Zalman ZM-MFC2: 4 x Fan Controller + Power Meter

TESTING

Ambient conditions during testing were 23°C and 115 VAC.

Power Meter

The power meter reports the total amount of power consumed by everything connected to the power supply, including the controller itself. The meter itself is a little black brick that is inserted between the AC plug and the power supply. It is similar to the Kill-a-Watt power meter that we use to measure power in the lab, but it doesn't report anything except wattage. It is accurate enough for everyday purposes, reading about 2% higher than the meter we usually use.

Beside the numerical display is a visual bar meter that supposedly tracks the numerical amount, but the resolution is too coarse to be of much use: It has only four different stages, with the length of the bar changing every 200W. Since our test system never exceeded 200W, this meant that the bar meter never changed, no matter how heavily loaded the system was. Even very power-hungry systems are unlikely to push the meter beyond the second bar. Doing so would require a system that draws in excess of 400W!

Fan Control

Aside from the interface quirks mentioned earlier, fan control was simple and straightforward. Rotation speed is set directly, without taking thermal data into account. Some tinkerers may miss the ability to set fan speed according to temperature, but leaving the fans running at a constant speed makes good sense from a silencing perspective, as it prevents sudden noise spikes that draw attention to themselves.

Users with fans that buzz when controlled by PWM will be happy to know that the ZM-MFC2 uses direct voltage control to modify fan speed — with the obvious exception of the fourth 4-pin fan channel. Zalman reports the output range as 4V~11V, but the actual range appeared to be highly dependent on what fan was connected, and we observed everything from 3.23~12.29V during our tests. As a general rule, lower current (slower, smaller) fans were supplied with lower voltages than high current fans.

Zalman advertises the adjustment range as 60~5940 RPM, and they're not kidding about the low end of the scale. We had no problem stalling any of the fans we tested, so some caution is advisable when cranking down the fan speed. This is a strong point in favor of the ZM-MFC2, as most controllers do not permit reducing the speed to the point of stalling. However, it is also somewhat dangerous, as it is quite easy to reduce fan speed to the point overheating. Unlike many products on the market, the ZM-MFC2 has not been idiot-proofed!

A small degree of safety is provided by the auto-restart function that boosts the voltage if the controller detects a stall. By default, a stalled fan will cause an audible but surprisingly inoffensive beep to go off and the voltage will be spike briefly to 12V to restart the fan. If the fan setting is too low, this will cause the fan to cycle in bursts. The alarm can be disabled if it is too irritating (or there is no fan connected), but this is probably not advisable during ordinary operation. If something goes wrong, it's good to know about it!

Fan speeds are regulated based on the rotation speed reported by the fan, so 2-pin fans and other fans that do not provide a tachometer lead cannot be controlled. Some nonstandard fans that do not output two clock pulses per rotation may also work incorrectly.

Unfortunately, given that most fan tachometers are unreliable below ~500 RPM, fan control below this level seemed to be equally unreliable. Below this level, the display reported 0 RPM but fan control continued to work down to the fan's stall point. However, the controller clearly had difficulty figuring out what voltage to output in this situation, as the fan speed tended to wander slightly at very low speeds. This caused a warbling effect that was more or less audible depending on the fan.

Thermal Monitoring

Thermal monitoring worked as expected. All of the sensors read identically at room temperature (23°C) and accurately matched the other thermometers in the test lab. The sensors also correctly read the reviewer's skin temperature as 34°C.

FINAL CONCLUSIONS

The ZM-MFC2 has two very strong points in its favor: A wide control range that allows adjustment to below the stall voltage of most fans, and the ability to measure power consumption. That said, they are balanced by two design flaws: A clumsy interface, and a narrow viewing angle.

Both of the strong points are unusual enough to push Zalman ahead of the competition, but we couldn't help thinking that they could be improved even more. To this end, we came up with a wish list of things we would like to see:

• A fix for the wandering fan speed by fixing the output voltage permanently once the target speed has been found.
• A higher resolution bar graph to go with the power meter — perhaps with a variable scale based on the highest power draw ever observed.
• A log function for the power meter that tracks power usage over time.
• The optional ability to set fan targets based on thermal (or power) data, or to set a second target once a certain threshold is reached.

As it stands, the ZM-MFC2 is a useful product that will appeal to users who can't find its unique features anywhere else. The power meter is certainly a feature we applaud; every eco-savvy computer user should have one! Its usability issues hold it back from must-have status. Hopefully, Zalman will stand behind its product and release an updated version with the bugs worked out.

Much thanks to Zalman for the ZM-MFC2 sample.

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