| 摘要 |
<p>An electrical circuit apparatus for detecting a rate of change of temperature outside of a predetermined range of rates of change of temperature comprising a bridge comprising first and second resistance branches connected in parallel, each branch comprising a first resistance connected in series with a second resistance. A meter is coupled between a first position between the first and second resistances of the first branch and a second position between the first and second resistances of the second branch. The meter is arranged to provide an output signal indicative of the voltage difference between said positions. A processor measures the output signal and stores a first measured value of the output signal at a first time and a second measured value of the output signal at a second time. The processor then compares the measured values and provides an alarm signal if the difference between said first measured value and said second measured value exceeds a predetermined threshold. The first resistance of the first branch and the second resistance of the second branch each comprise a respective heat sensitive element having a predetermined electrical resistance variation with temperature, the heat sensitive elements extending along the length of an elongate cable such that the voltage difference between said positions is indicative of the resistance of the heat sensitive elements. A method of detecting a rate of change of temperature outside of a predetermined range of rates of change of temperature using the electrical circuit apparatus is also provided. The electrical circuit apparatus is particularly suitable for detecting rapid reductions in temperature indicative of a leak from a container of liquefied gas.</p> |
