The principle of the bar code scale is also relatively simple. The portable bar code machine is built on the basis of the electronic scale. The printing information format of the product is set in advance, and the bar code paper can be clearly printed out when used.

When an object is placed on the weighing pan, pressure is applied to the sensor, which deforms, causing the impedance to change, while using a change in the excitation voltage to output a varying analog signal. The signal is amplified by an amplifying circuit and output to an analog to digital converter. The digital signal converted into a convenient processing is output to the CPU arithmetic control. The CPU outputs the result to the display according to the keyboard command and the program, and also outputs it to the portable printer, and prints the barcode label.

Bar code scales are mainly used in supermarkets to weigh and print barcodes.