| 摘要 |
<p>DIGITAL TEMPERATURE CONTROLLER A temperature control assembly for a centrifugal chemical treatment apparatus of the type having a temperature monitoring thermistor and a rotor heater. The heater is energized from a power source through a solid state relay. The thermistor is connected in a temperature Wheatstone bridge which delivers a voltage signal to a digital voltmeter. The digital voltmeter generates a binary output which is compared in a computer with a digital command signal from a keyboard unit. The binary computer is a programmed function of the difference between the keyboard digital temperature command signal and the voltmeter output. This computer output controls a variable duty cycle multivibrator stage which provides a relay-operating signal whose "on" time is in accordance with the difference between the keyboard command temperature and the digital voltmeter output signal. This operating signal is delivered to the relay via an over-temperature and failure detector receiving signals form the digital voltmeter. The relay is held open if forbidden signals are received, such as signals of incorrect polarity, over-range signals, signals resulting from a meter defect, signals resulting from a shorted or open thermistor, or the like. The same reference voltage is used for the digital voltmeter and the temperature Wheatstone bridge so that changes in reference voltage do not affect the voltmeter reading. The bridge is designed so that the bridge output in volts is equal to 1/100 of the temperature in degress Centigrade to facilitate display, over the specified design temperature range. The voltmeter is of a type providing forbidden signal outputs, including over-range, wrong polarity, overload, etc.</p> |
