SmartFan^® TachScan-3

Operation

SmartFan TachScan-3 Fan Speed Alarm

Settings (J4)
Alarm Channel Setting: Use this jumper to specify the number of fan tachometer signals that will be monitored, from 1 to 3. Each jumper setting label corresponds to the number of fans to be monitored. For example, if only two fan tachometer signals are going to be monitored set the jumper to the “2” position. The factory setting is “3.”

Settings (J5)
Trigger Speed (W_A): Use this jumper to set the trigger speed

Position L = 1000 PPM
Position M = 2000 PPM (Factory Setting)
Position H = 4000 PPM

Since fan tachometer circuits are designed with one, two, or even more pulse outputs per revolution, settings are listed in pulses per minute (PPM) rather than revolutions per minute (RPM). Given the fan’s rated speed (W) and number of pulses per revolution (N), use the following formula to select the trigger speed (W_A):

W_A = W x N x 0.4

(Note: When used with a SmartFan speed controller the factor in the above equation should be changed from 0.4 to 0.3.)

For example, a 3300-RPM fan with two pulses per revolution would have a trigger speed (W_A) of

W_A = 3300 RPM x 2PPR x 0.4 = 2640 PPM

Since the 2000 PPM trigger is closest, set jumper J5 to the “M” position.
The alarm trigger accuracy is +/- 20%.

LED Outputs – (J6)

Both normally on (green) and normally off (red) LED outputs are provided. Two leaded and three leaded (common Cathode) Bi-colored LEDs can also be used. Choose LEDs with rated forward voltage (V_f) between 1.6 and 2.4 VDC at forward current (I_f) of between 15 and 25 mA. Nominal current applied to the LEDs is 8 mA.

Isolated Alarm Outputs (J8)
These outputs provide both normally open and normally closed isolated outputs permitting connection to logic circuits or other loads with no electrical connection to the TachScan-3 circuit.

Part Numbers 030M320-F and 030M3205-F provide simultaneous open collector outputs from optical isolators, which are intended to drive logic circuits. These outputs can sink up to 1.0 mA at 0.4 VDC. A maximum of 30 VDC can be applied to alarm terminals. The normally closed output also triggers in the event of cooling system power failure.

Part Numbers 030M320R-F and 030M320R4-F provide simultaneous outputs from a Dual-Pole MOS Relay, which are intended to drive heavy loads. These outputs have a maximum on-state resistance of 50 O. Maximum sinking current is 100 mA. A maximum of 230 VAC can be applied to alarm terminals. The normally open output also triggers in the event of cooling system power failure.