| 摘要 |
<p>The temperature measuring device, is partic. for central heating systems. A pair of temperature dependent resistors are clamped to the flow and return pipes of a heating system. Constant current sources supply current to the resistors, and the voltage developed across them is fed to one input of two comparator circuits. The other input of the comparators is connected to a sawtooth generator which is, in turn, controlled by a flow meter and switch arrangement. the sawtooth generator also controls a clock pulse generator. The outputs of the comparators and the clock pulse generator arefed to an AND gate and thence to a display device. The output frequency of the clock pulse generator varies linearly with variation of the measuring resistors.</p> |
