Guralp Systems CMG-3ESPCD - Manual (Page 37)

CMG-3ESPCD Digital Broadband Seismometer Calibrating the 3ESPCD
The bbnoisecal script automatically performs appropriate averaging
to reduce the effects of aliasing and cultural noise.
4.3.1 Sensor response codes
Sensor Sensor type code Units
(V/A)
CMG-3T or 3ESP, 30 s – 50 Hz response CMG­3_30S_50HZ V
CMG-3T or 3ESP, 60 s – 50 Hz response CMG­3_60S_50HZ V
CMG-3T or 3ESP, 100 s – 50 Hz response CMG­3_100S_50HZ V
CMG-3T or 3ESP, 120 s – 50 Hz response CMG­3_120S_50HZ V
CMG-3T or 3ESP, 360 s – 50 Hz response CMG­3_360S_50HZ V
CMG-3TB/3V/3ESP borehole, 30 s – 50 Hz CMG­3B_30S_50HZ V
CMG-3TB/3V/3ESP borehole, 100 s – 50 Hz CMG3B_100S_50HZ V
CMG-3TB/3V/3ESP borehole, 120 s – 50 Hz CMG3B_120S_50HZ V
4.4 The coil constant
The feedback coil constant K is measured at the time of manufacture, and
printed on the calibration sheet. Using this value will give good results at the
time of installation. However, it may change over time. The coil constant can
be determined by tilting the instrument and measuring its response to gravity.
To do this, you will need apparatus for measuring tilt angles accurately.
1. Measure the acceleration due to gravity, g, at your location.
2. Tilt the instrument slightly, and measure its attitude and the gain of the
mass position output for the component you wish to calibrate.
MAN-C3E-0002 37 Issue B - November 2013