@ Vibrating beam force sensors have a relatively low Q unless there can be prevented energy loss to the mountings at either end of the beam. This can be achieved by providing some sort of counterbalanced vibrating element; the available beam structures, which are all quite complex, involve balancing beams or counterweights that are in the vibrational plane of the 'main' beam, and flex in that plane. The invention provides a mechanically simpler but no less efficient beam structure by placing counterbalancing beams not above and below the main beam but on either side thereof.