A Resistive Probe for Continuous Measurement of Electroconductive Liquid
Level faced to Electromagnetic Fields
We study the experimental device shown on figure 1.
Figure 1 : view of the experimental device
A rectangular tank containing a liquid metal is put in an alternating electromagnetic field generated by an inductor. When the frequency of the current increases, the irrotational part of the induced electromagnetic forces acts on the shape of the meniscus by repulsion forces. Thanks to the efforts made in research on cold crucibles and ladle furnaces, this phenomenon was well studied in an axisymmetric configuration.
We intend to measure the electromagnetic shaping h = h(x,y,t) of a mercury free surface in a rectangular configuration (x, y are the horizontal co-ordinates and t is the time).To this aim, we developed a specific probe which measures h continuously at a fixed point. This is a resistive probe, connected to a Wheastone bridge. It was designed so as to :
- be insensitive to the perturbations of the electromagnetic environment,
- allow parallel multiple measurements,
- be insensitive to the dirtying due to the presence of mercury.
The probe and its electronic wiring are described below. The resistive wire is
short-cutted by the mercury. Then its resistivity and the electronic signal vary with the height h.
A calibration of the probe is performed to find the law 
.
Figure 2 : Principle and wiring of the level probe