Fan Test System, SPCR 2010

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There are two parts in our fan testing system. One part concerns audio measurements, the other involves cooling performance.

A. Audio Instrumentation and Resources (fully detailed in New Audio Test Gear, SPCR 2008) -- Our audio measurement tools are now far more sophisticated than before; it is SPCR's anechoic chamber and 9dBA-capable instrumentation. We can assess not only the SPL of a fan at different speeds, but also its frequency spectrum, so that tonal peaks can be identified and visualized.

ACO Pacific 1" diaphragm capsule mic with adapter on 1/2" preamp.

SpectraPlus screenshots.

M-Audio FireWire 410 atop M-Audio Tampa digital mic preamp.

B. Fan Test Gear -- Our latest airflow measurement device (anemometer) is by far the most accurate of the handful that we've acquired over the years. It is used not as a primary tool, however, but a secondary one. Our approach this time around is not to be concerned about airflow per se, but its thermal effects in a cooling system. CFM is relegated back to its original place when we first began assessing fans years ago: Mostly a point of note. Our most important measured parameter is temperature rise, not by itself but plotted against SPL.

  • i7-1366 CPU die simulator with embedded T-type Thermocouple wire
  • Mastech 6030D DC Regulated Power supply, 0-64V/3A
  • Custom built 0-12VDC Regulated Fan Controller
  • Kanomax 6803 Anemometer
  • Mannix DT8852 Dual Input Thermometer (K, J or T Thermocouple input)
  • High accuracy general purpose Multimeter
  • Laser digital tachometer by Neiko Tools USA
  • Calibrated electronic strobe light (alternate tachometer)
click for large image
This is our fan testing setup as of May 2010.
(Cick on image to enlarge.)

The i7-1366 CPU simulator, with T-type thermocouple wire embedded. Blue wires are used to power the heater coil in the copper block. The mounting block is a piece of phenolic resin (like Bakelite), which has high heat insulation qualities.

A Thermalright Ultra 120 Extreme heatsink is employed. It has roughly middling airflow impedance (resistance to airflow), and an excellent mounting system that ensures highly consistent pressure from one heatsink sample to the next, from one installation to the next. IC Carat Diamond thermal interface material was used between copper block and heatsink base to ensure maximum heat transfer.

This is the casing of a Shuttle Zen PC, gutted to squeeze in an FSB 300W ATX12V PSU and a Sunbeam 4-channel fan controller. The Sunbeam is unusual in that it allows the voltage to be varied from maximum to 0V. The 12V output of the PSU has been tweaked up to nearly 13V, in order to compensate for the voltage drop through the fan controller. The fan in the original PSU has been removed; it is not needed for the tiny loads of 12VDC fans. A separate multimeter is used to set fan voltage.

A Mannix DT8852 Dual Input Thermometer keeps track of temperature at the top of the simulator CPU die, and of the intake air 6" in front of the fan; the difference between these two temperatures is key. A Mastech 6030D DC Regulated Power supply can provide up to 64V at 3A. 137W was chosen to be the standard load. The calibrated strobe is one of the several tools used to measure fan RPM. An infrared tachometer is another.

The Kanomax 6803 Anemometer came supplied with a super low friction calibrated Pacer 275 vane probe. This is a high precision tool; the tiniest bit or airflow is enough to get the vane spinning. Airflow is measured in FPM (feet/minute) directly at the intake side of the fan, while it is mounted on the heatsink. The highest sustained value is recorded for each speed.

The foam harnesses used in earlier fan test are still used for acoustic measurements and recordings. We tried doing this while the fan was mounted on the heatsink, but there are just too many interactive results caused by the rattling or buzzing of the fins on the heatsink. The foam harnesses minimize such effects; you can say, generally, that the recordings of the fans represent them at their best or quietest... although in a few odd exceptions, some fans sound better mounted on the heatsink.

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