EXTENDED OVERFLOW INDICATION FOR HIGH DYNAMIC RANGE ULTRASONIC FAULT DETECTION SYSTEMS

• US 20100147081A1
• Filed: 02/25/2010
• Published: 06/17/2010
• Est. Priority Date: 10/14/2005
• Status: Active Grant

• Current Assignee: Olympus Ndt
• Original Assignee: Olympus Ndt
• Inventors: Thomas, Andrew
• Granted Patent: US 8,490,491 B2
• Time in Patent Office: Days
• US Class Current: 73/627
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 29/043 in the interior, e.g. by shear waves
• CPC Class Codes: G01N 29/262 by electronic orientation or focusing, e.g. with phased arrays phased arrays per se G10K11/34
• CPC Class Codes: G01N 29/42 by frequency filtering or by tuning to resonant frequency
• CPC Class Codes: G01N 29/44 Processing the detected response signal , e.g. electronic circuits specially adapted therefor digital signal processing per se G06F17/00
• CPC Class Codes: G01N 29/4463 Signal correction, e.g. distance amplitude correction [DAC], distance gain size [DGS], noise filtering
• CPC Class Codes: H03M 1/188 Multi-path, i.e. having a separate analogue/digital converter for each possible range

Abstract

A method and apparatus for effecting ultrasonic flaw detection of an object processes an echo signal received from the object being tested in at least three signal channels, wherein the echo signal is scaled to different degrees along each channel to increase and extend the dynamic range of an associated A/D converter system, in a manner which dispenses with the need for using numerous analog high pass and low pass filters and a variable gain amplifier. This reduces complexity and avoids performance limitations. The digital to analog converters sample the differently scaled input signal and a selection circuit selects the output of the digital output obtained from that analog to digital converter which has the highest gain, but which has not overflowed. The digital outputs are seamlessly merged to produce an output that can be displayed as a scan display which shows the location of faults.

Claims

1. An inspection device configured for inspecting a test object, comprising:

a probe unit configured to excite the test object to produce a wave response, to receive the wave response and to produce from the wave response one or more corresponding electric echo signals;

a receiver having one or more signal processing channel, each channel configured to scale the echo signal to a different degree and to produce one or more corresponding scaled signals,

one or more overflow indicators providing overflow indications for the processing channel,

one or more analog to digital converters configured to digitize the scaled signals and to produce therefrom corresponding digitized signal samples;

a digital memory for storing the digitized signal samples; and

a channel selection element configured to select the signal samples that provide the largest amplification without having overflowed;

wherein said overflow indicators are configured to provide overflow indications associated with a predetermined number of signal sample points proceeding to and/or succeeding a sample point that is overflowed.

2. The device of claim 1, further including at least one delay element for delaying outputting of the digitized signal samples to provide each respective overflow indicator with a delay of at least one sample point, to respond prior to the signal samples being selected.

3. The device of claim 2, wherein in each of said signal processing channels, the overflow indicator and the corresponding delayed overflow signal samples are provided using an OR function.

4. The device of claim 3, wherein the device is configured such that the overflow indicator can be:

a) turned on without delay so that it will occur prior to the time when the delayed analog to digital converter output signal sample is selected by the selection element, and b) turned off with delay in order to be synchronized with the delayed signal sample that is selected by the selection circuit after an overflow condition has passed.

5. The device of claim 1, further including a delay element configured to add one or more sample points to the overflow indicator.

6. The device of claim 5, further including a circuit configured to apply an OR function between the overflow indicator and the delay element.

7. The device of claim 1, further including a comparator to compare adjacent processing channels, to detect when a given analog to digital converter is out of a sever saturation.

8. An object inspection system, comprising:

a transmit and receive section to generate a test signal and to receive a responsive echo signal;

a transducer that converts the test signal to an ultrasonic signal, applies the ultrasonic signal to a target object to be tested, receives an ultrasonic echo signal and produces the echo signal for the transmit and receive section;

a signal processing circuit coupled with the transmit and receive section for receiving and processing the echo signal, the signal processing circuit including at least two signal processing channels, each channel scaling the echo signal to a different degree, and each channel having a respective analog to digital converter;

a selection circuit which selects that output of that analog to digital converter which provides the largest amplification of the echo signal without having overflowed; and

a delay circuit for delaying outputs of at least one of the analog to digital converters to allow the analog to digital converters to respond to a leading edge of a fast slewing input signal, prior to processing of said outputs at said selection circuit.

9. The device of claim 8, wherein the delay circuit provides a delay which is a multiple of a clock period associated with the system.

10. The device of claim 9, wherein the delay circuit is further effective to delay a respective overflow output of the analog to digital converters.

11. An object inspection system, comprising:

a transmit and receive section to generate a test signal and to receive a responsive echo signal;

a transducer that converts the test signal to an ultrasonic signal, applies the ultrasonic signal to a target object to be tested, receives an ultrasonic echo signal and produces the echo signal for the transmit and receive section;

a signal processing circuit coupled with the transmit and receive section for receiving and processing the echo signal, the signal processing circuit including at least two signal processing channels, each channel scaling the echo signal to a different degree, and each channel having a respective analog to digital converter;

a selection circuit which selects that output of that analog to digital converter which provides the largest amplification of the echo signal without having overflowed; and

a delay circuit which is effective to cause the selection circuit to refrain from selecting an analog to digital converter output which has overflowed, until after the overflowed analog to digital converter has recovered from a saturation condition.