1. Introducere în măsurarea vitezei de preîncălzire a aerului
The air preheater is an important large-scale operating equipment in the power plant. The failure of the rotary air preheater directly leads to reduced load operation or shutdown, and the rotary air preheater takes a long time and is difficult to maintain. Therefore, precise measurement of the rotation speed of the rotating air preheater, real-time alarm and protection of abnormal rotation speed are of great significance for the safe and stable operation of the entire unit and reducing unplanned shutdowns.
The air preheater has a slow speed, about one revolution per minute ({{0}}.999 revolutions/min). It requires high-precision measurement of the speed of one revolution per minute, and general measurement methods cannot be used. If the measurement system is required to convert once per second, output with a standard signal of 4-20, and the accuracy of the D/A converter is 12 bits (accuracy of 0.25‰), then at normal speed, at least 4096 pulses must be received per second , That is, at least 245760 pulses are received in one revolution. In this case, only the more advanced grating sensors can be used to achieve such measurement accuracy.
2. Senzor grilaj
Grating technology has appeared for more than 100 years. With the development of grating engraving technology and electronic technology, grating sensors have developed rapidly in the past two to three decades. It has been widely used in precision measurement of speed and length.
Avantajele senzorilor cu grilaj:
a. The output natural digital signal. The so-called natural digital quantity means that its original output signal is a pulse signal, so it is easy to adapt to a digital circuit.
b. High precision. Under the guarantee of the advancement of photolithography and electronic subdivision technology, and the moiré fringe has the effect of eliminating local errors, the accuracy of grating sensing measurement can be made very high. (The whole circle is 162000 grid lines)
c. Strong anti-interference ability. Because it is a digital output, the signal amplitude is high, so it has strong anti-interference ability against weak signals.
d. Small inertia. Compared with other types of sensors, since the grating sensor is a thin disk, the mass and inertia are small. In this way, when composing the system, it has little impact on the dynamic performance of the system.
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