The SmartBob II uses a heavy-duty direct drive motor with electronic torque control to provide maximum pull strength throughout the entire measurement cycle. The shaft of the motor is connected directly a supply pulley in the mechanical cavity of the housing. When the SmartBob II remote located at the top of the silo is asked to take a measurement, the motor releases a strong Stainless Steel aircraft cable from the supply pulley and a weight sensor probe descends to the surface of the material. During the decent, the SmartBob II remote measures the cable dispensed. A microcontroller counts the pulses from an internal encoder that produces 80 pulses per foot. When the sensor probe touches the material surface, measurement information is transmitted and pulse generation is momentarily stopped. The absences of these pulses immediately cause the motor to reverse and retract the sensor probe. Should the sensor probe ever slide down an angle of repose in an active vessel or sink in light material, a special mechanical brake on the back of a spring loaded idler arm will release and brake the slotted timing pulley, instantly stopping it. The timing pulley is what generates the pulses and when stopped, reverses the motor to retract the sensor probe. An electronic control reduces the motor torque during the last 6" of the retract cycle and the pulses again stop when the probe makes soft contact with the flange that then seals the unit, alerting the microcontroller to shut-down the motor. The retract distance is also measured and compared to the descend measurement to assure the sensor probe has fully retracted.

Competitive manufacturers of "Bob" type systems have not incorporated a braking system in their design. The presumption is their units are sensitive enough to stop when they reach and touch the material surface. The flaw in this design is that during a fill or load-out cycle material is constantly moving and the sensor probe may slide with the material. While the sensor probe is sliding (or sinking) there is enough weight pulling on the cable to turn the timing pulley and generate pulses. Since there are pulses, the motor continues to let out cable. This can cause inaccurate measurements or may bury the sensor probe in the material. The fact is this design has not eliminated the real problems that are inherent with most cable based systems.

We Cure the Problem -- Not Treat the Symptoms.

The BinMaster SmartBob II has been designed to keep the sensor probe from taking inaccurate measurements, sinking through material, or from hanging up in the vessel:

• The Tension Arm Assembly Brake stops the sensor probe from sliding down the angle of repose, or sinking in light density material
• The motor shut-off is delayed so it will continue to pull if force is placed on the sensor probe during the retract phase. It also continues to pull the probe if it is momentarily thrown around by turbulence in the vessel
• If material or an object strikes the sensor probe hard enough to stop it while retracting, it will hold for 2 seconds and try to pull up automatically a second time
• Total isolation of the mechanical and electrical cavities assure the electronics remain clean and moisture free
• Four removable brushes wipe the cable clean before entering the mechanical cavity
• Standard air purge on all units to keep all foreign materials out of the mechanical cavity of the unit