User's Guide

CHAPTER 1. OVERVIEW 4
a frequency range of 200-6000Hz and can be stimulated using a
swept sine wave of 6V peak to peak.
It has been successfully used with a variety of sensor models,
including:
• Soil Instruments W9 Piezometer
• Soil Instruments ST1 Spot Weldable Strain Gauge
• Soil Instruments ST2 Arc Weldable Strain Gauge
• Soil Instruments ST4 Embedment Strain Gauge
• Geokon 4500S Piezometer
Contact your technical sales representative for more informa-
tion.
1.2.3 Sensor Node Selection
The first thing to consider is the type of sensor to be attached. Most
vibrating wire sensors (piezometers, extensometers, inclinometers,
etc.) contain a single vibrating wire, coil, and temperature sensor.
Some larger sensors may contain a number of vibrating wire-coil
pairs (typically large load cells containing three, four or six wires),
but only a single temperature sensor.
The FM3N-VW17 is the best choice for sensors containg multiple
vibrating wires, as it has one connector which supports up to seven
vibrating wires with a single temperature sensor.
For simple, single-wire sensors, the only thing to be considered
is the number of devices which are to be co-located. The FM3N-
VW11, FM3N-VW41 and FM3N-VW81 are designed to support up to
one, four or eight sensors respectively.
Often a FM3N-VW11 is used for small load cells, or at the top
of a bore hole with a single piezometer. The FM3N-VW41 is typi-
cally used for strain monitoring on props where three or four strain
gauges are mounted around a prop in close proximity to each other.
It can also be used at the top of boreholes where a number of
piezometers or other down bore hole sensors are mounted down
the same tube. The FM3N-VW81 is also often used at the top of
boreholes where a number of piezometers or other down bore hole
sensors are installed.