| 摘要 |
PURPOSE:To set a measurement information voltage like a tap value information voltage which has such minimum value that it is not affected by noise by providing variable resistances to set a scale conversion coefficient and a bias voltage. CONSTITUTION:An operational amplifier 1 which applies the measurement information voltage to an input terminal, a first variable resistance 2 which is connected between the output terminal and the input terminal of this amplifier 1 to set the scale conversion coefficient, and a second variable resistance 4 which sets the bias voltage to be added to or subtracted from the measurement information voltage to the input terminal of the amplifier 1 through a high resistance 3 are provided. When the measurement information voltage like the tap value information voltage of a transformer in the range where the minimum value is higher than 0V and the maximum value is a prescribed value, for example, 5V is converted to a BCD (binary coded decimal) code and is transmitted, the scale conversion coefficient is set by the variable resistance 2 for feedback of the operational amplifier 1 and the bias voltage is set by the variable resistance 4 and is added to or subtracted from the measurement information voltage. Thus, the minimum value of the measurement information voltage is easily raised to such value that it is not affected by noise. |
