Aquatronics, Inc.

Systec Corporation

Mario A Tucci

George K Sutherland

A monitor and indicating circuit for use with a reverse osmosis filter for signaling the need for servicing of the filter comprises first and second conductivity cells respectively located in the water inlet and outlet pipes of the filter. An AC signal of a predetermined frequency and amplitude is used to drive an op amp whose input resistance comprises the outlet conductivity cell and whose feedback impedance comprises the inlet conductivity cell. Normally, the resistivity of the outlet conductivity cell is substantially larger than the resistivity of the inlet conductivity cell, assuming that the filter is functioning properly. As the ROF fails, the resistivity at the outlet approaches that at the inlet thereby increasing the gain of the variable gain amplifier. The output from the variable gain amplifier is then peak detected and applied to a comparator where it is compared to a predetermined reference voltage. If the output from the peak detector remains below the comparator's reference, the logic means operates to cause a green LED to be illuminated. However, as the filter becomes used, the gain of the operational amplifier approaches unity and the comparator will produce a signal causing a red LED to be lit.

Monitoring and indicating circuit for reverse osmosis filter

A signal responsive circuit especially adapted for use in a water treatment system for signaling the need for regeneration of an ion exchange resin bed or the replacement of a particulate filter medium. A series of three electrodes are disposed in the water treatment medium in longitudinally spaced relation along the direction of flow and an alternating current signal drives the center-most electrode. The two outer electrodes are coupled as inputs to first and second operational amplifiers having asymmetrical gain characteristics. When the effective resistance between the center electrode and the two outer electrodes are equal, which is the condition prior to the movement of the hardness front or contamination front to the location of the electrodes, a first signal output condition exists. However, when the resin bed or filter medium becomes 'exhausted' to the point where the hardness or contamination front moves to a point between the center and upstream electrode, the signal output condition reverses state and can be used to trigger regeneration or replacement of the medium. The use of an alternating current drive signal obviates problems relating to electrode contamination or erosion. Further, an AGC circuit is utilized to ensure proper operation under variations in ambient conditions, such as temperature changes in the medium. A low pass filter also is effective to render the system less subject to short-duration transient conditions.

Water treatment regeneration system incorporating alternating current

A method and apparatus for initiating the regeneration cycle of an ion exchange resin type water softener based upon the movement of the 'hardness front' through the resin bed as water being treated is passed therethrough. Electrical probes are provided at predetermined longitudinally spaced locations and the difference in potential between the probes is measured, as is the rate of change of this potential with respect to time. It is found that as the hardness front passes between the probes, a detectable change in potential occurs which may be applied to an electronic circuit for generating a control signal which may initiate the regeneration cycle of the water softener subsequent to the arrival of the hardness front in the zone between the probes.

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Saint Paul, MN, United States of America

Mario A Tucci