Transducer calibration

Figure I Simulation of a transducer calibration test, a) Calibration configuration T45° transducer and 6 flat bottom holes at various depths b) Predicted field by Champ-Sons c) Simulated Bscan d) Echodynamic curve.

A calibration check of controllers should be made on a regular basis. The ISO 9000 standard reviews developing the frequency calibration checks. A visual examination should be made before proceeding with the check to determine that no damage exists. Some of the more common problems caused by a plant s hostile environment that can effect equipment such as sensors/transducers are noise interference, mounting holes (must be concentric and clean), installation, diaphragm considerations, and transducer calibration. Zero balance, full-scale sensitivity, and R-cal at 80% parameter reference points for calibration can be used. The sensor/transducer manufacturer provides these parameters.154... 

Underwater acoustics is routinely used in laboratory-scale test facilities for flaw detection, transducer calibration, material property evaluations, and acoustic visualization. In a typical underwater acoustic study, an object of interest is submerged in a water filled tank and acoustically illuminated (insonified). The acoustic signals scattered by the object are then measured and analyzed. If the tank used is not sufficiently large, these measured acoustic signals will include spurious echo components due to extraneous wall reflections. Since the effect of these contaminating echoes usually cannot be removed from the resulting data set by post analysis, they must be prevented from occurring at their source. One cost... 

Traceability The step-by-step transfer process by which the transducer calibration can be related to primary standards. During any calibration process, transducer is compared to a known standard. National or international institutions usually prescribe the standards. In the United States, such governing body is the NIST. 

Temperature control and measurement and pressure transducer calibration is also covered, and lest procedures with typical temperatures for specific polymers are given. 

ISO-9000 certification ISO-9000 and lSO-9004 are guidelines that interpret the requirements of the three main standards—ISO-9001 (the quality system in design and development), ISO-9002 (the quality system for quality assurance in production and installation), and ISO-9003 (the quality system for quality assurance in final inspection and testing). These three standards define the quality-system requirements for firms with a varying scope of business requirements. See design verification fabricating, world-class processor certification productivity quality system test certification testing and quality control transducer calibration. 

Breckenridge FR (1982) Acoustic emission transducer calibration by means of the seismic surface pulse. J. Acoustic Emission 1(2) 87-94... 

Pressure transducer Calibration only 1400 MPa 120 °C higher possible Process pressure controlling... 

Currently, most manufacturers use automatic data gathering. Hcrf, pressure signals will be obtained by the use of transducers. Under lliesc circumstances, the transducers should be calibrated per code and certiHed... 

The second, mechanical and electrical manometers, require more frequent calibration. Changes in the elastic properties of the pressure transducer, wearing in mechanical parts, and electronic circuitry drift influence the properties of the instruments, giving rise to repeated calibration. 

This aspect is not included here, but is related to optical flow diagnostics. It is based again on the principle of the optical Doppler effect. Multifunctional equipment is available for noncontact measurements of flow-induced vibration on surfaces of structural elements, for acoustic measurements, and for calibration of accelerometers and vibration transducers. 

The important characteristics of a transducer used in conjunction with an electronic measurement system are accuracy, susceptibility, frequency, impedance and, if appropriate, the method of excitation. The transducer is likely to be the least accurate component in the system, and it should be calibrated (and recalibrated) at frequent intervals. It is likely to be subject to a range of different physical conditions, some of which it is there to detect and others by which it should remain unaffected (for example, a pressure transducer should be unaffected by any changes in temperature which it might be called upon to experience). Some types of transducer are not suitable for use under D.C. conditions and all will have an upper limit of frequency at which accuracy is acceptable. Many types of transducer are also affected by stray electromagnetic fields. 

The major limitation of velocity transducers is their sensitivity to mechanical and thermal damage. Normal use can cause a loss of calibration and, therefore, a strict recalibration program is required to prevent data errors. At a minimum, velocity transducers should be re-calibrated every six months. Even with periodic re-calibration, however, velocity transducers are prone to provide distorted data due to loss of calibration. 

Calibration of the quartz oscillators was performed by consequent deposition of the cadmium arachidate layers (Facci et al. 1993). The dependence of the frequency shift on the number of deposited bilayers is shown in Figure 46. The analysis of the curve reveals a sensitivity of 1.482 pg/mm Hz for our transducer. 

With the multitude of transducer possibilities in terms of electrode material, electrode number, and cell design, it becomes important to be able to evaluate the performance of an LCEC system in some consistent and meaningful maimer. Two frequently confused and misused terms for evaluation of LCEC systems are sensitivity and detection limit . Sensitivity refers to the ratio of output signal to input analyte amount generally expressed for LCEC as peak current per injected equivalents (nA/neq or nA/nmol). It can also be useful to define the sensitivity in terms of peak area per injected equivalents (coulombs/neq) so that the detector conversion efficiency is obvious. Sensitivity thus refers to the slope of the calibration curve. 

What if instruments could be designed which were remoteiy self-calibrating with respect to calibration services of a National Metrology Institute (NMI) While this may sound very far-fetched , it is not difficult to speculate that future application of telemetry, transducers, intrinsic standards, detectors and computers will link some instruments directly to a NMI to obviate their need for RMs (Rasberry 1998). 

Fig. 3.5 Principle of a laser interferometer for absolute calibration of the transducer velocity. Li and L2 denote the lengths of the two light paths of the split laser beam, giving a path difference A5 = 2(Li - L2)...

Fig. 3.16 Schematic drawing of the MIMOS II Mossbauer spectrometer. The position of the loudspeaker type velocity transducer to which both the reference and main Co/Rh sources are attached is shown. The room temperature transmission spectrum for a prototype internal reference standard shows the peaks corresponding to hematite (a-Fe203), a-Fe, and magnetite (Fe304). The internal reference standards for MIMOS II flight units are hematite, magnetite, and metallic iron. The backscatter spectrum for magnetite (from the external CCT (Compositional Calibration Target) on the rover) is also shown...

To minimize experiment time a very strong Co/Rh source was used, with an initial source strength of about 350 mCi at launch. Instrument internal calibration is accomplished by a second, less intense radioactive source mounted on the end of the velocity transducer opposite to the main source and in transmission measurement geometry with a reference sample. For further details, see the technical description in Sect. 3.3. 

Fig. 3.7.4 (A) CRMI results of pressure versus volume on the Berea sandstone sample with a porosity of 20% and permeability 0.2 darcy. The two lines are raw CRMI data and the corrected data by a calibration run. Transducer noise was also filtered. The amount of the correction is fairly small and the two data sets overlap. (B) CRMI pore body volume distribution showing a predominant peak at around 20 nL. Figure from Ref. [57] with permis-...

Wayment DG, Casadonte DJ (2002) Design and calibration of a single-transducer variable-frequency sonication system. Ultrason Sonochem 9 189-195... 

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