| 摘要 |
PURPOSE:To improve the metering accuracy by theoretically elliminating the error due to the offset of an A/D converter in response to the positive and negative digital signals which are generated by changing the polarity of the input of the A/D converter. CONSTITUTION:The analog signals A of a transducer 1 are fed through a notmally closed contact 6b to an A/D converter 3, where they are converted into digital signals Dp so that they are fed to a date processing device 51. This device 51 partly stores the digital signals and partly operates an auxiliary relay 6 thereby to open a normally closed contact 6b but to close a normally open contact 6a. As a result, the A/D converter 3 converts the analog signals having inverted polarity into digital values DN and feeds them to the data processing device 51 so that they may be stored. The device 51 calculates the digital values of (DP - DN)/2 and displays or stores it while stopping its output which has been fed to a signal line 7. By periodically repeating a series of such operations, the error due to offset can be eliminated. |
