| 摘要 |
The presence of contaminants on the lens (2) of a radiation temperature transducer is determined by providing a means of measuring the electrical resistance across the external surface of the lens of the transducer e.g. using electrodes on the surface of the lens or extending through the lens to emerge at its outer surface. Thus, at first installation or at the onset of an operation when the lens is known to be clean, a high resistance is measured across the surface of the lens and which becomes a datum. As contaminants build up on the lens a progressively lower resistance is measured and the arrangement can be such that either a signal is provided when contaminants have built up to a sufficient degree to generate an unacceptably artificially low temperature reading or the arrangement can be such that an automatic compensation factor can be added to the output from the transducer in accordance with the degree of build up of contaminants on the lens to ensure that an accurate temperature reading is maintained irrespective as to the degree of build up of contaminants. |
