Speed ​​calculation method for proximity switches and high-speed counters - News - Global IC Trade Starts Here.

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Photocoupler

(1) M method: It is to count the number of output pulses of the photoelectric code disc in a certain time interval, and calculate the rotation speed, which is suitable for high-speed measurement of the generator speed.
(2) T method: It is a measurement method for calculating the motor speed by measuring the pulse period of the photoelectric code disk.
(3) M/T method: It combines the advantages of M method and T method, and has high resolution and measurement accuracy in low speed and high speed sections.
(4) E/T method: The principle is to start from the T method, just to overcome the accuracy problem of the T method at high speed.
Combining FX2N plc with the speed measurement range of the hydropower generating unit (0~600r/min) and the simpleness of M method for measuring the hardware speed, this paper uses the M method for speed measurement and calculation.
Assuming that the photoelectric code disk coaxially connected to the generator rotates once a week, the number of output pulses is P, the rotational speed of the motor is n (r/min), the detection time is T(s), and the number of counting pulses in T is m. Then the motor speed n is:
n = 60m/pt
In the detection time T, the error is at most 1 pulse, then the M method speed resolution Q is:
Q = 60 (m + 1) / pt - 60m / pt = 60 / pt
It can be seen that when using the M method to measure the speed, the resolution is independent of the magnitude of the speed. In order to improve the resolution, except for the optoelectronic code disc with a large number of output pulses per revolution, only the detection time is increased as much as possible, but the detection time is too large. The more severe the feedback delay of the speed, the serious impact on the dynamic and static performance of the system.