High accuracy method for measurement of vibrating wire transducer

Abstract

The vibrating wire transducers have been in use for many years in building monitoring process. Vibrating wire transducers have a reputation for long-term stability. For measuring, the transducer is excited with a sweep excitation signal [3]. The output is an alternating signal whose frequency is fixed by physical parameter. The new generations of vibrating wire transducers have the output signal frequency in the 1.8 kHz - 2.5 kHz range [4]. The accuracy of physical parameter is of 0.05 % of full scale. This paper is focused on a measurement system that uses an 8-bit microcontroller as a central unit. The problem appears in the measurement of output signal. For results more accurate than 0.05 %, the clock frequency of the counter unit needs to be higher of 25 MHz. But usually, the 8-bit microcontrollers family have the clock frequency in the 1 MHz - 16 MHz range. To improve the results the output signal needs to be measured in the damped oscillating area and, over acquired data a statistical analyze is applied. The damped oscillating area is experimentally established because this time the interval depends on the transducers internal components, like mutual inductivity, coupling capacities, these are unknown.