GSB User Manual
GSB User Manual (593-01940-01 Rev C)
release date: TBD
Page 25 of 27
calculates the impedance using the RMS voltage measured. A
comparison vs thresholds (lower and upper limits) set by the user
provides a pass/fail result.
•
Total Harmonic Distortion (THD)
: This is used to analyze the amount
of harmonics of the internal sensor(s). To perform the THD test, the
device’s test signal generator provides a known amplitude and frequency
signal to the analog input and compares the amplitude of the measured
fundamental frequency with the amplitude of its harmonics. No
parameters settings are requested for this test.
•
Geophone CMRR
: This allows evaluating the balance of the internal
sensor(s) analog input by testing the device’s rejection of unwanted
signals common to both input pins. Results may be affected by leakage,
bad sensors, and high ambient noise.
To perform CMRR test, the GSB test signal generator provides a sine
wave of known amplitude (90% of full scale) and frequency selected by
user to both analog pins and evaluates the ratio of the RMS value of the
output voltage vs the ADC input. A comparison vs maximum ratio
selected by user provides a pass/fail result.
•
Geophone Crossfeed
: This is a test valid only for GSB-3s. It evaluates
the amount of energy that can be transferred to a different channel.
The test requires a record for each channel. For each record, one
channel’s input switch is set to the sensor oscillator/sensor position while
the other channels are connected to the sensor. The active channel is
driven with a 31.25Hz sinusoidal signal at full scale and the induced
Crossfeed voltage on the other channels is measured. A comparison vs
maximum ratio selected by user provides a pass/fail result.