Abstract
Estimation of the output impedance of ultrasonic transducers is required for electrical matching circuits design and for receiving amplifiers noise optimization. This paper presents a simple technique for transducer output impedance estimation using the same data acquisition system and signals that are conventionally used in non-destructive testing. A pair of ultrasonic transducers is used: one for transmission, one for reception. Received signal is recorded under low and high resistance load and transducer output impedance is then obtained from these two signals. Hence, this technique requires only one measurement channel and bias errors are low (no need for calibration). In addition, it is ground referenced and does not require the transducer to be removed from the positioning fixture. Experimental results obtained using different probing signals have been compared against conventional measurements obtained by an impedance analyser.DOI: 10.5755/j01.eie.25.1.22731
Highlights
Ultrasonic techniques offer reliable tools for material integrity or properties evaluation in various fields [1]–[3]
That large RH values reduce the bias error caused by RH deviation (1 %) and that the only influence of RL (1 %) that still remains contributes to a 1 % of the total error bias
The output impedance measurement technique proposed in this paper is simple, requires only one channel and bias errors in the voltage measurement are low
Summary
Ultrasonic techniques offer reliable tools for material integrity or properties evaluation in various fields [1]–[3]. Mismatch of the acoustic impedance between most solid materials and air, together with propagation losses significantly reduces the amplitude of the received signal [8]. Signal losses are even higher, when it is transmitted through test material [9]. A lot of research effort is concentrated on more efficient transducer design [10], [11] and high voltage excitation electronics [12], [13]. Previous research of the reception circuitry was concentrated on two issues: optimization of the input protection circuits [14]–[16] and noise reduction optimization [17], [18]. The case analysed here refers to thru-transmission spectroscopy [7], [9]; where protection circuits are not required.
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