Finally, we have found the correct calibration of Guralp and STS2 seismometers.

ADC: 2¹⁶counts = 20V Hence, calibration of ADC is 3.2768e+03 counts/V.

GURALP

Sensitivity of seismometer = 800 V/ms^-1

Gain of the guralp breakout box (reference elog entry) = 20

Calibration = 3.2768e+03 counts/V x 800  V/ms^-1 x 20 = 52428800 counts/ms^-1 -----> 1.9073e-08 ms^-1/count

STS

Sensitivity = 1500 V/ms^-1

Gain of the STS electronic breakout box = 10

Calibration = 3.2768e+03 counts/V x 1500  V/ms^-1 x 10 = 49152000 counts/ms^-1 -----> 2.0345e-08 ms^-1/count