| 摘要 |
<p>The present invention relates to the measurement of a property, for example moisture content in a material subject to substantially transient presence in the region of a sensor. In a concrete mixer (1) the rotation of the mixing blades (8) causes the mix to lose intimate contact with a moisture content measuring sensor (9). This introduces noise, in the form of spikes, into the sensor output. The spikes adversely affect the accuracy of the moisture content measurement. The present invention solves this problem by sampling the output of the sensor (9) in the regions between the spikes. The timing of the sampling is triggered by the occurrence of a spike in the sensor signal, either directly by comparing the time derivative of the sensor signal with a threshold or indirectly, for instance by detecting the position of a mixing blade. A variety of samples may be taken between each pair of spikes and averaged to produce an output signal representing the moisture content of the mix in the mixer (1). In another embodiment, the invention is applied to sensing the moisture content of loaves (40) on a conveyor belt (41). The gaps between loaves (40) are detected and used to trigger sampling of the output of a moisture sensor (42).</p> |
