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