[Aritomi, Kita, K. Tanaka, K. Nagano, Akutsu]

 

To check the polarity of geophones, we excited LVDT coils (VIS-TMSX_COILOUTF_**_EXC) and measured relative phase of LVDT signals (VIS-TMSX_LVDTINF_**_OUT) and geophone signals (VIS-TMSX_ACCINF_**_OUT).

Attached figure is the transfer fucntion from LVDT V1 signal to geophone V1 signal. Between 3-7 Hz, relative phase is around -90 deg . (after 8 Hz there is sneak current of LVDTs)

The results are as follows.

 

Geophone V1: neg

Geophone V2: neg

Geophone V3: neg

Geophone H1: pos

Geophone H2: pos

Geophone H3: pos

 

After this measurement, we changed the sign of damping filters of geophone V1,2,3 as second attached figure.