| 摘要 |
<p>Apparatus for controlling the heating of an electric element which repeatedly disconnects the electric element from the heating power supply and connects a resistor in series with the electric element and an electric potential across the series combination, when the voltage drop across the electric element is above a predetermined level, heating power is not reconnected to the electric element. The controller utilizes an adjustable time delay for providing the time period for which heating power is applied to the electric element. After each heating cycle the voltage drop across the electric element is monitored. The length of the monitoring cycle is controlled by a time delay and a voltage sensitive contact connected across the electric element. The monitoring cycle will terminate after a time delay, unless the voltage drop across the electric element is above a predetermined value, in which case it will continue until the voltage drop falls below the predetermined level. In other words when the electric element is heated its resistance increases thereby increasing the voltage drop across the electric element when a fixed potential is applied across the electric element and resistance in series. When the voltage drop across the electric element is above a predetermined value, the electric element remains isolated from the heating power supply.</p> |
