tube and rubber diaphragm are configured so as to decrease the amount of stretch of the rubber with increase of pressure thereby to decrease nonlinearity of the output electrical signal caused by nonlinearity in the stretching of the rubber a larger diameter of the pressure tube will yield less flexing of the diaphragm for a given change in pressure aperture 38 may also be suitably shaped so as to decrease effects of nonlinearity of the rubber flexing or stretching this entails shaping the aperture so as to conform to the profiles of the diaphragm 50 as the diaphragm expands with increase in pressure for example the shape of the profiles of the diaphragm on a plane perpendicular to the axis of light transmitted from the diode 40 may be plotted and aperture 38 shaped so that the area of the aperture blocked by the flexed diaphragm will have a more linear relation to the magnitude of pressure within pressure tube 46 further such nonlinearity and also hysteresis to which the rubber diaphragm is also subjected may be compensated electrically as will be described below illustrated in fig2 is a block diagram of an electrical circuit employing the pressure sensor and transducer of fig1 photosensitive resistor 44.