Testing – Fan Speed Control and Monitoring
To test the fan speed monitoring and control functions of the ZM-MFC2, I measured the actual fan speed with an optical tachometer and measured the DC output voltage to the 3-pin fan with a volt meter. A standard 3-pin fan was used on channel #1 and a PWM 4-pin fan was used on channel #4.
- Panaflo 92mm (FBA09A12H1BX) 3-pin (2,850 rpm)
- Intel OEM P4 OEM HSF with PWM, 4-pin
- Extech Photo Tachometer 461895
- FLUKE 87-III True RMS digital multimeter
The fan speed was measured with a photo tach by placing a small reflective dot on one of the fan blades and then compared to the displayed fan speed. Voltage measurements were also recorded for the 3-pin fan.
FAN 1: 3-pin, voltage speed control
Note: The Panaflo 92mm H1BX stopped turning when the set point speed was turned down to 600 rpm. The Panaflo would continue running at below 5 VDC but would not always start. With set points that generated at least 5 VDC output, the Panaflo fan would start and run reliably.
FAN 4: 4-pin, PWM speed control
The PWM 4-pin fan never stopped turning, even when the set point was turned down below the fan’s minimum speed; it just stayed at the fan’s minimum working speed.
Note 1: In either case, a connected fan can not be made to run faster than its maximum rated speed. Setting the rpm to 4,000 rpm while using a 2,400 rpm fan will have no effect; the fan will still run at 2,400 rpm.
Overall, fan speed control proved to be very good and the displayed rpm values were quite accurate.