0 Introduction Blast furnace probing equipment, commonly known as a probe, is used in the blast furnace smelting process to detect the material level and height inside the furnace. Accurate detection of the material level and maintaining its stability are crucial for the safe operation and service life of the blast furnace and its top equipment. Our plant's 300m blast furnace probe control has long relied on DC motors and contactors. Due to frequent contactor operation during production, poor contact often occurs, affecting production. Furthermore, DC motors have complex structures, making maintenance inconvenient. Repairing and replacing the probe counterweight involves cumbersome circuit resistance adjustment and debugging, causing inconvenience to maintenance and production. This article will detail the application of PLC-frequency converter control in the 2200m blast furnace probing equipment put into operation in our plant in October 2005. 1. Drive System and Working Principle of the Blast Furnace Probing Equipment The probing equipment consists of a weight chain, wire rope drum, ball valve, gearbox, motor, and control components including a master controller and encoder. During operation, including standby, the chain and wire rope are taut. The speeds are unequal during ascent and descent. When the weight is lowered to track the material surface, to ensure a slow descent and prevent it from burying itself in the material upon impact, thus ensuring inaccurate detection, the motor should generate a torque in the opposite direction, slightly smaller than the weight's torque. This ensures that after the weight touches the material surface, it continues to descend with the surface while the wire rope attached to it remains taut. The master controller controls the probe's extreme positions. The height of the material line is displayed on the operator station screen via an encoder, PLC, and host computer. The probe load is a typical constant torque load. When the probe is lifted, the motor's electromagnetic torque must overcome the load's resistance torque, i.e., the sum of the weight's torque and the system's dynamic friction resistance torque. A certain static friction torque must also be overcome during startup. The direction of the motor's electromagnetic torque is the same as the direction of rotation. The motor is in motor mode, operating in the first quadrant: the probe is lowered by the gravity torque of the weight. To achieve the required accuracy in detecting the material surface, the direction of the motor's electromagnetic torque is opposite to the system's rotation direction; the motor is in reverse braking mode, operating in the fourth quadrant. [b][align=center]For more details, please click: AGSS00 Frequency Converter Applied to Blast Furnace Material Detection Equipment[/align][/b]