Measurement of the phase angle and speed of the machine set
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For the phase measurement of the engine set, the 3500 system is used; the signal is three-wired – for power supply, COM, and the signal itself. The system requires power supply, and a preamplifier is installed in the circuit. In contrast, the speed probe has only two wires, and no preamplifier is present in its circuit. May I ask what are the principles behind the probes used to measure key phase and those used to measure rotational speed, and what are the model numbers of these probes?
The key phase probe uses the same eddy current sensor as the displacement probe. I’m not sure what kind of speed probe you’re using; it might be a proximity switch.
Speed sensors are mostly electromagnetic sensors. Its structure is simply a coil; when a magnet (which can be the residual magnetism of metal) passes by the front end, an electrical pulse is generated within the coil based on the principle of generators. When the number of passes of the magnet is related to the rotation speed, the pulse frequency is related to the rotation speed. Since it is only about the generation and transmission of pulses, signal processing (pre-amplifier) is not required. A phase-sensitive sensor is an eddy current sensor; macroscopically, its structure is no different from that of an electromagnetic sensor (it consists of just a coil), but the specific parameter requirements differ significantly. ● A phase-sensitive sensor is essentially also an inductive coil; when the core of the coil (the metal object being measured) and the position of the coil change, the inductance also changes ； ● When an inductor is part of an oscillating circuit, changes in its inductance lead to changes in the oscillation frequency; this frequency reflects the positional relationship between the coil and the metal object being measured ； ● To avoid the influence of the distributed parameters of the coil’s connection wires to the oscillation circuit (the inductance and capacitance of the wires), the coil cannot be placed too far away from the entire oscillation circuit; therefore, a preamplifier is used to ensure that the components of the oscillation circuit are not too distant from each other. (Naturally, power supply is required.) (This statement differs from the one in the figure below in terms of perspective and focus, but the principle remains the same.) ) If a phase sensor emits (uses) only one signal per rotation, it can also be called a speed sensor.
Additional note: The speed signal for Line 2 is a frequency signal that is measured directly; the card slot channel is powered, so no additional 24V power is required.