| 摘要 |
A device for detecting the slag level in a molten bath comprises a measurement probe (2) provided on the probe with an antenna (8) for picking up hum in particular mains hum, in the vicinity of the antenna. A hum detector is connected to the antenna (8). Antenna (8) may be an exposed metal rod (as shown) protruding from the end of the probe (2) or it may be constituted by the wires of a temperature measuring thermocouple. The hum detector is arranged to compare the signal picked up by the antenna as it is moved by stepping motor (3) with constant velocity towards molten bath (1) with an alternating voltage related to the mains frequency only at the zero crossings of the alternating voltage. If the antenna signal and alternating voltage correspond with each other during a predetermined number of zero crossings an output is produced indicating mechanical contact of antenna (8) with the slag layer and which causes stepping motor (3) to stop. The number of steps moved is indicative of the slag level. The probe may include an inductor for detecting conventionally slag/metal interface. <IMAGE> |
