Apogee Instruments TS-210 Manuel du propriétaire - Page 15

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Fan Operation

Under some environmental conditions (e.g., high wind speed, low solar radiation), accurate measurements can be

made without running the fan at full speed. Fan speed and power consumption can be decreased using a pulse

width modulation (PWM) signal. The PWM signal should have a frequency of approximately 20 kHz and a duty

cycle of 50 to 100 %, where a duty cycle of 100 % is full power and 50 % is low power. Running the fan in a low

power mode reduces the current draw from 80 mA to approximately 25 mA. The only way to completely stop the

fan is to turn the power off. Apogee Instruments also offers 12 V DC fan options for purchase (see TS-100 series).

The fan also has a tachometer to monitor blade revolutions per minute (RPM). The tachometer outputs a pulse

voltage signal. The pulse multiplied by 30 yields fan RPMs. The RPM should be near 4500 in full power mode and

2500 in low power mode. In addition to the tachometer output wire, there is a pull-up wire (power input). This

allows a user-defined maximum output voltage from the tachometer and facilitates interfacing with multiple

measurement devices.

White: Pulse Counter or Control Port (tachometer output)

Black: Ground (power)

Green: Control port (controls fan speed using pulse width

modulation)

Blue: Voltage Source (power input for tachometer; must

be less than 30 V)

Red: 24 V DC (positive fan lead)

Clear: Shield Ground