220V Cooling Fan monitoring methods

So far there are alarm sensors and the speed sensor are two types of "220V Cooling Fan" self-monitoring methods, the use of the alarm sensor in the fan speed is lower than an alarm signal when a certain threshold, and fan speed signal output can be realized Real-time monitoring of speeds. "220V Cooling Fan" is necessary driving DC power supply! Voltage DC power supply used must be marked on the fan operating voltage of the same. Battery is a DC power supply, if using it to drive "220V Cooling Fan", in addition to the charge depends on the battery voltage outside the operating voltage of the fan are the same. If not necessary to use DC / DC converter of the voltage becomes the same.