Campbell AVW100 Product Manual

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AVW100 Vibrating Wire Interface 

The AVW100 interface is an active version of the AVW1 Vibrating Wire Interface designed by 

engineers at Slope Indicator of Washington State, USA. The general principles of operation 

are the same as the AVW1/4; please refer to the AVW1/4 manual supplied for general 

information. This document describes the differences between the AVW100 and the AVW1 

and where to find further information on the use of the AVW100 with specific sensors. 

1.  Differences in Specification 

Physically the AVW100 is identical to the AVW1 but electronically it differs in 

that it uses active circuitry, including electronic filters and amplifiers to 

precondition the vibrating wire signal. This allows the use of smaller, lower output 

sensors and sensors which can have a wider range of signal frequencies. The 

specifications on its inputs are: 

•  The minimum detectable signal level is approximately 0.5mV peak to peak 

(250 - 9900Hz), 0.1mV (500 - 5000Hz). (The signal output to the datalogger 

is amplified and conditioned to a +/-2.5V square wave.)  

•  It has an extended frequency range of 250-9900Hz compared to the AVW1. 

•  It has a fixed output drive of 4.8V peak-to-peak. 

Users need to be aware that the high-gain active circuitry results in two other 

functional differences: 

•  The AVW100 consumes approximately 3mA of current continuously which 

may need to be taken into consideration in low-power applications. 

•  The high gain means there is inherent extra sensitivity to noise, particularly 

(but not solely) in the sensing frequency range (the interface can be affected 

by much higher frequencies that have harmonics or which are modulated in 

the sensing frequency range). 

NOTE: The extra noise sensitivity can be an issue in some 

applications. To help avoid such problems, take extra care in the 

screening of both the sensor and the cables to avoid electronic noise 

pickup. If possible, connect the sensor body to a grounding point, 

and consider using cables with individually screened pairs. In 

installations where high frequency noise is causing disturbance to 

the measurements, inductors or specialised signal filters may be 

required to block the noise. 

2.  Differences in Programming 

The AVW100 can be used with exactly the same datalogger instructions as the 

AVW1/4, i.e. instruction P28 or P131 in the CR510, CR10X or CR23X 

dataloggers or the VibratingWire instruction in the CR1000 and CR5000 

dataloggers. Details of both instructions can be found in the relevant datalogger 

manuals and the on-line help in the program editors.