Assignment#01: Literature Survey on Sensors ECE 5320 Mechatronics Assignment#01: Literature Survey on Sensors Topic: Piezoelectric Quartz Accelerometers Prepared by: Jared B. Bowler Dept. of Electrical and Computer Engineering Utah State University Phone: (435) ; 3/11/2005

03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors Outline –Reference list –Links to explore this topic further –Basic working principles illustrated –Major applications –A typical configuration in application –Major specifications –Relevant issues in applications: advantages, disadvantages, how to select, cost information, and places to purchase. –Conclusion

03/10/05 Reference list Mechatronics Handbook to ECE5320 Mechatronics. Assignment#1 Survey on sensors

03/10/05 For further exploration….. (Survival pointers of web references) ECE5320 Mechatronics. Assignment#1 Survey on sensors

Basic Working Theory: Piezoelectric Principles Piezoelectric effect discovered by Pierre and Jacques Curie in 1880 They discovered that under certain conditions such as when quartz is stressed along its main axis, the quartz will generate an electrical field Now this effect is primarily used in sensing and actuating engineering applications 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Classes of Piezoelectric Materials Natural, such as quartz Synthetic crystals Polarized ferroelectric ceramics Some Polymer films 03/10/05 Piezoelectric Materials fall into 4 main categories ECE5320 Mechatronics. Assignment#1 Survey on sensors

Classes of Piezoelectric Materials Most piezoelectric accelerometers use polarized ferroelectric ceramics or quartz crystal In accelerometers, lead zirconate titanate (PZT) and quartz crystals are most common High performance and physical robustness are two main reasons for using the above materials in engineering applications 03/10/05 Piezoelectric Materials—Engineering ECE5320 Mechatronics. Assignment#1 Survey on sensors

Overview: What it is “Most piezoelectric accelerometers are made of quartz crystal, piezoelectric ceramics, or, for high-temperature operation, tourmaline or lithium niobate. They obey Newton’s second law, F = ma, in that the force acting on the measuring element is directly proportional to the acceleration produced. Available in a wide range of configurations and operating specifications, these devices are used wherever shock or vibration is of interest.” 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Two types of quartz accelerometers High impedance: More versatile, most parameters can be controlled by an external charge amplifier, more robust. Low impedance: More customized application, can be cheaper, but not for broad applications 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Why Choose Quartz instead of PZT? “Material stress limit of ~20,000 psi Temperature resistance up to 930°F Very high rigidity, high linearity, and negligible hysteresis Almost constant sensitivity over a wide temperature range Ultra-high insulation resistance (1014 ), allowing low- frequency measurements (<1 Hz)” 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Basic Working Theory: Piezoelectric Effect in Crystals 03/10/05 “A) Longitudinal Effect. The size of the charge depends only on the force applied. The only way to increase this charge is to connect several plates mechanically in series and electrically in parallel. B) Shear Effect. This effect, too, is independent of the size and shape of the piezoelectric element as well as of the charge distribution. The charge occurs at the surfaces under load; at n elements connected mechanically in series C)Transverse Effect. In this case, a force in the direction of one of the neutral axes produces a charge on the surfaces of the corresponding polar axis.” ECE5320 Mechatronics. Assignment#1 Survey on sensors

Basic Working Theory: Manufacture of Piezoelectric Quartz 03/10/05 “Figure 1. Piezoelectric crystals that are cut so that they exhibit the longitudinal effect (A) are sensitive to compression forces. They are used primarily to measure force, pressure, strain, and acceleration. The transverse effect (B) makes it possible to obtain a greater charge by suitable shaping and arrangement of the piezoelectric elements, and is used primarily in pressure sensors. Shear effect elements (C) are chiefly used in accelerometers and 3-component force sensors. They have low base-strain sensitivity (the amount of strains in an object under test that are transmitted via the base plate to the sensor element) and a well- behaved response to rapid temperature changes because these influences act in a direction perpendicular to the sensitive shear axis.” ECE5320 Mechatronics. Assignment#1 Survey on sensors

03/10/05 Major applications of Piezoelectric Quartz Accelerometers I “Aerospace. Modal testing, wind tunnel, and shock tube instrumentation; landing gear hydraulics; rocketry; structures; ejection systems Ballistics. Combustion, explosion, and detonation Engine Testing. Combustion and dynamic stressing” ECE5320 Mechatronics. Assignment#1 Survey on sensors

03/10/05 Major applications of Piezoelectric Quartz Accelerometers II “Engineering. Materials evaluation, control systems, reactors, structural analysis, auto chassis structural testing, shock and vibration isolation, and dynamic response testing Industrial/Factory. Machining systems, metal cutting, and machine health monitoring OEMs. Transportation systems, rockets, machine tools, engines, flexible structures, and shock/vibration testers” ECE5320 Mechatronics. Assignment#1 Survey on sensors

Quartz Accelerometers: Specifics 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors Active electrical systems Produce an output only when there is a change in the load Best suited for dynamic measurements However, with the proper hardware, they can also accurately measure relatively static systems

Typical Configuration: Wilcoxon Accelerometers These sensors are hermetically sealed. Outer housing is 316L stainless steel, which is corrosion resistant. These sensors are particularly appropriate for industrial environments, due to their ability to work even in harsh operating conditions. 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Example: Wilcoxon Model 785A Low Profile Industrial Accelerometer Sensitivity mV/g Acceleration Range g peak Amplitude non-linearity % Frequency Response (3dB) ,000 Hz Resonant Frequency KHz Transverse Sensitivity % of axial 03/10/05 Major Specifications : Dynamic ECE5320 Mechatronics. Assignment#1 Survey on sensors

Model PDA130 High Speed Piezoelectric Micro-positioning Motor. Power Requirement: voltage source VDC current regulating diode mA Electrical Noise, equiv. g, nominal: Broadband 2.5 Hz to 25 kHz ,260 μg Spectral 10 Hz μg/√Hz 100 Hz μg/√Hz 1000 Hz μg/√Hz Output Impedance Ω Bias Output Voltage, nominal VDC 03/10/05 Major Specifications: Electrical ECE5320 Mechatronics. Assignment#1 Survey on sensors

Advantages “Extremely wide dynamic range, almost free of noise - suitable for shock measurement as well as for almost imperceptible vibration Excellent linearity over their dynamic range Wide frequency range, high frequencies can be measured Compact yet highly sensitive No moving parts - long service life Self-generating - no external power required Great variety of models available for nearly any purpose Integration of the output signal provides velocity and displacement” 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Disadvantages Relative high price Need higher power System must be changing somewhat, purely static measurements are impossible to make 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Criteria for Selection Type of sensing needed (force, shocks, etc) Temperature Range Nature of the environment (temperature) Nature of the system measured (static, dynamic) Resolution Cost 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Cost information Can range widely from a few dollars to hundreds of dollars Wide variety of configurations available The example looked at was priced at $150 USD 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Places to purchase Do a Google or Froogle search for “piezoelectric accelerometers,” there are many results One distributor found Reliability Direct, which distributes Wilcoxon Accelerometers 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors

Conclusion Piezoelectric Accelerometers offer unique characteristics due to their design that are not often found in other types of sensors. However, they are not necessarily for every application. Be sure to weigh the pros and cons and take a close look at the sensor specs 03/10/05 ECE5320 Mechatronics. Assignment#1 Survey on sensors