| 摘要 |
PURPOSE:To permit exact temperature control even when use is made of a heater type sensor for an electric carpet which requires a comparatively large power consumption and a two-way power control element is made use of, by exploiting a phase change due to the capacity component of the sensor for a temperature signal. CONSTITUTION:A waveform that resistances 11-14 appropriately split and diodes 15 and 16 chip at a point A comes to have a phase theta decided by the resistance component of the impedance of the sensor 4, the capacity component and the resistances 11-14. A zerocross comparator 20 to detect a waveform at a zero volt converts the waveform at the point A into a waveform at a point B. With temperature rise inputted to a control means 6, the phase thetachanges, and a phase signal at the point B is obtained. The control means 6 as a method to measure the phase starts a timer counter at the rise of a signal from a zero volt signal circuit 8, and stops the counter at the rise or fall of the waveform at the point B in a temperature detection part 5. Then the reading of the counter becomes a temperature signal. The control means 6 energizes a relay driver 21 at the value and controls the conduction of a heater 4.
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