Guralp Systems CMG-DM24S12AMS User Manual
Page 69
CMG-DM24S12AMS Operator's guide
Input calibration signal
strength (MB)
9856 counts
Returning signal
strength (Z3)
704512 counts
The calibration sheets provide us with the remaining values
needed to calibrate the sensor:
Sensor acceleration response
0.254 V/m/s
2
Equivalent accel. from 1V calibration
1.968 m/s
2
Digitiser input port sensitivity
3.507212 µV/Bit
Mux channel sensitivity
255.9253 µV/Bit
From these we know that the calibration signal is producing 9856
× 247 = 2434432 µV (2.434 V). This corresponds to an equivalent
input acceleration of 2.434 × 1.968 = 4.791 m/s
2
.
The sensor's acceleration response is given as 0.254 V/m/s
2
, so
that an acceleration of 4.791 m/s
2
will produce an output of 0.254
× 4.791 = 1.217 V (1216904 µV), which corresponds to a count
number at the digitiser's input port of 1216904 / 3.5 = 347687
counts.
Because the signal is transmitted differentially, the count number
observed at the digitiser should be double this: 695373 counts.
The actual signal at the digitiser of 704512 counts is within 1.5% of
this value, indicating that the sensor is adequately calibrated.
10.If you know the local value of g, you can also perform absolute
calibration by tilting the sensor by 90 ° and varying the
calibration signal until it precisely compensates for the signal
generated due to gravity.
March 2004
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