The EMLI III Suspended Sensor mold level measurement system consists of a state-of-the-art electronics packaged combined with a custom designed and steel mill proven electromagnetic metal level sensor.  The sensor is mounted on a removable arm that is positioned in such a manner that the actual sensor head is suspended over the liquid metal pool.  The sensor arms can be manually operated or automated.

This arrangement allows for the easy removal and insertion of the sensor, even during casting.

The EMLI III suspended sensor is basically a balanced coil that is suspended over the liquid pool of metal.  The proprietary coil design is such that the measurement area is concentrated to a narrow area below the sensor.  This design minimizes the influence of materials above the sensor and the influence of the mold side walls.

The sensor consists of three coils, one transmitter coil and two receiver coils.  An excitation signal from the EMLI™ electronic unit is applied to the transmitter coil.  The receiver coils are connected in such a manner that when there is no metal present in the sensors measurement field,  the output of the sensor  is approximately zero.  This is considered to be the 'balanced' condition.  

When metal in introduced into the sensor's measurement field, the metal has a greater effect on one of the receiver coils than on the other.  This causes an output from the sensor and the sensor is said to be 'unbalanced'.

This effect is used by the EMLI™ electronic unit to generate a signal that is proportional to the level of metal in the mold.

The EMLI III mold level measurement system with cassette sensors consists of two sensors, a transmitter sensor and a receiver sensor, that are mounted directly to the top of one of the mold's copper broad faces. 

The a regulated AC current is sent through the transmitter sensor.  This current causes the transmitter to generate a magnetic field.  This magnetic field induces eddy currents in the surface of the adjacent copper mold wall.  The eddy currents product their own electromagnetic field which is detected by the receiver sensor.

When the metal level in the mold is low, more of the copper wall is exposed and more eddy currents are generated resulting in a larger magnetic field and a stronger received signal

When the metal level in the mold is high, the copper is shielded by the liquid metal and the amount of eddy currents produced is diminished.  This results in a smaller magnetic field and a weaker received signal.