Nukit PC Fan Gauge: limited accuracy P-Q calculator

A free, low-resolution gauge for roughly measuring the properties of unlabeled, scavenged, or recycled 120mm and 140mm PC fans. Requires access to a 3D printer to make the test plenum and an Android or iOS phone capable of running phyphox.

How to measure

3D print your plenum. Download the plenum (testing box) and sliding cover for your fan size from the Plenum Builder. You will need a fan gasket; if you cannot purchase one, the Plenum Builder will let you 3D print a serviceable one in 90A Shore TPU.
Set up phyphox. On your Android or iOS phone, open phyphox, choose Pressure, press play, and turn on Remote Access. Note the IP address, and confirm you can open its page from another device's browser on the same Wi-Fi network (it will not work over mobile data).
Assemble the testing apparatus. Plug the fan into your power supply to verify that it works. Lay the plenum on a flat, stable surface with all ports covered and facing up. Place the phone inside the plenum. Attach the unplugged fan and gasket to the plenum with screws, ensuring that the fan is blowing outward. Make sure the sliding door opens and closes fully and is not blocked by the fan gasket.
Baseline (fan off). Read the pressure in the remote browser, from the phone running phyphox inside the plenum. The value cycles through a range; write down the center of that range. Don't wait for it to settle; it only keeps drifting.
Closed. Turn the fan on, wait ~10 s to reach full speed, then record the center reading.
1 port. Slide one port open to the debossed line, wait ~5 s, then record the center reading.
2 ports. Open the second port, wait ~5 s, then record the center reading.
Type the four readings into the fields below.

Keep the whole run under 30 seconds (baseline through 2 ports); the barometer drifts the entire time, so speed beats waiting for a stable number.

1Test fan size

Sets the size of the fan and plenum you are using. Create your plenum here.

2Baseline (fan OFF)

Ambient pressure (hPa)

not set

Read with the fan off, immediately before the other measurements so drift can't creep in. Baseline has to be reestablished for each test run.

3Readings (fan ON, suction)

Closed, all ports covered (hPa)

…

1 port open (hPa)

…

2 ports open (hPa)

…

Type the phyphox reading at each door position; ΔP vs baseline shows under each.

Advanced: calibration & comparison

4Calibrate the plenum (optional)

Reference fan, one you own with a Cybenetics curve

uncalibrated

Pick a reference fan, measure its readings above, then calibrate.

plenum constant (mm²)

Reuse a known plenum: type its plenum constant (its one calibration number). It also fills in here after you calibrate, so you can write it on your 3D printed plenum.

Optional: without it you still get an uncalibrated estimate. Calibrating with a fan in the same pressure class as what you plan to test corrects for your specific plenum.

5Fan under test, compare to Cybenetics (optional)

If the fan you're testing is in the database, pick it to overlay its Cybenetics curve

Leave on "Not listed" for an unknown fan; you still get an estimate.

Results

… mm H₂O

… Pa

est. dead-head (Q=0)

… m³/h

… CFM

est. free-air (ΔP=0)

Position	ΔP (mm H₂O)	ΔP (Pa)	open ⌀eq	flow (m³/h)	flow (CFM)

reference (calibration fan) your measured points (calibrated) fan-under-test (Cybenetics)

Reference fan data: Cybenetics Phi database, measured on a Long Win LW-9266. Reused with attribution per Cybenetics' terms, cybenetics.com. 1 mmAq = 9.807 Pa · 1 CFM = 1.699 m³/h.