Just like immersion vibrators, external vibrators, as the name suggest, vibrate the concrete externally. The vibrator is fitted externally to the concrete forms to vibrate and consolidate the concrete.
They are often used on construction sites and in precast applications to obtain high quality, off form finishes. External vibrators are available in electric and pneumatic variants. External vibrators are ideal for precast as they can be fitted to precast moulds and can be used to ensure consistent consolidation every pour.