Tube blockage monitor

Apparatus for detecting a blockage in flow of particles through a duct comprising:

• a sensor for mounting on a wall of the duct;
• the sensor having a light source for projecting light from the light source into the interior of the duct;
• the sensor having a light receptor arranged to produce an output signal proportional to the intensity of light received such that the output signal varies as a particle passes the sensor;
• the sensor having a monitoring circuit responsive to the output signal to generate therefrom an output including a series of pulses representative of the passage of any particles;
• a blockage module for receiving the output and for determining from the output whether there is a blockage of the duct sufficient to interfere with the flow of particles and to generate a warning signal in the event that a blockage is detected;
• wherein the blockage module is spaced from the sensor and wherein a power voltage is supplied to the sensor using two wires only and the output including the series of pulses is communicated along the same two wires;
• wherein the monitoring circuit includes a comparator circuit for detecting when a change in the output signal exceeds a predetermined threshold and a communication circuit operable by the comparator circuit to generate a current pulse transmitted along the two wires detectable by the blockage module;
• wherein the light source includes a power supply which receives a power voltage from the blockage module along the connecting wires;
• wherein the blockage module is arranged to effect a test of the sensor by communicating to the sensor a pulse in the power voltage;
• wherein the sensor is arranged so as to generate a corresponding but delayed pulse in the light from the light source;
• and wherein the monitoring generates the corresponding delayed current pulse such that the current pulse is detectable by the blockage module separately from the pulse in the power voltage.

Apparatus for detecting a blockage in flow of particles through a duct comprising:

• a sensor for mounting on a wall of the duct;
• the sensor having a receptor arranged to produce an output including a series of pulses representative of the passage of any particles;
• a blockage module for receiving the output and for determining from the output whether there is a blockage of the duct sufficient to interfere with the flow of particles and to generate a warning signal in the event that a blockage is detected;
• the blockage module including a processor providing a counter for counting the number of pulses in a predetermined time period and the processor containing algorithmic elements using which it can be determined from the counted number whether there is a blockage;
• a ground speed indicator for providing a speed input indicative of a ground speed of movement of the duct across ground onto which the particles are to be applied;
• and a communication system for communicating the speed input to the processor of the blockage module;
• the processor being arranged to modify the algorithmic elements in response to a change in the ground speed input received from the communication system;
• wherein there is provided a monitoring circuit at the sensor;
• wherein the blockage module is spaced from the sensor;
• and wherein a power voltage is supplied to the sensor using two wires only and the output including the series of pulses is communicated along the same two wires.

Apparatus for detecting a blockage in flow of particles through a duct comprising:

• a sensor for mounting on a wall of the duct;
• the sensor having a receptor arranged to produce an output including a series of pulses representative of the passage of any particles;
• a blockage module for receiving the output and for determining from the output whether there is a blockage of the duct sufficient to interfere with the flow of particles and to generate a warning signal in the event that a blockage is detected;
• the blockage module including a processor providing a counter for counting the number of pulses in a predetermined time period and the processor containing algorithmic elements using which it can be determined from the counted number whether there is a blockage;
• an application rate indicator for providing an application rate indicative of an intended rate of application of the particles to the ground onto which the particles are to be applied;
• and a communication system arranged for communicating the application rate to the processor of the blockage module;
• the processor being arranged to modify the algorithmic elements in response to a change in intended application rate received from the communications system;
• wherein there is provided a ground speed indicator for providing a speed input indicative of a ground speed of movement of the duct across ground onto which the particles are to be applied and a communication system for communicating the speed input to the processor of the blockage module, and wherein the processor is arranged to modify the algorithmic elements in response to the ground speed input received from the communication system.