Dynamic Calibration of Pressure Transducers

Transcription

1 Dynamic Calibration of Pressure Transducers 7 th Workshop on Analysis of Dynamic Measurements Paris, October 15-16, 2012 Edwin van de Bunt, Arthur Bouvy, MARIN

2 Outline of the presentation Introduction to the project Why do we need a dynamic calibration? The dynamic calibration: cone drop tests The calibration filter Conclusions 2

3 An example of a wave impact 3

4 High speed video of a wave impact 4

5 Static versus Dynamic calibration Keller piezo resistive miniature transducer Pressure range: 0 to 100 bar; Natural frequency > 1 MHz Silicone elastomer to reduce temperature shock No information from manufacturer except a static calibration certificate Different suppliers of the die : the transducers come in batches 5

6 Dynamic Pressure Calibration Since the late 1950 s Periodic, Aperiodic Impulse calibrator, Shock tubes, Spark plugs In general: the dynamic calibration setup should fairly accurate mimic the measurement application Our method: Water impact High pressures 6

7 Free drop test of a cone: the Truth Wagner theory (1932): analytical solution for idealized situation Modern analytical and numerical solutions for non-idealized situations Cone before impact Height Dead rise angle Cone on impact Free surface at rest 7

8 The cone P4 Data acquisition system Connector to spiral cable P6 Y-Axis P1 P8 X-Axis P2 Z-Axis P7 P3 P5 Pressure transducer Accelerometers Water contact sensor Pressure transducer Extra weights 8

9 Data Acquisition and measurement channels Single shot system with ring buffer (4 seconds) 16 channels Sample rate 50 khz Water contact sensor Eight pressure transducer channels Three accelerometers: X,Y,Z 9

10 Tension spindles (3x) Tension motor The shooting device Junction box Spiral cable Tension plate Tension springs (15x) Tension magnets (6x) Tension chucks Launcher Retractor spindles Launcher damper (3x) Retractor motor Retractor magnets (6x) Projectile chucks (3x) Projectile damper (3x) Projectile bucket Projectile Gates 10

11 An example of a measurement 11

12 The measurements On the cone are eight transducers For every batch 10 measurements are taken The measurements for every transducer are aligned in time 12

13 Directional corrections of the cone impact 13

14 Time averaging pulse pressure over membrane surface 2 mm 14

15 Numerical and measured pressure pulses 15

16 Effect of transducer and conditioner channel The dynamic response of the transducer The surface size of the transducer The dynamic response of the analogue conditioner channel: specifically the anti aliasing filter The limited sampling frequency 16

17 Effect of sampling on the pressure pulse 17

18 The calibration scheme Measurements Physical pulse Pressure transducer Analoge low pass filtering 50 khz Interpolation to 1 MHz Numerical pulse Numerical simulations Integration for surface Compare! 18

19 The estimation Black box method: input = numerical pulse; output = measured pulse Estimate the transfer function from input to output Use the inverse transfer function as calibration filter Example: n b0 bz 1 b2z b3z... bn z H( z) n az az az az b0 b1 b2 b a0 a1 a2 a n 19

20 The Calibration Filter 20

21 Intended effects of the calibration filter Assuring the traceability (..?) Correct for the effects of the anti-aliasing filter Correct for the limited bandwidth of the measurement channel 21

22 Numerical, Measured and Calibrated pulses 22

23 The reproducibility 23

24 Conclusions Dynamic calibration is feasible but cumbersome Drop tests are good for transducer testing Temperature shock Only at 1 MHz the high frequency content is available: do not downsample! Add information that is not there through the calibration Better balance between the truth and the measurand 24

25 Literature Gazzola, T., Korobkin, A., Malenica, S., Scolan, Y-M. Three-dimensional Wagner problem using variational inequalities In proceedings of the International Workshop on Water Waves and Floating Bodies (2005), vol. 20. Gazzola, T., Korobkin, A., Malenica, S. Hydro-elastic Wagner impact using variational inequalities Tveitnes, T. fairlie-clarke, A.C., Varyani, K., An experimental investigation into the constant velocity water entry of wedgeshaped sections Ocean engineering 35 (2008), Wagner, H., Über Stoβ und Gleitvorgänge an der Oberfläche von Flüssigkeiten Zeitschrift für angewandte Mathemathik und Mechanik 12 (1932),

26 Thank you for your attention! It is now time for questions! 26