Read the guide: Vibration frequency explained
How to test a machine
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Step 1: Find the running speed (RPM) on the nameplate and type it in the RPM box. It's optional, but it lets the tool name the likely cause.
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Step 2: With the machine stopped, place your phone flat, screen up, on a solid part of the housing or base, close to a bearing. Tape it down if the surface is smooth or sloped.
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Step 3: Check that the phone and your hands are well clear of belts, pulleys, shafts, couplings and fans. Open Options under the Start button and set Stop after to 60 s.
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Step 4: Tap Start (on iPhone, tap Allow) and keep still for the 2-second "Hold still" step. Then start the machine and let it run at its normal speed and load.
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Step 5: When the test ends, stop the machine before you pick up the phone if it sits anywhere near moving parts. Tap Save image or Download CSV to keep the result.
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Step 6: Test again in the same spot and under the same load after each repair or once a month. A rising trend tells you more than one number.
What your result means
Your result lands on one of four levels. This page uses the machines and appliances scale, which is based on RMS velocity in millimeters per second (mm/s).
| Level | Range (RMS velocity) | What to do |
|---|---|---|
| Smooth | Under 0.71 mm/s under 0.028 in/s | Running smoothly. Save this result as a baseline to compare against later. |
| Normal | 0.71 to 1.8 mm/s 0.028 to 0.071 in/s | Normal for most small machines. Test again from time to time so you catch any change early. |
| Rough, check it | 1.8 to 4.5 mm/s 0.071 to 0.177 in/s | Worth checking. Look for loose mounting bolts, a worn belt or a coupling out of line, and plan a repair. |
| Too much vibration | 4.5 mm/s or more 0.177 in/s or more | Too much for a small machine. Find the cause before long running. Larger machines allow more, so check its size class too. |
How the machine vibration test uses your RPM
A machine vibration test is most useful when you know how fast the machine turns. The tool turns your RPM into a frequency by dividing by 60. A motor at 1,200 RPM turns 20 times a second, so its running frequency is 20 Hz. The tool then compares that with the main frequency it measured:
- Main shake at the running speed (1×). Likely imbalance: a heavy spot on the rotor, fan, pulley or impeller.
- Main shake at twice the running speed (2×). Possible misalignment between shafts, or looseness in the mounts.
- Neither. The shake may come from a belt, a part that turns at a different speed, or another machine nearby.
Phones deliver about 60 samples per second, so they can measure up to about 30 Hz, or 1,800 RPM. The exact limit for your phone is shown in the result details. If your machine’s running frequency is above it, the tool warns you. Here is how common motor speeds compare:
| Nameplate speed | Running frequency (1×) | 2× | Can a phone see 1×? |
|---|---|---|---|
| 870 RPM | 14.5 Hz | 29 Hz | Yes |
| 1,150 RPM | 19.2 Hz | 38.3 Hz | Yes |
| 1,750 RPM | 29.2 Hz | 58.3 Hz | Only just, on some phones |
| 3,450 RPM | 57.5 Hz | 115 Hz | No |
| 3,600 RPM | 60 Hz | 120 Hz | No |
Common causes and fixes
- Imbalance. Dirt caked on a fan or impeller, or a damaged blade or pulley. Clean it and replace damaged parts. A repair shop can balance large rotors.
- Misalignment. The motor and the pump or gearbox it drives aren’t lined up, often after a motor swap. A technician can align them with a laser or dial gauge.
- Looseness. Loose hold-down bolts, a cracked base, or one foot that doesn’t sit flat (called “soft foot”). Tighten the bolts, shim the foot, and repair the base.
- Belts. Worn, cracked or badly tensioned belts, or pulleys out of line. Belt problems often show up below the running speed. Replace and tension belts as the maker says.
- Resonance. A frame or base that shakes much more at one speed than at others. Stiffen it, add mass, or avoid running at that speed.
- Pumps. A crackling, gravel-like sound can mean cavitation. Check for a blocked inlet or a clogged strainer.
- Worn bearings. Early bearing faults are far too fast for a phone. By the time a phone notices, you’ll usually hear them too.
When to call a professional
Call a vibration analyst or a motor shop when the reading rises from one test to the next, when the machine runs hot or sounds different, or when it’s critical to keep it running.
What this tool can’t measure
- Fast vibration. Anything above about 30 Hz, including bearings, gear teeth, pump vanes and the 120 Hz magnetic hum of motors on US 60 Hz power. Fast vibration can show up as a false lower frequency. The tool then says “The main vibration may be faster than your phone can measure,” and the strength number may be off in either direction.
- Every part of the machine. It reads only the spot where the phone sits.
- Larger machines fairly. The result scale uses ISO 10816-1 class I zones for small machines up to 15 kW. For a medium machine (class II, 15 to 75 kW) the “check it” line is 2.8 mm/s instead of 1.8. The vibration severity chart shows every class. ISO 10816-1 has been replaced by ISO 20816-1, but these zones are still widely used as a rough guide.
- A certified number. A phone isn’t bolted on like a real sensor. For warranty claims, use a calibrated vibration meter.
Frequently asked questions
What RPM should I enter?
Use the speed on the nameplate, or measure it with a tachometer. On a belt drive, the motor and the driven shaft turn at different speeds, so enter the speed of the part you're testing. You can convert any speed with the RPM to Hz converter.
My motor runs at 3,450 RPM. Is this test any use?
Only for comparing. Its main vibration is at 57.5 Hz, well above what a phone can measure, so the tool can't name the cause. It can still show whether the shake changes over time if you test the same way each time.
What if I can't turn the machine off?
Place the phone, tap Start and let it run. The "Hold still" step then picks up some of the machine's shake and subtracts it, so the reading can come out too low or even say "No vibration detected." Compare only with other runs done the same way.
Is this a real vibration analysis tool?
It covers the basics: overall strength and the main frequency up to about 30 Hz. Professional analyzers read thousands of times a second from sensors bolted to the machine, and find bearing and gear faults a phone can't see. This is a good guide, not a certified measurement.
How is generator vibration different?
Most portable generators run at a fixed 3,600 RPM to make 60 Hz power, too fast for a phone to read directly. Inverter generators change speed with the load. Test on firm, level ground at the same load each time, and compare runs.
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