| 摘要 |
PURPOSE:To attain an offset correction in a short time and with highs accuracy without applying load on to a CPU by performing the offset correction after subtracting the offset value obtained when an input point is short-circuited from the input signal value. CONSTITUTION:A CPU controls a controller 5, turns on a switch Q3 with a signal T1 and connects an input part 2-1 to an analog processing part 4. At the same time, the controller 5 outputs a signal T10 to a driver 23 at the primary side and turns off a switch Q4 with a signal T11 together with a signal T12 and a switch Q5 turned on respectively. Then the input side of an amplifier 10 is short-circuited. The output value (e) of the amplifier 10 is turned into the offset value eoff at a time point when the switch Q5 is turned on. The value eoff is modulated by the ON/OFF of both switches Q1 and Q2 and outputted to sample holding circuits 16, 17, 20 and 21 via a buffer amplifier 15 to be held there.
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