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AC Potential Drop Technique
Study depth propagation and avoid mechanical fracturing
The Crack Depth Gauge RMG 4015 from our principal company M/s KARL DEUTSCH GmbH, Germany measures crack depths on workpieces of iron, ferrous, austenitic steels etc and can also be used for determing crack depths in copper, brass, aluminum and other non-ferrous metals.
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| Model RMG 4015 | ||
It operates due to the potential probe principle: A probe with four spring-loaded and gilded contact pins is positioned across the crack to be measured on the workpiece. A constant alternating current is passed via two of the pins into the workpiece; the two other pins measure the voltage drop across the crack, where the crack depth is derived from. The instrument utilizes the skin effect, which forces the current flow to the surface of the conductor and therefore follows the contour of the crack. A calibration block with an artificial crack with a crack depth starting from zero up to 10mm is provided with the RMG 4015. Therefore, the user can check the instrument and probe calibration during the tests. The conversion of the measured voltages into crack depths is done by the microprocessor which controls the RMG 4015. Factory-set calibration tables material wise, are stored in the instrument for this purpose. Prior to a measurement, the probe is placed on a crack-free spot of the workpiece. The measured voltage is compared with the stored values of the calibration table. The individual characteristics of the material are found and used by the microprocessor to determine the exact crack depth in the subsequent measurement. Optimum reproducibility of the measurements (+/- 0.1 mm for 100mm crack depth) are obtained. Even steels with low or no permeability (e.g. Austenites) or non-ferrous metals of higher electrical conductivity (e.g. Aluminium or brass), which are more difficult to test, can be measured with good accuracy levels.
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| Straight crack depth measurement |
Inclined crack depth measurement |
Special probes for special tasks |
A wide range of probes are offered alongwith the instrument. Specific to some special applications, also special probes have been developed to suit the task.