Currently on the market, there are two types of monitoring methods for DC cooling fans: alarm sensor and speed sensor. The alarm sensor can give an alarm signal when the fan speed is lower than a certain threshold, and the speed signal output can realize the fan speed. Real-time monitoring. Obviously, the higher the air volume, the higher the heat dissipation capacity of the DC cooling fan. This is because the heat capacity ratio of the air is constant, and the greater the air volume, that is, the more air per unit time can take away more heat. Of course, the heat dissipation effect is related to the way the wind flows under the same air volume.
The speed signal output from the fan circuit is usually in the form of pulses, and each wave head indicates that the fan has rotated one revolution. Such signals can be directly provided to the host for display through the data bus. The speed signal output by some fans is not the real speed of the fan, but a multiple of the speed. For example, every revolution generates 2, 4, or 6 pulses, which must be processed to form a real speed signal reflecting the fan. If you want to distinguish whether the fan speed is the real speed or a certain multiple, you can use the tachometer to measure the actual speed, and then compare it with the displayed data.
The alarm signal output from the fan circuit has two states: "high level" and "low level". The meaning of the two levels is generally in accordance with the positive logic system. High level means "fault" and "low level". Means "normal".
The speed signal output from the fan circuit is usually in the form of pulses. Each wave head means that the fan has rotated one circle. Such signals can be directly provided to the host through the data bus for display. The speed signal output by some fans is not the real speed of the fan, but a multiple of the speed. For example, every revolution generates 2, 4, or 6 pulses, which must be processed to form a real speed signal reflecting the fan. If you want to distinguish whether the fan speed is the real speed or a certain multiple, you can use the tachometer to measure the actual speed, and then compare it with the displayed data.
The speed measurement signal of the fan is generally output from a three-lead plug. The yellow and black of the three leads are +12V power and ground respectively, and the other color line is the speed signal output line. It should be noted that the third lead of some three-lead fans is not a speed measurement signal output line, but a speed control signal line, through which the speed control signal is input to the fan motor.
