A claimed 35,000 RPM speed rating for a 12V 4028 fan places it firmly in the realm of ultra-high-performance, specialized industrial equipment. This is not a fan for a personal computer; it is a component you would find in mission-critical servers, high-end networking hardware like routers and switches, or certain medical devices. Testing such a fan is a serious undertaking that requires specialized equipment and strict safety precautions due to the immense forces involved.

The Reality of 35,000 RPM:

At 35,000 RPM, the tip of the fan blade is moving at a significant fraction of the speed of sound. The centrifugal forces on the blade structure are enormous, requiring materials and manufacturing techniques of the highest grade to prevent catastrophic failure (the blade disintegrating). These fans often use reinforced polyamide or other composite materials for the blades and a specialized, incredibly powerful multi-phase brushless DC motor that far exceeds the capabilities of a standard PC fan motor.

Conducting a Speed Test:

A true speed test cannot be done with software like a PC monitoring tool. It requires direct, non-contact measurement. The standard method is using a tachometer or stroboscope.

    Tachometer: A laser or optical tachometer is pointed at a reflective piece of tape placed on the fan's hub. The device emits a beam of light and counts the number of reflections per second, directly calculating the RPM. This is the most common and accurate method for field testing.

    Stroboscope: A strobe light is shined on the fan. The frequency of the strobe is adjusted until the fan blades appear to stand still. At this point, the strobe frequency matches the fan's rotational speed, revealing the RPM.

What the Test Reveals:

Verifying that the fan can indeed reach and maintain 35,000 RPM under a 12V load is the first step. However, a full performance test would also measure:

    Airflow: Using an anemometer in a calibrated wind tunnel to measure the immense CFM output.

    Static Pressure: Measuring its ability to push air against resistance.

    Power Draw: At this speed, the fan will draw several amps of current, far more than a motherboard header can supply. It must be connected directly to the PSU via a Molex or SATA power connector, often through a dedicated controller.

    Noise Level: The acoustic output will be extreme, likely exceeding 70-80 dBA. It is a piercing, high-frequency whine that requires hearing protection.

In summary, a "speed test" of a 4028 35,000 RPM fan is a verification of its extreme engineering. It confirms its place as a component designed for a single purpose: moving a massive amount of air at any cost, where reliability and performance utterly outweigh concerns for noise or power consumption.