SmartFan^® TachScan-9

Operation

SmartFan TachScan-9 Fan Monitor Speed Alarm

Setting Alarm Trigger Speed(J10)
Use jumper at J10 to set the alarm trigger speed (W_A):

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%.

NON-ISOLATED ALARM OUTPUTS (J13)

The 60VDC Tachscan-9 (030M920-F) offers nine separate non-isolated alarm outputs plus an OR’d fan failure signal at header J13. Pins labeled 1 through 9 correspond to fan headers labeled J1 through J9.

The 75VDC Tachscan-9 (042M920-F) triggers a single alarm output if any of up to nine fans falls below the set trigger speed.

All versions of the Tachscan-9 can drive:

Connecting LED’s to J13
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. Refer to the wiring diagram in Figure 1 (located on the Installation page).

For the 60VDC Tachscan 9 (030M920-F), each of the pins labeled 1 through 9 on J13 will supply 8 mA to an LED connected between that pin and pin J13:- or J13:+. To turn on an LED in response to a fan failure (usually a red LED) connect it between the appropriate pin and pin J13:-. The cathode (negative lead) of the LED is connected to pin J13:-. To turn on an LED indicating that there has not been a failure (usually a green LED) connect it between the appropriate pin and pin J13:+. The anode (positive lead) of the LED is connected to pin J13:+.

For the 75VDC Tachscan 9 (042M920-F), a red LED will turn on in case of any fan failure when the anode is connected to “R” and the cathode is connected to “-“. A green LED will turn off in case of any fan failure when the anode is connected to “G” and the cathode is connected to “-“. A bicolored, 2 pin LED can be connected across “R” and “G”. A bicolored 3 pin LED can be connected at “R”, “G” and either “-“ pin (cathode).

Connecting Logic Circuits to J13
Reference table 2 for 042M920-F or table 3 for 030M920-F. A logic circuit connected to J13 must have a ground reference connected to the Tachscan-9 circuit ground available at J13: -, J11:-, and J1 through J9:-. If the logic ground and Tachscan-9 circuit ground are common, only the appropriate pin on J13 need be connected to the logic circuit. If not, connect pin J13:- to the ground or negative terminal of the logic circuit.

When in a LOW state, the connected pin can sink at least 1.0 mA at = 0.4VDC. When in a HIGH state, the connected pin will source = 2VDC. In case of a power failure to the TachScan board, all J13 outputs are open. Connection of an external “pull-up resistor” will ensure an alarm state in case of power failure.

Connecting Optical Isolators or MOS Relays to J13
A resistor must be connected in series with the input to the optical isolator or MOS relay but otherwise it is connected in the same manner as an LED (see Connecting LED’s to J13). A 1/4 watt resistor with a value of approximately 200 Ω is recommended to set isolator input current to approximately 5 mA.

Isolated OR’d Alarm Outputs (J12)
These optically isolated outputs provide both normally open (N.O.) and normally closed (N.C.) alarms permitting connection to logic circuits or other loads with no electrical connection to the TachScan-9 circuit.

The outputs are 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, and a maximum of 230 VAC can be applied to the alarm terminals. The outputs also trigger in the event of cooling system power failure.