Tray oscillation amplitude is the main working parameter of a vibrating feeder: it determines how much material moves along the tray per unit of time. Unlike mechanical feeders with a fixed stroke, an electromagnetic drive lets you adjust amplitude smoothly without stopping the line — but that flexibility has a technical cost if it's tuned by feel.
What amplitude is and how it relates to capacity
Amplitude is the swing of the tray's oscillation, set by the voltage on the electromagnet coil through a control unit. The higher the amplitude, the faster and farther material is thrown forward on each cycle — and the higher the capacity. But the relationship isn't linear: for the resonant oscillating system most PEV drives are built on, peak efficiency is reached near the system's natural frequency, not at maximum coil voltage. See how amplitude is already factored in when sizing a model for the required capacity in our article on sizing a vibrating feeder.
Manual vs. automatic control
In a simple scheme, amplitude is set manually on the control unit and stays constant until the operator changes it — fine for a stable material with consistent properties. For material with variable moisture or particle size, or where a hopper blockage is a risk, automatic mode is recommended: a vibration sensor on the tray feeds the actual amplitude back to the control unit, which adjusts voltage to hold the setpoint regardless of tray loading. This also protects the drive from overload — current protection trips if amplitude drifts from normal. See the full model lineup on the control devices page.
Why you shouldn't just "turn it up to maximum"
Excessive amplitude is the most common cause of premature drive failure. At too high a voltage, the armature starts touching the electromagnet core on every cycle, producing a metallic knock, and the rubber elastic elements limiting armature travel wear out far faster than normal. This is sometimes mistaken for a drive fault, when the real cause is the setting — see a detailed breakdown of common failures and their causes in our article on common drive faults. Excess amplitude also increases dust generation and can create vibration transmitted into the structure the feeder is mounted to.
Matching amplitude to the material
| Situation | Tuning recommendation |
|---|---|
| Light bulk material (grain, fine granulate) | below mid-range amplitude — the material moves easily, excess amplitude just adds dust |
| Heavy coarse material (crushed stone, ore) | above mid-range — larger swing is needed to move bigger lumps |
| Caking, moist material | tune by trial together with a hopper agitator to avoid bridging |
| Startup under a full hopper | ramp amplitude up smoothly from zero, not a sudden jump to full power |
Common tuning mistakes
- Setting it once and forgetting it — moisture varies seasonally, and so does the optimal amplitude.
- Starting at full amplitude — instead of ramping up smoothly, especially risky when starting under a full hopper.
- Ignoring a metallic knock — that's a direct signal to lower amplitude and check the elastic elements, not something to "fix later".
- Compensating for drive wear by raising amplitude — if capacity has dropped because the elastic elements are worn, raising voltage only accelerates further wear instead of addressing the cause.
Not sure which amplitude and control mode suit your material? Describe your task via the request form and we'll help with tuning or select a control unit with automatic stabilization.