Abstract: A solid state sensor, micromachined in silicon, comprised first and second beams which can be optically excited into resonant vibration. The first beam is arranged to be acted upon by a diaphragm, so that the tension in it, and therefore its resonant frequency, is affected by the pressure applied to the diaphragm. The second beam is provided for temperature correction purposes, and to this end is positioned close to the first beam but free at one end, so that it is insensitive to the pressure applied to the diaphragm, while being subject to the same temperature variations as the first beam. Additionally, the second beam is positioned sufficiently close to the first beam that it can be optically excited simultaneously with the first beam via a single optical fibre.