Current sensors

Progress in mean of modelisation and inverse problem solving [1] let us hope to dispose soon of these tools for flaws 3D imaging in Non Destructive Control with eddy current sensors. This will achieve a real improvement of the actual methods, mainly based upon signature analysis. But the actual eddy current probes used for steam generators tubes inspection in nuclear industry do not produce the adequate measurements and/or are not modelisable. 

D. Miller, D.Placko "Pre-processing of signals delivered by a new eddy current sensor for non ferromagnetic tubes testing" in IMTC 96... 

FIG. 29-8 Typical high-voltage ac motor starter illiistrating several protective schemes fuses, overload relays, ground-fault relays, and differential relays with the associated current transformer that act as fault-current sensors. In practice, the differential protection current transformers are located at the motor, hut the relays are part of the starter. 

The advent of new, more reliable, and sensitive vibration instrumentation such as the eddy-current sensor and the accelerometer coupled with modern... 

Current sensors Magnetoresistive Sensors Thin Film, MST P... 

To give an example both sensitivity coefficients are evaluated for the current sensor (see Sect. 10.3 for details). For the bulk detection of glucose this results in A bulk (rad) = 5.6 x 102 AC (g/ml), whereas for the adsorption of proteins on the sensor surface the overall sensitivity of the sensor is evaluated as A< >layer (rad) = 2.0 x 10 5 Am/A (fg/mm2). Measuring the phase change A< >,-, between any of the two channels i and j can thus give an estimation on the change in analyte concentrations between those two channels. If one channel (e.g., channel N) is used as a reference channel, then ACV = 0 and AmN = 0 and absolute analyte concentrations can be determined. 

T H ) Temperature switch ( P L ) Pressure switch ( PSH ) Pressure switch (jsT) Flow switch ( MP Motor protection switch (PT100 Temperature sensor For DRYVAC with LIMS ( C Current sensor ( EPS ) Exhaust pressure sensor... 

E. Baum, Some Considerations for Inductive Current Sensors, Sensor and Simulation Note 59... 

Fig. 7.19 High temperature limiting current sensor (a) pinhole version and (b) porous diffii-sional barrier version...

The y-axis of the ROC curve shows the rate of true positives (related to sensitivity), whereas the x-axis shows the rate of false positives (1 - specificity). A poor sensor response will lie along the diagonal. An ideal sensor performance curve lies on the y-axis, that is, zero rate of false positives and high sensitivity. However, the performance of most current sensors lies between the y-axis and the y = x diagonal line as shown in Fig. 3. 

The classic solution is the application of current and voltage transformers, usually as a cast resin embedded type. As a certain disadvantage of inductive transducers, their small frequency range may be considered. Other solutions for current sensors are Rogowski coils (with active or passive integrators) or the fibre-optic current sensor, based upon the Faraday effect [20]. 

Figure 6.69 gives an example for an optical current sensor. The light path is wound around a current-carrying conductor equidirectionally with the azimuthal magnetic field of the current. The rotation of the plane of the electric vector is not detectable on its own and is converted to light intensity variations by a polarizer/analyser combination. A photo diode is used as a light intensity detector. The optical sensor itself is installed in the - e - compartment, the electronics shall be protected in an adequate type of protection, e.g. in a small flameproof - d - enclosure or in encapsulation - m -. In the special case of an energy distribution system with combined - e - and - d - compartments, the optical fibres may enter the d-compartment to the electronics inside via bushings complying with d -standards EN 50018 or IEC 60079-1 respectively (Fig. 6.70). The evacuation of the sensors into the e-compart-ment results in additional available space in the more expensive d-compart-ment, compared with increased safety - e -. ...

In conventional CMP, end-point detection relies on in situ sensors such as eddy current sensors [26] to measure the remaining copper film thickness. In... 

---