Guralp Systems CMG-1T - Manual (Page 28)

CMG-1T Ocean Bottom Seismometer Operator’s
Guide
Section 8, Page 2 September, 1999,
Issue C
18 Sensor Power Return
14 Bowl/SOH Power Return
(also ground for RS232)
13 Transmit Data
32 Receive Data
The seismometer velocity outputs and mass position outputs operate over a
limited range of
±
4.4 Volts. This is due to the fact that the sensor electronics
are operated with
±
5 Volts supply. The output impedance of the analogue
output is set to be 94
Ω
.
The calibration document provides the sensor output responsivity, including the
sensor frequency response.
The sensor analogue electronics power supply voltage can be from 10 to 36
Volts. An isolated dc-dc converter is used to power the sensor analogue
electronics. The power consumption of the system under steady state condition
is 26 milli Amps from 12 Volts (0.32 Watts). This level of power consumption
is achieved without degradation in the sensor performance. However, during
locking, unlocking and centring operations, the power consumption will
increase substantially. To compensate for the large power fluctuations, internal
power management is provided. (The power management unit is under
development, 4th December, 1996.)
The sensor supply is completely separate from the bowl and levelling
electronics. Under normal conditions, the bowl and levelling electronics are
switched off immediately after installation.
The levelling and system status commands are described in the later sections.
In cases where the CMG-1T system is installed within a glass sphere, the sensor
outputs are limited due to the limited number of connector pins. The following
pin assignments must be used for the waterproof glass bowl connector.
1 V+ Vel
2 N+ Vel
3 E+ Vel
4 Sig Gnd
5 +V Sensor
6 0V Sensor/0V
Bowl/RS232 Gnd
7 +V Bowl
8 Tx Data
9 Rx Data