Electronic control system for a weighing scale

An electronic pneumatic scale system having a trigger mechanism for terminating the flow of material into a scale bucket and means for emptying said scale bucket to repeatedly achieve a predetermined weight of material comprising:

• spring means for mounting said scale bucket;
• an air circuit having an opening aligned with said spring means so that the air pressure in said air circuit is responsive to the position of said spring means and thereby responsive to the weight of said bucket;
• air pressure to voltage transducer means for producing a weight signal corresponding to the weight on said scale bucket;
• latch means for storing and providing a tare signal corresponding to the weight on said scale bucket when it is empty of flowable material;
• first summing means for summing the weight signal and the tare signal to produce a net weight signal;
• an analog to digital converter coupled to said first summing means to convert the net weight signal to a digital net weight signal;
• programmable controller means coupled to said analog to digital converter, said programmable controller means including;
• means for calculating an average weight and a standard deviation for the net weights of the final amount of flowable material measured on said scale bucket after said material stops falling onto said scale bucket, and
• means for producing a computer setpoint signal as a function of the average weight, the standard deviation and the predetermined weight;
• second summing means for receiving and summing the weight signal, the tare signal and the computer setpoint signal to produce an adjusted signal;
• and
• comparator means for comparing said adjusted signal to a predetermined value and for producing a triggering signal to cause the termination of the flow of material upon said adjusted signal becoming equal to said predetermined value.

An electronic pneumatic scale for weighing a flow of material as it accumulates on said scale and for repeatedly triggering the termination of the flow of material to achieve successive weighments of material approximately equal to a predetermined weight comprising:

• air pressure to voltage transducer means for converting a pneumatic signal corresponding to the weight applied to said scale into an electrical weight signal;
• means for zeroing the weight signal so that the weight signal equals zero volts when the predetermined weight is applied to said scale;
• latch means for storing and providng a tare signal corresponding to the weight of any residue on said scale after said flowable material has been emptied from said scale;
• first summing means for summing the weight signal and the tare signal to produce a net weight signal;
• an analog to digital converter coupled to said first summing means for converting said net weight signal into a digital net weight signal;
• manual means for producing a setpoint signal to control the weight at which the termination of material flow will be triggered;
• a programmable controller means coupled to said analog to digital converter, said programmable controller means including:
• means for periodically resetting the tare signal stored in said latch means,
• means for calculating an average weight and a standard deviation for the net weights of the final amount of flowable material measured on said scale after said material stops falling onto said scale, and
• means for producing a computer setpoint signal as a function of the average weight, the standard deviation and the predetermined weight;
• second summing for receiving and summing the weight signal, the tare signal, the setpoint signal and the computer setpoint signal to produce an adjusted signal;
• and
• comparator means for comparing said adjusted signal to zero volts and for producing a triggering signal to terminate the flow of material upon said adjusted signal becoming equal to zero volts.

An electronic pneumatic scale for repeatedly weighing flowable material in a scale bucket comprising:

• spring means for suspending said scale bucket;
• an air circuit having an opening aligned with said spring means such that the air pressure in said air current is responsive to the position of said spring means and thereby the weight on said bucket;
• air pressure to voltage transducer means connected to said air circuit for producing a weight signal corresponding to the weight applied to said scale bucket;
• means, responsive to the weight signal, for triggering the termination of said flow of material.