| 摘要 |
<p>An optical sensor arrangement comprises a light emitting diode (10) which is connected to a light detector (20) over a light connection such as a fibre optics fibre (15), the attenuation of the light connection depending on a variable to be measured. The fibre (15) may be provided in the vicinity of a vortex shedding flowmeter and is bent by the passage of vortices past the fibre. Bending the fibre (15) causes attenuation of the light signal from the light emitting diode (10) to the light detector (20). The light emitting diode (10) is powered by a pulse generator (U6 etc). which supplies the diode with low-duty cycle, high-current pulses. The resulting detected pulses are amplified, sampled and held (U1, U3) to obtain peak values for each pulse. The detected pulse is suppressed by a feedback circuit portion (U2b, U2c) which is activated only after each low duty cycle high current pulse. The detected peaks are utilised (U8c) to generate a square wave which is used as a measurement of the variable, in particular the passage of vortices in a vortex shedding flowmeter.</p> |
