{"id":4303,"date":"2026-09-07T09:00:00","date_gmt":"2026-09-07T16:00:00","guid":{"rendered":"https:\/\/www.rbdinstruments.com\/blog\/?p=4303"},"modified":"2026-09-06T09:12:39","modified_gmt":"2026-09-06T16:12:39","slug":"testing-fan-airflow-on-cooling-fans-on-a-phi-aes-or-xps-system","status":"publish","type":"post","link":"https:\/\/www.rbdinstruments.com\/blog\/testing-fan-airflow-on-cooling-fans-on-a-phi-aes-or-xps-system\/","title":{"rendered":"Testing fan airflow on cooling fans on a PHI AES or XPS system"},"content":{"rendered":"\n

The electronic racks in many of the older Physical Electronics \/ PHI surface analysis systems use fans to provide airflow to cool the electronic units and card rack boards. As part of the yearly preventive maintenance on these systems the fans should be inspected and replaced as needed.<\/p>\n\n\n\n

A dead fan is easy to spot as the blades are not spinning at all. But for the fans that are spinning, how can you determine where the fan is providing good airflow?<\/p>\n\n\n\n

There is an effect that we have all seen called the Wagon Wheel Effect.  The phrase comes from seeing wagon wheels that appear to be spinning backwards or even not spinning at all in old west movies and TV shows.  What it is really is just the frame rate of the movie or TV camera and how it syncs to the spinning wheel.  You can see this effect on the card rack fans due to the 50 or 60 Hz fluorescent or LED room lights and even in outdoor steady sunlight due to the few milliseconds that the human brain needs to detect motion.<\/p>\n\n\n\n

What this means is that you can\u2019t be 100% sure of how fast a fan is spinning just by looking at it.  An Anemometer is a way to measure the velocity of air and is a great way to get a relative answer as to how much airflow the fan is putting out. For this blog post I purchased a TOPTES TS-301 on Amazon for about $30.00<\/p>\n\n\n\n

TopTes TS-301 Digital Anemometer, Wind Speed Meter with 2.26-inch Big Backlight LCD Screen, Air Flow Meter for Sailing Surfing Drone Flying RC Plane Golf Shooting HVAC<\/a><\/p>\n\n\n\n

This air speed measuring device is equipped with easily rotatable fan blades and measures air velocity in 6 units: Feet per minute (ft\/m), Feet per second (ft\/s), Miles per hour (mph), Knots (knots), Kilometers per hour (km\/h), Meters per second (m\/s) Value of wind velocity x10.\u00a0<\/p>\n\n\n\n

For this blog post we used km\/hour to get a relative fan air speed measurement. In the picture below we get a measurement of 15.3 km\/h on a working fan.<\/p>\n\n\n\n

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