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Probes for Remote Field
Testing of Heat
Exchangers: Configurations and Capabilities
Figure 1-4
Figure 1 - A basic remote field testing probe. The arrows show the flow of magnetic field from the exciter coil to the detector coil. The direction of flow is normal to the actual lines of magnetic field.
Figure 2 - Common detector configurations. The arrows indicate how the absolute and differential bobbin coils can be split into arrays of smaller coils for greater sensitivity
Figure 3 - Near a tube support plate, the basic two coil remote field testing probe has a shadow (gray area) that is not examined by the detector coil: (a) probe approaches tube support plate; (b) detector has scanned to edge of tube support plate; (c) due to tube support plate, no field is reaching detector (gray zone will not be scanned by detector); (d) exciter detector coupling is resumed (gray zone will be scanned by exciter only).
Figure 4 - Probes: (a) with the basic remote field testing probe, a tube support plate interrupts the field traveling from exciter to detector; (b) the double exciter probe always has at least one exciter transmitter to the detector coil; (c) the double detector probe always has at least one detector receiving the exciter signal. The double exciter and double detector probes do not have a shadow next to the tube plate like the probe in Figure 3.
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