Chapter 5. Sensor Configuration
To change the auto-lock and auto-centre default configurations, it is necessary to connect directly to the sensor's serial port.
Note: The serial connection is is not available from the lid of a digital sensor: gaining access will require the removal of the lid.
5.1 Connection
Connection methods differ between analogue and digital sensors. Consult the relevant section below for details.
5.1.1 Connecting to analogue-output sensors
In the case of the analogue sensor, a standard 3T breakout box and cable are required, along with a special terminal cable (the connections of which are shown in section 6).
Connect the sensor to the breakout box and power it up as normal. Using the special serial cable, connect the recorder connection of the breakout box to a serial port on your computer.
Run a terminal emulation program (such as minicom for Linux or PuTTY for Windows) and set the serial port to 9,600 baud, 8 data bits, 1 stop bit, no parity, and no hardware or software flow control.
You should then see a sign on message similar to the one below:
*************************
Guralp SOH MKIV v1.01 CEP
*************************
Temperature = 21 Deg C
Normal
Auto Centre = Enabled
Threshold = 1000
Trigger average = 10
V Mass: Locked Gate: OK
N Mass: Unknown Base: Up
E Mass: Unknown Base: Up
V: Locked N: Locked E: Locked
status = 2
U:unlock, L:lock, C:centre
?
See section 5.2 for configuration details.
5.1.2 Connecting to digital-output sensors
In the case of the digital sensor, the equipment required is a standard 3T breakout box, a cable to connect directly to the PSU/SOH board internally (contact GSL for this cable), and a special terminal cable (the connections of which are shown in section 6).
Remove the lid of the sensor which has the digitizer attached. To do this remove the six M2.5 cap-head screws around the outside of the lid. Remove the pressure relief screw.
Caution: If working at altitude, there may be a considerable pressure differential between the inside of the instrument and the atmosphere. Be careful that the pressure-release screw does not fly off, potentially causing injury.
Carefully pull the lid out of the tube. Remove the ribbon-cable connection to the sensor and put the lid to one side.
Connect from the 26 way connector on the PSU/SOH board to the breakout box and power it up as normal for an analogue sensor. Using the special serial cable, connect the recorder connection of the breakout box to a serial port on your computer.
Run a terminal emulation program (such as minicom for Linux or PuTTY for Windows) and set the serial port to 9,600 baud, 8 data bits, 1 stop bit, no parity, and no hardware or software flow control.
You should then see the sign on message similar to the one below.
*************************
Guralp SOH MKIV v1.01 CEP
*************************
Temperature = 21 Deg C
Normal
Auto Centre = Enabled
Threshold = 1000
Trigger average = 10
V Mass: Locked Gate: OK
N Mass: Unknown Base: Up
E Mass: Unknown Base: Up
V: Locked N: Locked E: Locked
status = 2
U:unlock, L:lock, C:centre
?
See section 5.2 for configuration details.
5.2 Configuration of functions
The parameters of the auto-centre and auto-lock functions are set as part of the process of enabling each function. To change these parameters when the functions are already enabled, first disable them and then re-enable them: you will be prompted for new parameters when you re-enable them.
The current state of each function is shown in the sign-on message, along with the current values set for the related parameters. The sign-on message below shows that the auto-centre is enabled and that the threshold and trigger average values are currently set to 1000 and 10 respectively.
*************************
Guralp SOH MKIV v1.01 CEP
*************************
Temperature = 21 Deg C
Normal
Auto Centre = Enabled
Threshold = 1000
Trigger average = 10
V Mass: Locked Gate: OK
N Mass: Unknown Base: Up
E Mass: Unknown Base: Up
V: Locked N: Locked E: Locked
status = 2
U:unlock, L:lock, C:centre
?
5.2.1 Changing the auto-centre values
If the auto-centre function is enabled, disable it by typing 
. The system will respond with the sign-on message; note that the auto-centre parameters are now missing, as shown below:
*************************
Guralp SOH MKIV v1.01 CEP
*************************
Temperature = 21 Deg C
Normal
V Mass: Locked Gate: OK
N Mass: Unknown Base: Up
E Mass: Unknown Base: Up
V: Locked N: Locked E: Locked
status = 4
U:unlock, L:lock, C:centre
?
Typing
again will re-enable auto-centring and prompt you to enter new parameters. The system will ask if you want to continue: respond by typing 
:
Continue (Y/N) ? y
A message is printed informing you that auto-centring is enabled.
The SOH will ask for values for the Threshold and Trigger average:
The Threshold is the level, in counts, that the mass position must exceed in order to trigger a centring operation. The counts relate to the output of an internal analogue-to-digital converter, the full scale output of which is 2048.
the Trigger average is the period of time that the mass position must continuously exceed the Threshold before a centring operation is initiated.
The current values of each of these parameters are printed in brackets before the prompts: to retain a current value, key Enter without typing a new value.
Below is an example input:
Auto centre is enabled
Trigger threshold (counts)
Enter Value 1-2048 (1000): 1500
Trigger average (minutes)
Enter Value 1-2000 (10): 15
5.2.2 Changing the auto-lock values
If the auto-lock function is enabled, disable it by typing 
. The system will respond with the sign-on message; note that the auto-lock parameters are now missing, as shown below:
*************************
Guralp SOH MKIV v1.01 CEP
*************************
Temperature = 21 Deg C
Normal
V Mass: Locked Gate: OK
N Mass: Unknown Base: Up
E Mass: Unknown Base: Up
V: Locked N: Locked E: Locked
status = 4
U:unlock, L:lock, C:centre
?
Typing
again will re-enable auto-locking and prompt you to enter new parameters. The system will ask if you want to continue: respond by typing
:
Continue (Y/N) ? y
A message is printed informing you that auto-locking is enabled.
The SOH will ask for a value for the auto-lock delay. This is the desired time, in seconds, between the detection of a power failure and the initiation of an auto-lock operation.
The current value of this parameter is printed in brackets before the prompt: to retain the current value, key Enter without typing a new value.
Below is an example input:
Auto lock is enabled
Delay for autolock (seconds)
Enter Value 1-1000 (30): 50