Guralp Systems CMG-CD24 - Manual (Page 85)

Operator's Guide
Field Value
components, separated by commas. For velocity
sensors, the gain, or sensitivity, is given on the
sensor calibration sheet in V/ms -1 . The gain of
an accelerometer is expressed on its calibration
sheet in V/ms -2 . Because the outputs are
differential, these are written as “2 × single-
ended-sensitivity”. Most set-ups (including all
those using DM24mk3 and CD24 digitisers) will
use the doubled value, but older integrated
instruments combining a DM24mk2 with a
sensor will use only the single ended sensitivity
value.
COILCONST The coil constant for the Z, N/S and E/W sensor
components, in A/ms
-2 , separated by commas.
These are given on the sensor calibration sheet.
For a CMG-5T accelerometer, the values are all
set to unity; use COILCONST=1,1,1 for these.
CALRES The value of the calibration resistor, in Ω, as
given on the sensor calibration sheet. For a
CMG-5T, use CALRES=1.
CALVPC The sensitivity of the digitiser's calibration
channel, in V per count, as given on the
μ
digitiser calibration sheet. Older CMG-5TD
instruments do not have calibration input
facilities, and thus CALVPC can be omitted.
GRAVITY The local acceleration due to gravity at the
installation site, in ms -2 . This field is used by
Scream! to display streams in physical units. By
default, a standard average g value of 9.80665
ms
-2 is used, but this field can be changed for
greater accuracy if desired.
TYPE
[optional] The model number of the instrument, used for
display purposes.
RESPONSE A string describing the theoretical response of
the instrument, in the form response-type unit.
See the table below for the correct values.
7.1.2 Response codes and units
Instrument description Response type Unit
CMG-3T (30s–50Hz) CMG­3_30S_50HZ Vel
CMG-3T (60s–50Hz) CMG­3_60S_50HZ Vel
CMG-3T (100s–50Hz) CMG­3_100S_50HZ Vel
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