| 摘要 |
<p>Weighing apparatus including variable capacitance load sensing means 20, a capacitance detection circuit 22, an analog to digital convertor 25 and microcomputer control means 28 is automatically verified for accurate operation. The capacitance detection circuit 22 is provided with a computer controlled verification switch 94 by which the value of a parameter, such as resistance in an attenuation circuit, can be changed. Automatic verification of correct operation is obtained by periodically, with no weight on the scale, obtaining a first weight reading, operating the verification switch 94 to change the parameter and obtaining a second weight reading. The difference between the two readings is a verification value and is compared to a stored verification value obtained in the same manner during calibration and stored for later use. If the difference between the obtained and stored verification values exceeds an allowable limit, the scale may be disabled from further weighing.</p> |
