NDTnet 1998 May, Vol.3 No.5
Analog Characteristics of Ultrasonic Flaw Detectors
Rolf Diederichs *

TABLE OF CONTENTS

Abstract

Background

The Transmitter

Manufacturer's Technical Specification

6.4 Transmitter (EN 12668-1)
The following shall be detailed:
a) shape of transmitter pulse (i.e. square wave, uni-directional or bi-directional) and, where applicable, polarity;
b) at each pulse energy setting and pulse repetition frequency, with the output loaded with a 50 Ohm non-reactive resistor:
1) transmitter pulse voltage (peak-to-peak);
2) pulse rise time;
3) pulse duration (for square wave the range over which the pulse duration can be set);
4) effective output impedance (with tolerance);
5) pulse fall time (for square wave only);
6) pulse reverberation amplitude;
7) frequency spectrum plot.
6.5 Amplifier and attenuator (EN 12668)
The following shall be detailed:
a) characteristics of calibrated attenuator (sometimes called "gain control"), i.e. dB range, step-size, accuracy;
b) characteristics of any uncalibrated variable gain, i.e., dB range;
c) vertical linearity measured with respect to the screen graticule;
d) centre frequency and bandwidth (between -3 dB points) of each band setting (give tolerances). The effect (if any) of the attenuator setting;
e) dead time after transmitter pulse, including the effects of pulse energy damping, attenuator/gain control and frequency band setting;
f) input equivalent noise (µV) at all frequency settings.
g) minimum input voltage for 10 % screen height over all specified frequency ranges.
h) dynamic range of the ultrasonic instrument over all the specified frequency ranges;
i) equivalent input impedance of the ultrasonic instrument over all the specified frequency ranges;
j) details of any distance amplitude correction (DAC) function including the dynamic range, the maximum correction slope (in dB/µs), the form of the correction and the influence of any DAC controls. For instruments with logarithmic amplifiers, see annex A.

The Amplifier

Conclusion

Author

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Copyright © Rolf Diederichs, rd@ndt.net 1. May 1998
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