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Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Quartz Crystal Technology Introduction Design of Quartz Resonant Sensors Design of Pressure.

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Presentation on theme: "Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Quartz Crystal Technology Introduction Design of Quartz Resonant Sensors Design of Pressure."— Presentation transcript:

1 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Quartz Crystal Technology Introduction Design of Quartz Resonant Sensors Design of Pressure Transducers Transducer Characteristics & Performance Applications Home Page

2 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Introduction The widespread use of digital computers and digital control systems have generated a need for high accuracy, inherently digital sensors. This presentation will discuss the design, construction, performance, and applications of resonant quartz crystal pressure transducers. Home Page

3 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Background Paroscientific is the leader in the field of precision pressure measurement. The company was founded in 1972 by Jerome M. Paros after a decade of research on digital force sensors. Application of this technology to the pressure instrumentation field resulted in transducers of the highest quality and superior performance. Precision comparable to the best primary standards is achieved through the use of a special quartz crystal resonator whose frequency of oscillation varies with pressure induced stress. A quartz crystal temperature signal is provided to thermally compensate the calculated pressure and achieve high accuracy over a wide range of temperatures. Home Page

4 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Material Properties and Characteristics of Quartz Sensors Piezoelectric [pressure-charge generation] Anisotropic [direction-dependent] –Elastic Modulus –Piezoelectric Constants –Coefficient of Thermal Expansion –Optical Index of Refraction –Velocity of Propagation –Hardness –Solubility [etch rate] –Thermal and Electrical conductivity Home Page

5 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation High Resolution : More precise measurements can be made in the time domain than the analog domain. Excellent Accuracy : The quartz crystal sensors have superior elastic properties resulting in excellent repeatability and low hysteresis. Long Term Stability : Quartz crystals are very stable and are commonly used as frequency standards in counter-timers, clocks, and communication systems. Low Power Consumption Low Temperature Sensitivity Low Susceptibility to Interference Easy to Transmit Over Long Distances Easy to Interface With Counter-Timers, Telemetry, and Digital Computer Systems Advantages of Quartz Resonant Sensors Home Page

6 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Design of Quartz Resonant Sensors Single Beam Force Sensors Double-Ended Tuning Fork Force Sensors Torsional Temperature Sensors Home Page

7 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Single Beam Force Sensor Drawing Flexure Relief Isolator Spring Input Force Vibrating Beam (Electrodes on Both Sides) Isolator Mass Mounting Surface The beam is driven piezoelectrically at its resonant frequency. Isolator masses and springs act as a low- pass mechanical filter to minimize energy losses to the mounting pads resulting in high Q oscillations. Single Beam Force Sensor Home Page

8 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Single Beam Force Sensor Photo Loads applied to the mounting pads change the resonant frequency of the beam. The change in frequency is a measure of the applied loads. Home Page

9 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Double-Ended Tuning Fork Force Sensors Drawing Electrical Exitation Pads Surface Electrodes Dual Tine Resonators Mounting Pad Applied Load Two tines vibrate in opposition to minimize energy losses Applied Load Double-Ended Tuning Fork Force Sensors Home Page

10 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Double-Ended Tuning Fork Force Sensors Photo Produced on quartz wafers by photolithographic and chemical milling techniques similar to fabrication of watch crystals Home Page

11 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation 0 Full Scale Compression Full Scale Tension 10% Change in Period with Full Scale Load Resonant Period (microseconds) Output Period vs. Force Home Page

12 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Nominal Period of Oscillation=5.8 microseconds Nominal Temperature Sensitivity=45 ppm/ 0 C Electrical Exitation Pads Dual Torsionally Oscilating Tines Mounting Pad Quartz resonator used for digital temperature compensation Torsional Resonator Temperature Sensor Home Page

13 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation The change in resonant period output is a measure of temperature used for thermal compensation of the pressure crystal output. Wafer of Temperature Sensors Home Page

14 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Internal Vacuum Balance Weight Bourdon Tube Quartz Crystal Resonator Force Sensor Case Quartz Resonator Temperature Sensor Bellows Pressure Input Balance Weight Quartz Crystal Resonator Force Sensor Quartz Resonator Temperature Sensor Input Pressure Pressures applied to the bellows or Bourdon tube load the Quartz Force Sensors to change the resonant frequencies. Quartz Temperature Sensors provide thermal compensation. Quartz Crystal Resonator Pressure Transducers Home Page

15 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Balance weights provide acceleration compensation. The mechanism is hermetically sealed and evacuated. The internal vacuum maximizes the crystal Q and serves as the reference in absolute pressure sensors. Digiquartz ® Barometer Home Page

16 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Pressure Signal Timebase Clock Time N Periods Time t=Sensor Output Period= 1/Resonant Frequency N=Number of Periods Transducer period output, t, gates a high frequency clock, f c, for N periods and the clock pulses are counted. (f c ) Period Measurement Resolution and Sampling Home Page

17 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Sampling Time = N Period Resolution =+/- 1 Count/(Total Counts)=+/- 1 / (N f c ) = +/- 1 / (Sampling Time) f c ) Force Resolution = +/- 10 / (N f c ) (Only 10% of the counts are related to Force) Example: If clock =20 MHz and sampling time=1 second then the Force Resolution=5x10 -7 Full Scale Continued Pressure Signal Timebase Clock Time N Periods Time Home Page

18 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Force = C[ / 2 ] [1-D( / 2 )] =Force Resonator Period Output C=Scale Factor in Desired Engineering Units D=Linearization Coefficient 0 =Period Output at No Load (Force=0) U=(Temperature Sensor Period)-(Temperature Period at zero 0 C) 0 = U+ 3 U U U 4 C=C 1 +C 2 U+C 3 U 2 D=D 1 +D 2 U Temperature =Y 1 U+Y 2 U 2 +Y 3 U 3 ( 0 C) Linearization and Temperature Compensation Home Page

19 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Multiplexer Counter Microprocessor Shift Store Pass On Serial Interface EEPROM EPROM 15 Mhz Clock Transducer Pressure SignalTemperature Signal RS-232 or RS-485 In RS-232 or RS-485 Out Intelligent Instrumentation Home Page

20 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Resolution Static Error Band – Non-repeatability – Hysteresis – Conformance Environmental Errors – Temperature – Acceleration Long Term Stability Transducer Characteristics and Performance Home Page

21 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Noise Versus Record Length Parts per billion in seconds Parts per million for years Home Page

22 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Paroscientific, Inc. Digiquartz ® ® Pressure Instrumentation Tsunami Detection (Earthquake Generated Tidal Waves) Sensitivity of 1 mm of Water at Depths of 6000 meters Home Page

23 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Measured at 10,000 PSI +5ppm Height (cm) S/N 1064 S Class 200 PSI/Kg Piston Measuring piston wear to less than a nanometer High Resolution Measurements of Dead Weight Tester Piston Taper Home Page

24 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Number of Units Pressure Hysteresis in Microbars Mean Hysteresis -1.3 Microbars Pressure Hysteresis Measurements on Twenty- Three Paroscientific Barometers Home Page

25 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Static Error Band (Non-Repeatability, Hysteresis, Non-Conformance) Home Page

26 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Total Error Band (Over Temperature at Various Pressures) Home Page

27 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Long Term Stability Median Drift Rate= hPa = ( inHg) per year Home Page

28 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Paroscientific manufactures and sells a complete line of high precision pressure instrumentation. Resolution of better than % and typical accuracy of 0.01% are achieved even under difficult environmental conditions. Other desirable characteristics include high reliability, low power consumption, and excellent long- term stability. Over 30 full scale pressure ranges are available - from a fraction of an atmosphere to thousands of atmospheres (3 psid to 40,000 psia). Absolute, gauge, and differential transducers have been packaged in a variety of configurations including intelligent transmitters, depth sensors, portable standards, water level systems and meteorological measurement systems. Intelligent electronics have two-way digital interfaces that allow the user to adjust sample rates, resolution, engineering units, and other operational parameters. Digiquartz ® products are successfully used in such diverse fields as hydrology, aerospace, meteorology, oceanography, process control, energy exploration, and laboratory instrumentation. Paroscientific, Inc. Overview Home Page

29 Paroscientific, Inc. Digiquartz ® Pressure Instrumentation Metrology Hydrology Meteorology Oceanography Aerospace Process Control Energy Exploration Digiquartz ® Application Areas Home Page


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