摘要:
In a measuring differential amplifier having first and second input terminals for subtracting a first signal applied to the first input terminal from a second signal applied to the second input terminal to obtain a subtraction and for outputting a signal corresponding to A times of the subtraction, a circuit for reducing an offset generated during measurement. Prior to the measurement, the second signal is applied to the first and second input terminals so that the differential amplifier outputs a voltage corresponding to A times of a difference between the second signals, i.e., A times an offset voltage. At this time, the differential amplifier is connected at its output terminal to one end of a capacitor grounded at the other end so that the voltage corresponding to A times of the offset voltage is applied to the capacitor for charging. During the measurement, the output terminal of the differential amplifier is disconnected from one end of the capacitor so that the voltage charged in the capacitor is applied to the adder and multiplied by 1/A to become again the offset voltage. The adder adds a signal indicative of the offset voltage to the first signal to obtain an addition signal and supplies the addition signal to the first input terminal of the differential amplifier. Thus, the input offset voltage is canceled by an offset voltage newly generated at the differential amplifier.
摘要:
The present invention discloses a system and a method for transmitting data in a shield machine and for calculating the filling amount of a void by detecting the distance to the natural ground. The system and the method are capable of transmitting analogue signals or signals of relatively high frequencies with reliability, enabling an unskilled operator to accurately detect buried articles and accurately carry out the back-filling work. Therefore, an optical rotary joint (100) is disposed between a rotary cutter head (10) and a non-rotary shield body (2) to count time taken to detect the peak value of a reflected signal larger than a standard value or time taken to detect the zero cross position present prior to the peak value. In accordance with the counted time, the distance between the antenna and the natural ground is calculated and displayed. Then, the void volume is calculated in accordance with the distance so that a target value of the back-filling amount is set.
摘要:
A method and an apparatus for performing measurement by a resistivity method in order to detect the thickness of a sludge layer on the outer periphery of a shield machine. A Wenner electrode row (14) on the outer periphery of the machine is used to measure reference resistivities to thereby detect certain resistivities in the depth direction of the natural ground and the sludge layer thickness. At the same time, a dipole electrode row (16) is used to measure voltage distributions in the depth direction of the natural ground and in the direction of the arrangement of the electrodes. The ratios of the values measured by the measurement dipole electrodes to those measured by the reference Wenner electrodes are calculated, and their distribution is charted. When mutually equal values in the distribution map are connected together by continuous curves, a contour-pattern image is obtained, which enables a configuration of the collapse of natural ground to be determined. Such as image can be displayed either two-dimensionally or three-dimensionally by image processing. If a plurality of sets of electrode rows (14) and (16) are arranged in the circumferential direction of the machine, and resistivities are detected while current having different frequencies is supplied, the collapse of the natural ground can be measured quickly.
摘要:
A position measuring apparatus easily and accurately detects the position of an underground excavator, such as a shield excavator, during the underground excavation, and particularly the position thereof on a horizontal plane. The position measuring apparatus comprises a transmitter (10) including at least two cable loops (10a, 10b) which generate AC magnetic fields; a receiver (30) which detects the AC magnetic fields and produces signals representative of the detected fields; and a computing unit (60) which identifies the signals with respect to the originating cable loop and which calculates the position of the underground excavator (20). The two cable loops (10a, 10b) are substantially perpendicular to each other. The receiver (30) includes two magnetic field detecting elements (S.sub.1, S.sub.2) which are substantially perpendicular to each other. The receiver (30) is rotatably driven so as to maintain the magnetic field detecting elements (S.sub.1, S.sub.2) at constant angles to the cable loops (10a, 10b).