Patent GB-1491323-A (GB)
Title: Weight measuring apparatus
IPC: G01G19/415
Filed: 1975-01-20
Abstract: 1491323 Weighing apparatus RELIANCE ELECTRIC CO 20 Jan 1975 [18 Jan 1974] 2389/75 Heading G1W A weighing apparatus having a digital weight output of a predetermined number of digits comprises scale means for generating a digital weight signal having a less significant digit than the weight output, a memory for storing a zero correction factor, means for periodically generating a corrected weight from the algebraic sum of the generated weight signal and the zero correction factor stored in the memory, the most significant predetermined numbers of digits of the corrected weight providing the weight output, and means responsive to the corrected weight falling within a predetermined small weight range (which denotes zero load on the scale means) for periodically modifying the zero correction factor stored in the memory by a predetermined amount less than the least significant weight output digit to decrease the absolute value of the corrected weight towards zero. The predetermined small weight range may be 0 to 0À005 lbs and the predetermined amount 0.001 1bs. A zero light indicates when the zero is within “ of the least significant digit displayed. A digital signal representing the weight on platform 13 is passed to a microcomputer 15 which is also connected to a data input unit 17, a digital weight display 22 and a printing unit 21. The microcomputer calculates the net weight of an article and its value and causes these quantities and the price per unit weight to be printed out on a label at 21. Unit 17 Fig. 3 comprises switch busses 155 connected to the computer, and a series of switches for connecting various strobe signal lines from the computer to selected ones of the busses. The tare weight of a container may be entered manually by means of switches 165, 166. When one of the manual tare switches is pressed the computer sums up the values of the switches pressed in a three second period and places this value into the tare memory. "Auto tare" and "no tare" switches 170, 171 respectively allow the computer to automatically tare or apply zero tare to the weighing. The price per pound may be applied to the computer either by manual switches 159-161 in unit 17. Alternatively, when switch 174 in unit 17 is pressed, the price is supplied automatically from the printer unit 21 which reads a digital code on a commodity plate inserted in the printer, the plate also carrying raised type for printing the article name. The printer may be controlled by switch 172 in unit 17 to print a label for each weighing, to print a new label each time a label is removed, or to print labels continuously. Unit 17 contains a switch 177 which inhibits the auto zero action, and a captive range expand switch which allows zero errors up to 0À6 lb to be accumulated in a register. A zero expand switch 178 moves the decimal point one place to the left to increase the sensitivity by a factor of ten. The computer is arranged to prevent the printing of a label if a previously printed label has not been removed from the printer, if a previously weighed object has not been replaced, or if the maximum weight capacity or maximum value capacity has been exceeded. If the price per lb or tare value has been changed from a previous weighing, a lock switch 179 in unit 17 must be actuated before a label is printed. The printer includes printing wheels provided with commutators producing digital signals representing the position of the wheels, and printing of a label is inhibited if these signals are incorrect. A service switch allows the price per lb or value stored in the computer to be displayed on display 22 to determine whether or not an error in a printed label is caused by the printer. Blanking switches are provided whereby any of the net weight, price per lb and value print outs may be inhibited manually. The computer and printer may also be used to print labels according to number rather than weight by operation of switch 172 in unit 17.