External 1D Sensor - Gecko Compact Product User Manual

An new setting introduced in firmware version 4.1 allows manual control of a high pass filter
on the sensor input. This enables a simple circuit that removes the DC offset from sensors
by introducing a low order high pass frequency filter. For most sensors, it is best to leave
this Input setting as "DC Offset", but if you are using an IEPE sensor or have a sensor that
has a large DC offset, set the Input to "Filtered" to enable the filter which will slowly bring
the signal level down to zero. Do not enable this for long period or broadband
seismometers.
An example of where this Input Filter is important is with the White Industrial Geophones,
which have a signal output between 0V to +5V, where the zero level normally sits at +2.5V.
In this case, much of the -20V to +20V input range of the Gecko is wasted. Running the
Gecko's Input Amplifier at x4 would effectively stretch the 0-5V to 0-20V, but you would
still only be using the upper half of the Gecko's dynamic range. By enabling the Input Filter,
the zero level of 2.5V would be brought down to 0V, so the output signal would be -2.5V to
+2.5V. This allows you to use an Input Amplifier setting of x8 to stretch the sensor's output
from -20V to +20V, using the full dynamic range of the Gecko's 24-bit resolution.
Sensor Serial No.
A 20-character field is available to record your sensor's serial number. This information is
stored in the station status text file for future reference. Upper and lower case letters,
numbers, and some special characters are available.
Mass Lock & Unlock
Guralp 3-series seismometers have motorised mass controllers that allow the delicate
sensor components to be locked in place for transport and unlocked after installation. Use
Sensor Lock before moving a sensor (this takes just a few seconds), or Sensor Unlock
when the sensor is in place and ready to start monitoring, or to re-centre the masses.
Issuing this command simply connects one of two pins on the sensor connector to Ground
for 5 seconds, so the feature could be used for other purposes if required.

External 1D Sensor

If you have a 4-channel Gecko Compact, Rugged, Blast or SMA, you can set up your 1D
sensor in a similar way to the 3D sensor. Simply select a sensor from the list and optionally
re-enter the menu to customise its name, units and sensitivity. No other settings are
available for this channel.
Set the sensor serial number using the only other menu option.
The SIG+, SIG- & Input settings of the 1D sensor are the same as set for the 3D sensor.
1D Sensor
Sensor Name
> Type: Pressure
Sensitivity
13