GB1395493A - Apparatus for controlling the conductivity of an electro lyte - Google Patents

Abstract

1395493 Induction conductivity control DEFENCE SCRETARY OF STATE FOR 11 July 1972 [16 June 1971] 28189/71 Heading G1 [Also in Division C7 and G3] The conductivity of an electrolyte which may be used in electro-chemical machining is maintained within desired limits by automatically controlling valves in a heat exchanger to heat or cool the electrolyte. The electrolyte temperature may also be regulated automatically. As shown, a conductivity cell includes two windings whose coupling depends on the conductivity of the solution. A squarewave signal is applied to one of the windings, and the resultant output signal from the other winding is rectified to produce a signal indicative of conductivity. This signal is supplied to a meter and chart recorder and is also compared with desired pre-set limits in a Schmitt trigger circuit PCB2 to energize triac 1 or triac 2 if the conductivity is too high or too low. The triacs operate motorized valves controlling the admission of steam or water to a heat exchanger controlling the temperature of the electrolyte. A resistance probe may be employed to sense the electrolyte temperature, and is connected in a bridge circuit to produce output signals if the temperature lies outside a pre-set range. These signals may operate visual and audible alarms and also indicate that salt or water should be added to the electrolyte solution. By changing over switches S2B, S2C the temperature measurement can be used to control the heat exchanger valves while the alarm arrangement responds to the conductivity signal. The valves can be disconnected for testing by driving independently of the triac circuits.