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Recent Calibration Work at Los Alamos

Recent Calibration Work at Los Alamos. R.W. Whitaker, T.D. Sandoval, and D.O. Revelle Earth and Environmental Sciences Division Los Alamos National Laboratory Infrasound Workshop University of Hawaii Kona, Hawaii 11/12-15/01. Objective.

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Recent Calibration Work at Los Alamos

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  1. Recent Calibration Work at Los Alamos R.W. Whitaker, T.D. Sandoval, and D.O. Revelle Earth and Environmental Sciences Division Los Alamos National Laboratory Infrasound Workshop University of Hawaii Kona, Hawaii 11/12-15/01

  2. Objective • Using a traceable secondary sensor, achieve an independent calibration of the LANL piston-phone chamber • Select sensor • Check sensor at Sandia calibration lab • Work with LANL standards and calibration lab to make measurements

  3. Sensor • MKS Baratron 698A differential sensor • 0.1 Torr full scale (133.322 microbars) • Measurement side and Reference side • M side to chamber port • R side to large volume dewar • Data taken at 0.04 Hz • Analog signal to Geotech Instruments DL 24

  4. Data • Twenty minutes of signal, about 50 cycles at 0.04 Hz • 20 sps • CSS 3.0 flat files and wfdisc file • Analysis with Matlab and Matseis

  5. Analysis • Average all + peaks and - peak amplitudes, after filtering • Use NLINFIT (Matlab) over whole data record, single A0 • MKS Baratron 0 to 10 V for 0 to 0.1 Torr • Recal of digitizer V/count with a calibrated voltmeter • Peak to peak counts to volts, to Torr, to microbar (Pa)

  6. Calibration Chamber Sample output

  7. Day 200 of 2001 Baratron Data Raw data, bandpassed data, and segmented, bandpassed data Chamber with MKS Sensor (right)

  8. Measured and Fit of Baratron Data Fit Data

  9. Detail of Measured and Fit Data Fit Data

  10. MKS Baratron Data For the MKS sensor: 0 to 10 volts for 0 to 0.1Torr Torr = mmHg 133.3224 Pa/Torr Ncounts X (V/cnts) X (Torr/V) X (Pa/Torr) Ncounts * 3.78e-06 * 0.01 * 133.3224 and *2 if peak to peak

  11. Calibration Results Ambient P, D200/2001, 791.4 mbar Chamber constant from 4.223E-05 to 4.1429e-05 times P0 for microbars Doing 10 sequential Nlinfits over data, gives uncertainty of 0.1% for A0

  12. Summary • Achieved independent calibration of LANL calibration chamber • Earlier work was within 1.9% of current value • Establishes basis for use of chamber in sensor cals • Isolation from longer period ambient effects

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