A Measurement System With Wide-Range High-Input Resistance and Float Input

There are two problems to be met often in the measure practice of AC and DC voltage, one is that the input resistance of the measurement circuit would divide the input source voltage measured. Another is the short circuit destruction and common-ground disturbance caused by the common-ground between the measurement circuit and the source voltage measured. Aiming at the two problems above, the authors had designed a floating ground measurement system with high-input resistance, which divide the plusmn1000 V into four ranges and convert every range within the range of plusmn5 V in order to meet the need of most of the A/D converters for input voltage range. The input resistance is greater than 10 GOmega when the input voltage is less than 50 V and 1MOmega the input voltage above 50 V. There are wide applications in measurement and instruments, specially, in the design of signal acquisition units controlled by computer.