Novel eddy current speed sensor with axisymmetric coils and solid iron rod as moving part is presented. The analysis is performed both for DC and AC coil currents and for variable iron rod translational speed. The coil inductance and induced voltage results using analytical method and finite element method calculation are compared with measured values. Two different coil configurations are used for simulations and measurement.

A novel transformer-based sensor for a pneumatic cylinder enables measurements of the piston position to be made through a thick conductive cylinder. Unlike existing industrial solutions, which are mainly based on a moving magnet, our se nsors do not require modifications to the parts inside the cylinder. Finite element analysis results are compared with me asurements at various piston positions and excitation fre quencies. Using a suitable model for the magnetic properties of the iron piston bar, we achieved good agreement between the model and reality. When the sensor is operated at 100 Hz, the sensitivity is 200 mV/FS and the raw linearity error is 1.6% of the full 400 mm stroke.

The position of the piston in pneumatic cylinder with aluminum wall can be measured by external inductance sensor without modifications of the aluminum piston and massive iron piston rod. For frequencies below 20 Hz the inductance is increasing with inserting rod due to the rod permeability. This mode has disadvantage of slow response to piston movement and also high temperature sensitivity. At the frequency of 45 Hz the inductance is position independent, as the permeability effect is compensated by the eddy current effect. At higher frequencies eddy current effects in the rod prevail, the inductance is decreasing with inserting rod. In this mode the sensitivity is smaller but the sensor response is fast and temperature stability is better. We show that FEM simulation of this sensor using measured material properties gives accurate results, which is important for the sensor optimization such as designing the winding geometry for the best linearity.

A novel eddy current speed sensor is develope d to measure rotational speed of conductive o bj e ct s. Th e s e nso r co ns ist s o f o n e e xcitation coil and two pick up coils around rotating cylinder or rod. The sensor does not use magnetic y o ke. Fo r t h e a n aly si s a n d e xperimental verification we used 30 mm diameter non-magnetic aluminum and also magnetic solid iron cylinders. The calculated and me asured speed range is until 1200 rpm. 2D analytical method is developed to calculate sensor performance. 2D finite element i s a l so use d for simulations to compare results with 2D analytical method. 3D finite elemen t a n a lys is i s requ ired t o t a k e i nt o a cco u nt significant 3D effects due to the air coils configuration. The experimental results are presented at different steady s t a te s pe eds. Th e calculations results are compared with measurements to validate theoretical models and sensor performance. The eddy current s pe ed se nsor shows high linearity even at low speeds. For ferromagnetic rods we suggest novel double-layer configura t io n: n on-m ag net ic conductive ring or shell on top of the iron rod minimizes the influence of the permeability changes. The main advantage o f t h e n o vel se nsor is that it has neither mechanical nor electrical contact to the rotating rod.

Novel rectangular yokeless current transducer with the range 400 A using 16 microfluxgate sensors around the busbar conductor is presented in this paper. Compared to yokeless transducers utilizing the differential pair of magnetic sensors, our solution has much better suppression of the external currents (lower crosstalk). Compared to industrial transducers with yoke, the new transducer has 15-times lower noise, 7-times better temperature stability, and same crosstalk. Sensor design and design of current monitoring system is presented together with the results of long-term field tests. Crosstalk error is examined in dependence on the number of the operating sensors and external current position.