GSB User Manual
GSB User Manual (593-01940-01 Rev C)
release date: TBD
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Tilt (for deployment)
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GPS status
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Field test results
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Battery state
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Memory usage
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Geographic coordinates
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Input noise (RMS)
5.1 – Instrument test
The instrument tests available for GSBs to be performed when they are connected
to GeoReaper are
Total Harmonic Distortion (THD)
: This test computes the total
harmonic distortion (THD) by the percentage of 8 harmonics over the
input sinusoidal signal at 31.25 Hz. The input switches are set to connect
to the test oscillator position, and a record is acquired to compute the
distortion. Test specifications are in Table 1.
Table 1: GSB THD Instrument Test
Gain Accuracy
: The gain accuracy test confirms that the gain
calibration applied by the channel yields the proper DC value. The test
uses the internal test oscillator to measure the various gain steps in a
series of 21 measurements. The first record measures a full scale test
oscillator reference DC signal through the output circuitry and is
compared with the value measured during the original gain calibration.
The next 7 measurements establish the DC offset at each gain by
measuring the signal across the internal resistors. The remaining
measurements stair-step the DC output signal of the test oscillator and the
ADC gain, first stepping down the test oscillator signal by 2:1, making a
measurement, increasing the gain by 2:1 and confirming that the
