Calibration and balance system in pulse eddy current testing apparatus

Claim 2

In pulse eddy current testing apparatus including test pulse generating means, test coil means having primary winding means supplied with driving pulses from said test pulse generating means and secondary winding means for producing output signals varying with defects or flaws in objects under test, an input transformer connected with said secondary winding means and in turn connected with a tuned amplifier for amplifying said output signals, a pair of phase-sensitive detectors supplied with quadrature gating signals and with the output of said tuned amplifier for producing quadrature signal components therefrom, and display means supplied from said phase-sensitive detectors for indicating the amplitude and phase of signals supplied thereto, calibration check apparatus which comprises a. a low frequency pulse source having a PRF low compared to the PRF of said test pulse generating means, b. a calibrate transformer having a primary in series with the primary winding means of said test coil means, c. a calibrate generator for receiving the outputs of said calibrate transformer and low frequency pulse source to produce a modulated calibration check signal, d. and switchable means for switching said test apparatus alternatively to test and calibration check conditions, e. said switchable means in the test condition thereof enabling said test apparatus for detecting defects or flaws in objects under test and inhibiting the supply of said modulated calibration check signal to said test apparatus, f. said switchable means in the calibration check condition thereof including means for connecting a low impedance across said primary winding means of the test coil means, disconnecting said secondary winding means from said input transformer, and supplying said modulated calibration check signal to said input transformer to thereby produce a calibration check indication on said display means.

Claim 3

Apparatus according to claim 1 in which the input impedance of said calibrate transformer is small compared to the input impedance of said test coil means.

Claim 4

Apparatus according to claim 2 in which said display means is a cathode-ray oscilloscope.

Claim 5

In pulse eddy current testing apparatus including test pulse generating means, test coil means having primary winding means supplied with driving pulses from said test pulse generating means and a plurality of secondary windings for producing output signals varying with defects or flaws in objects under test, said secondary windings being connected in series opposition with respect to voltages induced therein from said primary winding means, an input transformer connected with said secondary windings and in turn connected with a tuned amplifier for amplifying said output signals, a pair of phase-sensitive detectors supplied With quadrature gating signals and with the output of said tuned amplifier for producing quadrature signal components therefrom, and display means supplied from said phase-sensitive detectors for indicating the amplitude and phase of signals supplied thereto, calibration and balance check apparatus which comprises a. a low frequency pulse source having a PRF low compared to the PRF of said test pulse generating means, b. a calibrate transformer having a primary in series with the primary winding means of said test coil means, c. a calibrate generator for receiving the outputs of said calibrate transformer and low frequency pulse source to produce a modulated calibration check signal, d. a balance generator for connection with said low frequency pulse source and with the output circuit of said tuned amplifier for producing a modulated balance check signal when an unbalance signal occurs in said output circuit, e. and switchable means for switching said test apparatus alternatively to test, calibration and balance check conditions, f. said switchable means in the test condition thereof enabling said test apparatus for detecting defects or flaws in objects under test and inhibiting the supply of said modulated calibration and balance check signals to said test apparatus, g. said switchable means in the calibration check condition thereof including means for connecting a low impedance across said primary winding means of the test coil means, disconnecting said secondary windings thereof from said input transformer, and supplying said modulated calibration check signal to said input transformer to thereby produce a calibration check indication on said display means, h. said switchable means in the balance check condition thereof including means for connecting said secondary windings of the test coil means to said input transformer, enabling said balance generator for producing said modulated balance check signal, and supplying said modulated balance check signal to said phase-sensitive detectors to thereby produce a balance check indication on said display means.

Claim 6

In pulse eddy current testing apparatus including test pulse generating means, test coil means having primary winding means supplied with driving pulses from said test pulse generating means and a plurality of secondary windings for producing output signals varying with defects or flaws in objects under test, said secondary windings being connected in series opposition with respect to voltages induced therein from said primary winding means, an input transformer connected with said secondary windings and in turn connected with a tuned amplifier for amplifying said output signals, a pair of phase-sensitive detectors supplied With quadrature gating signals and with the output of said tuned amplifier for producing quadrature signal components therefrom, and display means supplied from said phase-sensitive detectors for indicating the amplitude and phase of signals supplied thereto, calibration and balance check apparatus which comprises a. a low frequency pulse source having a PRF low compared to the PRF of said test pulse generating means, b. a calibrate transformer having a primary in series with the primary winding means of said test coil means, c. a calibrate generator for receiving the outputs of said calibrate transformer and low frequency pulse source to produce a modulated calibration check signal, d. a balance generator for connection with said low frequency pulse source and with the output circuit of said tuned amplifier for producing a modulated balance check signal when an unbalance signal occurs in said output circuit, e. and switchable means for switching said test apparatus alternatively to test, calibration and balance check conditions, f. said switchable means in the test condition thereof enabling said test apparatus for detecting defects or flaws in objects under test and inhibiting the supply of said modulated calibration and balance check signals to said test apparatus, g. said switchable means in the calibration check condition thereof including means for connecting a low impedance across said primary winding means of the test coil means, disconnecting said secondary windings thereof from said input transformer, and supplying said modulated calibration check signal to said input transformer to thereby produce a calibration check indication on said display means, h. said switchable means in the balance check condition thereof including means for connecting said secondary windings of the test coil means to said input transformer, enabling said balance generator for producing said modulated balance check signal, and supplying said modulated balance check signal to said phase-sensitive detectors to thereby produce a balance check indication on said display means.

Claim 7

Apparatus according to claim 4 in which the input impedance of said calibrate transformer is small compared to the input impedance of said test coil means.

Claim 8

Apparatus according to claim 4 including a resistance attenuator connected between the output of said tuned amplifier and said phase-sensitive detectors, said balance generator including means for alternately connecting and substantially disconnecting a shunt resistance across a portion of said resistance attenuator in response to pulses from said low frequency pulse source.

Claim 9

Apparatus according to claim 6 including means for applying a predetermined A-C voltage across at least a portion of said resistance attenuator, said shunt resistance being adjustable to produce a predetermined indication on said display means for said predetermined A-C voltage.

Claim 10

Apparatus according to claim 7 in which said display means is a cathode-ray oscilloscope.

Claim 11

Apparatus according to claim 8 in which the input impedance of said calibrate transformer is small compared to the input impedance of said test coil means.

Claim 12

In pulse eddy current testing apparatus including test pulse generating means, test coil means supplied with driving pulses from said test pulse generating means for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, an input transformer connected with said test coil means and in turn connected with a tuned amplifier for amplifying said output signals, a pair of phase-sensitive detectors supplied with quadrature gating signals and with the output of said tuned amplifier for producing quadrature signal components therefrom, and display means supplied from said phase-sensitive detectors for indicating the amplitude and phase of signals supplied thereto, calibration check apparatus which comprises a. a low frequency pulsE source having a PRF low compared to the PRF of said test pulse generating means, b. a calibrate transformer having a primary in series with the supply of driving pulses to said test coil means, c. a calibrate generator for receiving the output of said calibrate transformer and low frequency pulse source to produce a modulated calibration check signal, d. and switchable means for switching said test apparatus alternatively to test and calibration check conditions, e. said switchable means in the test condition thereof enabling said test apparatus for detecting defects or flaws in objects under test and inhibiting the supply of said modulated calibration check signal to said test apparatus, f. said switchable means in the calibration check condition thereof including means for substantially eliminating the flow of driving pulses to said test coil means and establishing a conductive path of low impedance for said pulses, disconnecting said test coil means from said input transformer, and supplying said modulated calibration check signal to said input transformer to thereby produce a calibration check indication on said display means.

Claim 13

In pulse eddy current testing apparatus including test pulse generating means, test coil means supplied with driving pulses from said test pulse generating means for inducing eddy currents in an object under test and producing output signals varying with defects or flaws in the object, an input transformer connected with said test coil means and in turn connected with a tuned amplifier for amplifying said output signals, a pair of phase-sensitive detectors supplied with quadrature gating signals and with the output of said tuned amplifier for producing quadrature signal components therefrom, and display means supplied from said phase-sensitive detectors for indicating the amplitude and phase of signals supplied thereto, calibration check apparatus which comprises a. a low frequency pulsE source having a PRF low compared to the PRF of said test pulse generating means, b. a calibrate transformer having a primary in series with the supply of driving pulses to said test coil means, c. a calibrate generator for receiving the output of said calibrate transformer and low frequency pulse source to produce a modulated calibration check signal, d. and switchable means for switching said test apparatus alternatively to test and calibration check conditions, e. said switchable means in the test condition thereof enabling said test apparatus for detecting defects or flaws in objects under test and inhibiting the supply of said modulated calibration check signal to said test apparatus, f. said switchable means in the calibration check condition thereof including means for substantially eliminating the flow of driving pulses to said test coil means and establishing a conductive path of low impedance for said pulses, disconnecting said test coil means from said input transformer, and supplying said modulated calibration check signal to said input transformer to thereby produce a calibration check indication on said display means.

Claim 14

Apparatus according to claim 10 including a. a balance generator for connection with said low frequency pulse source and with the output circuit of said tuned amplifier for producing a modulated balance check signal when an unbalance signal occurs in said output circuit, b. said switchable means including means for switching said test apparatus alternatively to a balance check condition, c. said switchable means in the balance check condition thereof leaving said test coil means supplied with driving pulses and connected with said input transformer as in the test condition thereof, and including means for enabling said balance generator for producing said modulated balance check signal, and supplying said modulated balance check signal to said phase-sensitive detectors to thereby produce a balance check indication on said display means.