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A theodolite is used to measure the horizontal angle between indicators on the two ends of the subtense bar. The distance from the telescope to the subtense bar is the height of an isosceles triangle formed with the theodolite at the upper vertex and the subtense bar length at its base, determined by trigonometry.
More advanced current probes combine a Hall effect sensor with a current transformer. The Hall effect sensor measures the DC and low frequency components of the signal and the current transformer measures the high frequency components. These signals are combined in the amplifier circuit to yield a wide band signal extending from DC to over 50 MHz.
A theodolite (/ θ i ˈ ɒ d ə ˌ l aɪ t /) [1] is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying , but it is also used extensively for building and infrastructure construction , and some specialized applications such ...
The sensor circuit is supplied with constant current. A distinguishing feature of the IEPE principle is that the power supply and the sensor signal are transmitted via one shielded wire. Most IEPE sensors work at a constant current between 2 and 20 mA. A common value is 4 mA. The higher the constant current the longer the possible cable length.
The surge is defined by the Combination Wave Generator's open-circuit voltage and short-circuit current waveforms, characterized by front time, duration, and peak values. With an open circuit output, the surge voltage is a double exponential pulse in the form of k ( e − α t − e − β t ) {\displaystyle k(e^{-\alpha t}-e^{-\beta t})} .
It is only after this round-trip delay that the short can be detected by the TDR. With knowledge of the signal propagation speed in the particular cable-under-test, the distance to the short can be measured. A similar effect occurs if the far end of the cable is an open circuit (terminated into an infinite impedance).
The chevron test is used to determine the fracture toughness of brittle construction materials. The fracture toughness is a basic material parameter for analyzing the bond strength. The chevron test uses a special notch geometry for the specimen that is loaded with an increasing tensile force.
Variations in the electrical conductivity and magnetic permeability of the test object, and the presence of defects causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the coil, which is a telltale sign of the presence of defects. [5]