements and

incrementally; transit time measurement.

Examine the data sheet below for one 12” Qsonic Plus meter. Observe

that the double-reflective paths are appr. 2.84 feet; or, 34 inches. Most

12” point-to-point meters would have a longest path of 11 to 12 inches.

Having 3X the path length gives much better transit time resolution,

therefore speed of sound accuracy, therefore final average velocity

accuracy and finally; better volume accuracy.

12” Qsonic Plus Spool data below:

The following is a recent calibration of a Q-sonic Plus:

Note: LONG

path lengths

for a 12”

meter giving

HIGH

resolution of

SOS/transit

time

Meter Details: Certificate Number: 6275 Meter Serial Number

7407

Manufacturer

Elster-Instromet

Model

Qsonic-Plus

Meter I.D.

22.0629 in

0.5604 meters Meter Capacity

942902 acf/h

26700 acm/h

Flow Conditioner CPA 50E Type A

Test Conditions(Avg)

Medium

Natural Gas

Pressure

838.88 psia

5783.90 kPa Temperature

69.68 °F

20.93 °C

Density

2.76 lbs/ft3

44.28 kg/m3 Compressibility 0.8936869

SOS Comparison [Meter vs AGA-10]

FlowRate Gas Velocity

Meter SOS Calc. SOS

SOS Deviation

SOS Deviation

(m3/hr) (m/s) (m/s) (m/s) (m/s) (%)

24298 27.36 421.45 421.42 0.03 0.01

20094 22.63 420.80 420.75 0.05 0.01

13418 15.11 420.71 420.68 0.03 0.01

9269 10.44 422.41 422.36 0.05 0.01

5371 6.05 422.56 422.51 0.05 0.01

2692 3.03 422.11 422.05 0.06 0.01

542 0.61 421.63 421.58 0.05 0.01

The table below is the actual “As Found”

Measured –vs- AGA 10 Calculated Speed of Sound

The data above is the result of 6 paths, 16 chords, 2 long and 4

very long paths; running 16 chords at 30 hz and yielding 480

velocity-chords/sec, measured. This is where a large portion of

the “Inherent Accuracy” is originated. This is an amazing

“Natural Linearity” or “out-of-the-box” Linearity and is a

common calibration test result, for the Q-Sonic Plus series.

-1.00-0.80-0.60-0.40-0.200.000.200.400.600.801.00

0 5 10 15 20 25 30

SO

S D

evia

tio

n [

Un

its i

n

tab

le]

Gas Velocity [Units in table]

SOS Comparison [Meter vs AGA-10]

Precise timing gives a Usm…only Precision...then: Repeatable

timing gives a Usm….Precise repeatable timing….then:

Linearity gives near-same small error across the range..then :

Calibration factors bring each calibrated velocity to the accuracy

point of the calibration reference system…adding up to:

A Precise, Repeatable , Linear, Accurate Meter

Meter output

tested: Frequency

None

FE/FIT-03161

14-0143-PS2406X, 14-0144-PS2406X, 14-0145-

PS2406X

UST 3048mm, CPA 50E, UST 6096mm, METER, DST

3048mm

CPA 50E Type A

Shown below is a Q-Sonic Plus with the protective

stainless wire covers removed, the transducer and block

and cable installed, the onboard pressure transducer

installed, the explosion-proof 7-data group color touch-

screen local display and a Transmitter with the CPU, et.

Shown inside a plexi-glass depiction of the standard

aluminum or stainless canister.

The Q-Sonic Plus employs Very Highly Advanced Signal

Processing:

The “Coded Multi Burst” is a Signal Processing Advantage in High

Ultrasonic Noise Backgrounds (Caused by Valves, Regulators, Etc.):

Traditional Methods of Noise reduction

• Averaging / Stacking • Improvement of SNR when the noise is

asynchronous • No improvement of SNR when noise is synchronous • Transit times variation (jitter) causes signal blurring

• Filtering • Improves SNR for out of frequency band noise • Does not help when noise is in frequency band

The Titanium Encapsulated, Low power, Intrinsically Safe

Transducers as shown installed (above) are a great part of

the Q-Sonic Plus Success Story as are the 90 degree ports

having no pocket turbulence “scooping” effect. These

Hardware Differentiators are vitally important: especially so

when combined with Advanced Signal Processing!

•

Coded Multi Burst with and without noise

present

Coded Multiple Burst

• Improvement of signal to noise

(High speed averaging in combination with a unique code)

• Without any delay

(Efficiently usage of UFM operating time) • Requires transducer with broad band

characteristics

(Coded signal cannot pass through narrow band transducer)

Very special transducers are needed to do high speed Coded Multi Burst……they must be broad band, fast and have a fast (low) delay time.

The transducer design accomplished for the Q-Sonic Plus is the new “Raised-Bar” for others to reach for in the future; but are the standard for all current production Elster/Instromet Usms. They are a true advanced technology.

-2.00

-1.60

-1.20

-0.80

-0.40

0.00

0.40

0.80

1.20

1.60

2.00

0 5000 10000 15000 20000 25000

Dev

iati

on

[%

]

Flow

As found As left Ver Pt1 Ver Pt2

I.E: 60 Deg

Sharp-edged “oval-entry” port causes pocket-turbulence

Small, low volume, 90 Deg port gives exceedingly small pocket-turbulence

Q-Sonic Plus Technique

The Majority of the Usm Fleet Technique

Transducer Port bore-

entry Cross-sectional

view