| 摘要 |
The present electronic weighing apparatus comprises a load convertor, a direct current amplifier for amplifying the converted output, an analog-digital converter controlled by an enable signal for the analog-digital converting of the output from the dc amplifier, an enable signal generator for providing a periodical conversion enable signal to the analog-digital converter, and a digital display for displaying the output from the analog-digital converter. A zero tracking circuit is connected between the A/D converter and the display and comprises a storing circuit responsive to a store enable signal for storing the output from the analog-digital converter, a digital subtracter for evaluating the difference between the output from the analog-digital converter and the output from the storing circuit. The output from the digital subtracter is applied to the digital display as the weighed output. A zero judging or sensing circuit determines whether the output from the digital subtracter is zero. A threshold level detector detects when the output from the digital subtracter exceeds a predetermined threshold value, and a retriggerable monostable multivibrator normally assumes the "one" storing state and is responsive to the simultaneous occurrence of the zero sensed output or the threshold detected output and the conversion enable signal and is triggered to assume the other state for a predetermined time period. Said "one" state of the monostable multivibrator at any time other than said predetermined time period is applied to the storing circuit as a store enable signal, thereby to renew the data in the storing circuit. |
