Chapter 2. Introduction

The Flute instrument is a triaxial, very broadband, force-feedback seismometer in a 64mm diameter by 1m borehole package. The instrument can be field-configured to one of four pre-set frequency responses.

The instrument is capable of self centring when installed at up to 30° from the vertical (60° for the vertical component) and includes a hardware-activated auto-centre function for true autonomy.

Up to five sensors may be connected together in a string configuration with 3 differential analogue velocity channels and 3 analogue mass position (acceleration) outputs at 1200V/ms-2 for each sensor in the string.

The instrument contains a low-power processor which can be used to control the frequency response and to initiate centring (offset-nulling) but it can also be operated in fully autonomous mode: Once power is applied to the system, the sensors will centre themselves with no further input from the user. The processor can be controlled using logic lines or via a serial communication channel. This allows computer-control of additional functions, if required. It can be used, for example, to speed up the installation process by manually applying a centre command.

2.1 Important information