Liquid purification or separation – With alarm – indicator – register – recorder – signal or...
Reexamination Certificate
1995-01-23
2001-04-17
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
With alarm, indicator, register, recorder, signal or...
C210S096100, C324S439000, C324S443000, C340S603000
Reexamination Certificate
active
06217751
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monitor that tests the conductivity of water.
2. Description of Related Art
Municipal water can contain an unacceptable amount of impurities. Some end users use a reverse osmosis (RO) purification unit to remove the impurities from the water. RO units contain a membrane that captures the impurities while allowing “filtered” water to flow therethrough. Additionally, RO water purification systems may also include a pre-membrane filter and possibly a post-membrane filter to further purify the water. Over time the RO membrane and filters become less effective in removing contaminants from the water. If this condition is not detected and corrected by the replacement of the membrane and/or filter, the water purification unit will become inefficient and the quality of water will decrease to an unacceptable level. It is therefore desirable to have a sensor that can monitor the quality of water in a water purification unit.
U.S. Pat. No. 5,057,212 issued to Burrows discloses a water conductivity monitor for a water purification system. The purification system has a feed water probe within the unfiltered water and a filter water probe within the filtered water of the system. The Burrows monitor includes a button that is coupled to a battery and which provides a voltage to the probes when depressed by an end user. A comparator compares the ratio of the feed water probe voltage and filter water probe voltage, with a threshold value to determine whether the conductivity of the filtered water is below an acceptable level. The output of the comparator is latched into a light emitting diode (LED) to provide an indication of whether the water “passed” or “failed” the test.
The battery in the Burrows monitor is a DC voltage source which will induce electrolysis between the metal surfaces of the probes. Additionally, the probes will function as capacitors that store energy and distort the results of the test. To reduce the “battery” effect of the probes, the Burrows monitor includes a capacitor that creates a reverse flow of current through the probes. Unfortunately electrolysis of the probes still occurs. It would be desirable to provide a water conductivity monitor that does not have the disadvantages of the prior art.
SUMMARY OF THE INVENTION
The present invention is a water conductivity monitor that is controlled by a microcontroller which provides a pair of probe driving signals that are 180° out of phase. The monitor is connected to a feed water probe that is located within the unfiltered water of a water purification system and a filter water probe that is located within the filtered water of the system. The driving signals are provided to the probes to create a probe test signal. The filtered water test signal is a ratio of the voltage across the feed water probe and the voltage across the filter water probe. The driving signals are also provided to a resistor circuit which provides a threshold test signal. The test signals are integrated by an integrator circuit which is controlled by the microcontroller. The integrated test signals are compared by a comparator. The comparator provides an output signal to the microcontroller if the voltage level of the probe test signal is above the threshold test signal. The output signal is indicative of an unacceptable filtered water conductivity. The microcontroller illuminates an indicator light if the controller counts a predetermined number of output signals.
REFERENCES:
patent: 3838774 (1974-10-01), Dolan et al.
patent: 3990066 (1976-11-01), Malmgren
patent: 4201085 (1980-05-01), Larson
patent: 4806912 (1989-02-01), Clack
patent: 4847598 (1989-07-01), Tucci et al.
patent: 4851818 (1989-07-01), Brown et al.
patent: 4937557 (1990-06-01), Tucci et al.
patent: 5004535 (1991-04-01), Bosko et al.
patent: 5057212 (1991-10-01), Burrows
patent: 5096574 (1992-03-01), Birdsong et al.
Aquatec Water Systems, Inc.
Drodge Joseph W.
Irell & Manella LLP
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