ISO 20339:2017 pdf download – Non-destructive testing — Equipment for eddy current examination — Array probe characteristics and verification.
6 Measurement of electrical and functional characteristics of an array probe 6.1 Electrical characteristics 6.1.1 General The electrical characteristics alone do not define the probe characteristics in its application. The methods and measuring instruments given below are for guidance; other equivalent methods and instrumentation can be used. When characteristics are measured using modelling, this shall be clearly stated. 6.1.2 Measurement conditions Array probes (surface probes and coaxial probes) are in most cases specific to one application. They are delivered with a cable, the design of which depends on the number of elements and which cannot be removed for measurements. The characteristics of the cable are generally proprietary information. The manufacturer provides a cable, the length of which is compatible in terms of resonance and attenuation with the future use of the probe as described by the customer. The following measurements are only applicable to elements consisting of coils. In the case where receiving elements are not coils, specific measurements shall be defined. The measurements are made at the probe connector which is at one end of the connecting cable, without the use of interconnecting elements of the inspection system. The probe is placed in air and away from any conductive or magnetic material. These measurements are only possible if no electronic components (such as amplifiers, multiplexers, etc.) are active in the probe. The measurements are made for each element of the probe accessible at the probe connector. The other elements are left open circuit. When the probe is designed for use under particular conditions, e.g. temperature or pressure, then any additional measurements that are required shall be specified in the application document. 6.1.3 Impedance of coil elements The impedance of all coil elements shall be measured using an impedance meter or impedance analyser as long as the measurement is not prevented by built-in amplifiers. The measured impedance can be given as the values of an equivalent circuit (resistance, inductance and capacitance) or as curve vs. frequency (Bode plot or Nyquist plot). 6.1.4 Impedance of a pattern This measurement is not normally performed by the user as it is not possible once the probe is assembled. It is the manufacturer’s responsibility. — Impedance mode Measure the complex impedance at the central frequency — Separate transmit receive Feed a voltage with the central frequency at the input of the transmitting element and measure the voltage at the output Repeat the measurements on each pattern.
ISO 20339:2017 pdf download – Non-destructive testing — Equipment for eddy current examination — Array probe characteristics and verification
