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Nature | Vol.151, Issue.3822 | | Pages 135-135
Floatless Pump Control System
LONDEX, LTD., 207 Anerley Road, London, S.E.20, have introduced a patented system (“Lectralevel”) of floatless liquid level control, designed for automatically pumping out, filling or maintaining the liquid level in a container and employing a single mercury switch for controlling the pump motor starter. The pump suction pipe may be earthed and used as one side of the control circuit, the pressure of which (25 v.) is derived from a small double-wound transformer supplied from the power or lighting mains. The control circuit is completed through the liquid to be pumped, and only light insulation is required for the electrodes, which may be of ordinary galvanized wrought iron tubing. A shorter electrode terminating at the highest level of the liquid is connected direct to the relay, and when the level rises to this electrode the relay is energized and the pump motor started. A longer electrode is immersed in the liquid to the lowest required level and is connected to the relay by the same lead through a resistance of a few ohms, its function being to pass sufficient current through the relay to hold the latter closed after the level has fallen below the short electrode. When the liquid level falls beyond the longer (lower) electrode, the relay circuit is interrupted and the pump motor automatically stops. The motor is not restarted until the level reaches the shorter (upper) electrode, when the aforementioned resistance becomes short-circuited and sufficient current flows to actuate the relay. The relay employed is the Londex LQA, the mercury switch of which carries up to 20 amp. at 440 v. Where the liquid is under pressure or insulated electrodes cannot be employed conveniently, a patented automatic liquid level control device of the induction type is available wherein a float is employed to alter the magnetic conditions in two coils which respectively operate the relays at high- and low-liquid levels.
Original Text (This is the original text for your reference.)
Floatless Pump Control System
LONDEX, LTD., 207 Anerley Road, London, S.E.20, have introduced a patented system (“Lectralevel”) of floatless liquid level control, designed for automatically pumping out, filling or maintaining the liquid level in a container and employing a single mercury switch for controlling the pump motor starter. The pump suction pipe may be earthed and used as one side of the control circuit, the pressure of which (25 v.) is derived from a small double-wound transformer supplied from the power or lighting mains. The control circuit is completed through the liquid to be pumped, and only light insulation is required for the electrodes, which may be of ordinary galvanized wrought iron tubing. A shorter electrode terminating at the highest level of the liquid is connected direct to the relay, and when the level rises to this electrode the relay is energized and the pump motor started. A longer electrode is immersed in the liquid to the lowest required level and is connected to the relay by the same lead through a resistance of a few ohms, its function being to pass sufficient current through the relay to hold the latter closed after the level has fallen below the short electrode. When the liquid level falls beyond the longer (lower) electrode, the relay circuit is interrupted and the pump motor automatically stops. The motor is not restarted until the level reaches the shorter (upper) electrode, when the aforementioned resistance becomes short-circuited and sufficient current flows to actuate the relay. The relay employed is the Londex LQA, the mercury switch of which carries up to 20 amp. at 440 v. Where the liquid is under pressure or insulated electrodes cannot be employed conveniently, a patented automatic liquid level control device of the induction type is available wherein a float is employed to alter the magnetic conditions in two coils which respectively operate the relays at high- and low-liquid levels.
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