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Grid dip oscillators were first developed in the 1920s and were built with vacuum tubes.The devices displayed the amplitude of the tube's grid current, hence GDO.. Modern dip meters are solid-state devices, and are sometimes called gate dip oscillators or emitter dip oscillators in reference to the analogous part of the transistor whose current is measured instead of a vacuum tube grid. [1]
Using a PMU, it is simple to detect abnormal waveform shapes. A waveform shape described mathematically is called a phasor.. A phasor measurement unit (PMU) is a device used to estimate the magnitude and phase angle of an electrical phasor quantity (such as voltage or current) in the electricity grid using a common time source for synchronization.
A tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. [1] The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common.
On every range, at full-scale voltage of the range, the full current required to deflect the meter movement is taken from the circuit under test. Lower sensitivity meter movements are acceptable for testing in circuits where source impedances are low compared to the meter impedance, for example, power circuits; these meters are more rugged ...
Microwave-frequency absorption frequency (or wave) meter. A frequency meter is an instrument that displays the frequency of a periodic electrical signal.Various types of mechanical frequency meters were used in the past, but since the 1970s these have almost universally been replaced by digital frequency counters.
The term smart meter often refers to an electricity meter, but it also may mean a device measuring natural gas, water or district heating consumption. [1] [2] More generally, a smart meter is an electronic device that records information such as consumption of electric energy, voltage levels, current, and power factor.
Friden made a calculator that also provided square roots, basically by doing division, but with added mechanism that automatically incremented the number in the keyboard in a systematic fashion. The last of the mechanical calculators were likely to have short-cut multiplication, and some ten-key, serial-entry types had decimal-point keys.
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and output frequencies the same, thus a phase-locked loop can also track an input frequency.