This may look like an ordinary sledge hammer, but in fact,
it is a special one for the vibration
testing of small structures.
Look carefully and you can see that it has a special head
on one end. This can be changed to vary the nature of the
force when the hammer hits against a surface.
The hammer head also contains special electronic equipment
called a "load cell" that measures the force. An
electrical signal from the load cell runs along the cable
to the monitoring and recording equipment.
This picture shows the hammer being used for the vibration
testing of a flood gate on top of a dam.