| 摘要 |
PURPOSE:To avoid the fluctuation of offset by time and to supply the signal component only at all times to an A/D converter, by storing an offset component to a storage means in the form of a digital signal. CONSTITUTION:An analog input signal from a measuring electrode 1 is amplified at a differential amplifier 32, inputted to an A/D converter 33 and converted into a digital signal. This converted digital signal is stored in a memory via a buffer 34 and a data bus and given to a data latch 36 for storage. On the other hand, when the analog input signal is zero, the offset being the output of the amplifier 32 is in A/D conversion and stored to the data latch 36, and the stored offset is read out and converted into an analog signal by a D/A converter 35 and given to one input of the differential amplifier 32 to output the signal component only. |
