Welch Allyn 35900-NP-TE, Инструкция по применению

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Appendix C: Test sequence
A complete test sequence consists of the following phases:
• AutoStart
• Calibration
• Test
AutoStart phase
The AutoStart phase determines when the calibration phase should proceed. Artifact
rejection is employed during the test phase to reduce the effect of transient noise
bursts.
Immediately after you press the test button, the AutoStart phase begins. AutoStart
checks both the quality and stability of the seal by measuring the response obtained
from a sequence of test tones. The stability of the seal is determined by comparing the
responses obtained over time. When the level of the response is within an acceptable
range and is stable over time, the unit proceeds to the calibration phase.
Calibration phase
DPOAE screener
The calibration phase calibrates the level of the tones that will be applied during the
actual test phase. The calibration phase automatically measures the response obtained
from a sequence of calibration tones and calculates the voltage needed to obtain the
desired intensity levels. If the desired peak pressure cannot be obtained, the unit will use
the maximum voltage. A successful calibration leads to the actual test phase.
TEOAE screener
The calibration phase automatically measures the peak pressure obtained from a
sequence of clicks and calculates the voltage required to obtain the target peak pressure.
If the desired peak pressure cannot be obtained, the unit will use the maximum voltage.
A successful calibration leads to the actual test phase.
Test phase
DPOAE screener
The test phase consists of measuring the response obtained from the pairs of test
frequencies (f1, f2) applied to the receivers. Two receivers are used, with each receiver
generating one frequency in order to reduce intermodulation distortion. Frequency
domain estimates of the actual L1, L2, distortion (DP) and noise floor (NF) are obtained
via the discrete Fourier Transform, with a bin resolution of approximately 31 Hz. The NF
estimate is obtained by averaging the power in the 4 closest (+/-2) bins to the DP bin.
TEOAE screener
The test phase consists of measuring the response obtained from repeated sequences
of clicks applied to the receivers. The click sequence is 3-1-1-1 repeated twice. Signal
and noise floor estimates are obtained by adding/subtracting the two response
sequences, respectively. The energy of the signal and noise floor estimates in various
Directions for use Appendices 59