MXPA06005095A - Service initiation and regeneration control using impedance ratios - Google Patents

Abstract

An apparatus and method for determining the end of a service step and the duration of a brine/slow rinse step in a water conditioner having a bed of ion-exchange material. A sensor probe and a reference probe are positioned in the bed of ion-exchange material vertically displaced from each other. Voltage from each of the probes are monitored over a plurality of time intervals. When the percent increase in the impedance ratio exceeds a pre-specified value the end of a service step is identified and a regeneration cycle is initiated. During the regeneration step, the rate of change in the impedance ratio of the sensor probe to the reference probe is calculated and used to detect two peaks in the rate of change of impedance ratio between the sensor probe and the reference probe, followed by terminating the brine/slow rinse step after both peaks have been detected.

Description

CONTROL OF INITIATION AND REGENERATION OF SERVICE THROUGH THE USE OF IMPEDANCE INDICES FIELD OF THE INVENTION This application relates to control sequences for automatic water conditioning products. More specifically, it relates to a method for determining the end of a service cycle and the duration of the brine / slow rinse cycle during the regeneration of an automatic water conditioner and the apparatus employing the method.

BACKGROUND During hard water treatment, a bed of ion exchange resin or other material in a water conditioner removes the calcium and magnesium ions from the water and replaces them with sodium ions. As the hard water passes through the bed, it exchanges these ions of hard water with sodium in the first soft resin that is found, which creates a wave of ion exchange activity called the reaction zone. The bed becomes ineffective to soften and must be regenerated periodically when the amount of available sodium is finished and the ion exchange material is saturated with calcium and magnesium. The water treatment is then suspended while the ion exchange material is regenerated in a multi-step process to discard the calcium and magnesium ions from the resin and restore the sodium level.

A series of steps is used to replace the hard water ions with sodium ions, to make the ion exchange material active again for water conditioning. Usually, the bed is first subjected to a reverse wash, reversing the flow of incoming water, to remove sediment and loosen the bed. The bed is then contacted with a downstream brine solution, by means of which the ion exchange material takes sodium ions from the highly concentrated brine solution and displaces the calcium and magnesium ions in the brine. and they are discarded. When an optimum amount of brine has been delivered, the rinsing continues until virtually all traces of the brine solution and the unwanted ions of hard water in it are discarded from the bed. After being rinsed to remove the brine residues, the bed has been restored to its sodium state, known as soft resin and then returned to the service by treating hard water.

The preparation of the brine solution usually takes place in a brine tank that is kept apart from the resin tank. The brine tank, which contains a salt supply, is filled with a measured amount of water to form a solution saturated with salt. The salt supply must be periodically replaced because it is finished after several regenerations. If the salt level is too low to make a brine solution with a given concentration, there will be an insufficient level of sodium to boost the exchange of calcium and magnesium ions and the resin will not effectively treat hard water when it returns to service .

More modern water conditioners such as water softeners and the like use electronic controllers to make calculations, monitor the sensors, direct the timing and control valves during the various steps of the process. Some newer and more sophisticated water conditioners use electronics to program the next regeneration cycle based on one or more of their inputs. The data entries include, for example, information on the chronometers, flow meters, historical data stored on water use and the like. Many control sequences have been developed to determine the sequence and duration of the various steps required during the regeneration of a water conditioner. In a simple sequence of regeneration, each step has a fixed time, regardless of the degree of saturation of calcium and magnesium in the resin. To guarantee that the bed is completely regenerated, the duration of each step should be at least the time necessary for that step of the process, assuming that the resin was completely saturated with hard water ions at the beginning of the regeneration. Using this technique, the same amount of time and brine is used regardless of whether the resin is saturated at 10%, 40% or 90%, resulting in a loss of time and salt when the resin is less saturated with ions of hard water.

When designing a regeneration control sequence, it is preferable to minimize the duration of the regeneration process for a number of reasons. While the unit is being regenerated, it is not in service to soften water. Most consumers want their water conditioner to provide mild water at all times, even very late at night or very early in the morning. Reducing the amount of time the unit is not in service decreases the likelihood that soft water will not be available when needed. Using less salt and water for regeneration reduces the cost of operation. There is also the need to minimize the amount of brine discarded from the water conditioner into the environment. Reducing the length of the brine cycle helps minimize the use of brine, and therefore reduces the impact on the environment.

In U.S. Patent No. 5,699,272, the duration of a rinse cycle is determined using the difference in voltages between a sensor probe and a reference probe looking for three different states. The first state occurs when the bed is completely surrounded by sodium ions at the start of the brine / slow rinse cycle, indicating that the brine has filled the bed. While the brine supply stops and the rinse water washes away the sodium, a front advances in the bed with a high concentration of sodium in front and a low concentration of sodium behind. The second stage occurs when the front is between the sensor probe and the reference probe, indicating that the brine solution is being flushed from the bed. The third stage occurs when the front has passed the reference probe, both sensors are in the low sodium solution, which indicates that the rinsing can be completed.

None of the known regeneration schemes of the prior art consider the effects of manufacturing variations or failures of probes or sensors over time. When the differences between the two probes or between a probe and a reference value are used to determine the end of the cycle, the changes can produce the same difference in values as the pass of a front. In addition, the sensors can be covered with sediment, scale, oxide deposits or other faults, which makes the sensors less sensitive over time to the changes around them. As the sensitivity of the sensor decreases, the differences in the readings become less precise and impact the ability to correctly detect the start or end of a step of the process. As a result, the unit may fail to recognize the need to regenerate or may regenerate more frequently than necessary.

In addition, the plating of the sensors causes the comparator to give the signal for a premature regeneration because the impedance increases steadily. As a result, the reserve capacities increase and the efficiency of the softener decreases, which leads to a waste of water and salt. In addition, the prior art employs sensor readings in fixed comparisons or compares them with predetermined values. It is difficult to compensate for a replacement sensor that gives slightly different impedance readings due to differences in manufacturing.

The available computer programs can not take into account sensors that have been plated as a result of years of exposure to minerals in a running water environment. The fixed or predetermined values can consider initial states of some of these variables, but can not compensate for changes that occur over time.

Thus, there is a need for a method to determine the duration of the steps in the process cycle of a water conditioner that maintains its accuracy over extended periods of time. The method must accurately determine the completion of the service step or a brine / slow rinse step in spite of faults or replacement of one or more sensor probes.

SUMMARY OF THE INVENTION These and other problems are solved with the present method to determine the duration of a! minus one of the service steps and the brine / slow rinse step in a process cycle for a water conditioner with bed of material for ion exchanges. The method includes placing a sensor probe and a reference probe in the bed of the ion exchange material vertically separated from each other, with the sensor probe upstream of the reference probe. The voltage of each of the sensor probe and the reference probe are monitored and the impedance ratio of the sensor probe compared to the reference probe is calculated over a plurality of time intervals. During the service step, when the percentage difference between the current impedance ratio and the minimum impedance ratio exceeds a first minimum increment, the completion of the service step is programmed and the brine / slow rinse step is initiated. During the brine / slow rinse step in the regeneration cycle, the voltage of each of the sensor probe and reference probe is monitored and a ratio of change in the impedance ratio of the sensor probe to the probe is calculated. reference. The calculation of a rate of change in the impedance ratio allows the detection of a minimum and maximum point during the brine / slow rinse cycle. The first peak in the rate of change of the impedance ratio is detected when the impedance ratio is minimal. The monitoring, calculation and detection of the steps is repeated until a second peak is detected. The second peak in the rate of change of the impedance ratio is detected when the impedance ratio is maximum. The brine / slow rinse cycle is terminated after both peaks have been detected after a specified wait time.

A water container having a material for ion exchange includes a sensor probe placed in the bed and a reference probe placed in the bed under the sensor probe. A circuit is configured to monitor the voltage of each of the sensor probe and the reference probe during a plurality of time intervals. The apparatus also includes a controller configured to monitor the voltages of the sensor probe and the reference probe and calculate the impedance ratio of the sensor probe compared to the reference probe. The calculated impedance ratio is used to determine the duration of the at least one service step and the brine / slow rinse step. If in the service step the controller also calculates the percentage difference in between the current impedance ratio and the minimum ratio of cycle impedance, and programs the regeneration if the percentage difference exceeds a first predetermined value. If the process cycle is in the brine / slow rinse step, the controller detects a peak in the rate of change of the impedance proportions, repeats the monitoring and calculation steps until a second peak is detected and the step is completed of brine / slow rinse when both peaks are detected.

The water conditioning apparatus and the method for operating it do not have many of the disadvantages of the prior art. An important feature of the present water softener system and method is that the detection of process events is based on a relative proportion of impedance, as opposed to an absolute ratio of impedance. The use of relative mpedance proportions eliminates the effect of the factors that change the sensor readings by a multiple of the actual reading. In addition, we also measure the degree of change in the relative proportion of impedance as opposed to an absolute and predetermined ratio of impedance. The above helps to compensate for problems that present several manufacturing differences, field conditions and the inevitable "aging" of the sensors to be placed in an environment of running water for years.

DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 is an elevational view of a system for softening water of the type suitable for use with the present invention, with portions cut away for clarity; Figure 2 is a circuit diagram for a Wheatstone bridge circuit; Figure 3 is a flow chart of a process for determining the end of a service step; Figure 4 is a flow chart of a process for determining the first peak in the regeneration step; and Figure 5 is a flow chart of a process for determining the second peak and the end of the regeneration step.

DETAILED DESCRIPTION OF THE INVENTION Water conditioners that use sensors in a bed of material for ion exchange to indicate regeneration are well known, as are the U.S. Patent Nos. 4,257,887; 4,299,698; 5,699,272 and 5,751,598 to Culligan International Co., each of which is hereby incorporated by reference in its entirety.

Referring now to Figure 1, a system for conditioning or water conditioning, generally designated 10, has a bed 14 of an ion exchange material 16 capable of receiving hard water ions of hard water during a softening step and release the ions of hard water during a regeneration step. The conditioner has a controller, generally designated 20, to control the steps of the program cycle which, among other things, initiate and complete the regeneration steps to replenish the sodium content of the ion exchange material 16 when it is finished. For purposes of this discussion, the bed 14 has an upper portion 22 that is defined as the upstream portion of the bed or the portion of the bed that has the first contact with the hard water as it flows through the bed of ion exchange during the service step. The bed 14 has a lower part 24 which is defined as the downstream portion of the bed or the portion of the bed that has the last contact with hard water as it exits the ion exchange bed during the service step. Any directional references should be interpreted as if the system for water conditioning 10 was oriented as illustrated in Figure 1.

The conditioner 10 includes a frame or tank 26 that holds an amount of the material for ion exchange 16. The ion exchange bed 14 includes a bed of any material 16 that removes hard water ions as is well known to those skilled in the art. . Resins for ion exchange are the preferred material for ion exchange 16. Generally, the ion exchange resin 16 is a polymeric drop with functional groups attached to the polymer to perform the function of the ion exchange. The ion exchange takes place in the cation or the anion, depending on the functional groups attached to the polymer. Zeolites are also known as materials for ion exchange 16. As untreated water rich in heavy water ions, such as calcium and magnesium, passes through bed 14, the hard water ions are exchanged for water ions. soft water, like sodium. In the example presented below, the material for ion exchange 16 is discussed in terms of the resin for ion exchange; however, the use of other materials for ion exchange is also contemplated for use in all specimens.

When the conditioner 10 is designed for home use, the frame 26 is usually a single unit, however, other suitable conditioners 10 optionally have two or more parts constituting the frame. In the preferred specimen, the resin tank 26 is surrounded by a brine tank or salt chamber 32. Other conditioners 10 are known to have separate the resin tanks 30 and the brine tanks 32 (Figure 1). When it is necessary to have an uninterrupted supply of soft water, multiple resin tanks 30 may be employed so that one unit is softening while one or more are regenerating. For the purposes of the present invention, the frame 26 includes all of these individual units.

The water conditioner 10 also has a softening salt 34 in the salt chamber 32. Sodium salts, such as sodium chloride in pills, in a solid block or in granular form, are the most common softening salts 34, but any salt A solid capable of exchanging hard water ions, such as the potassium salt, is contemplated for use with this invention. Salts with high purity are recommended to prolong the time between salt additions and to reduce the amount of impurities that accumulate on the bottom of the water conditioner 10, but the purity of the salt does not directly affect the operation of the controller 20 or the conditioner 10 described herein. Water is added to the salt chamber 32 so that the softening salt 34 is dissolved, to make the saturated brine (not illustrated) to be used during the subsequent regeneration. The brine is kept separate from the hard water supply 36 and the material for ion exchange 16 while the softening takes place so that the brine does not contaminate the soft water and because the ion exchange between the resin 16 and the hard water would not occur in a efficient in the presence of brine. The brine only comes into contact with the ion exchange resin 16 during the regeneration step via a line 37 through a control valve 38 and an inlet 40.

Still with reference to Figure 1, during the softening, the controller 20 operates the valve 38 to allow hard water from the hard water supply 36 to flow into the resin tank 26 through the inlet 40 and the soft water comes out at through a tube 42 to an outlet 44 that supplies the soft water to the water system (not shown). Between inlet 40 and outlet 44, hard water comes in contact with the sodium-rich ion exchange resin 26, where hard water ions, including calcium and magnesium ions, are received by the resin and ions are released from the water. sodium in soft water. The soft water is discharged from the container 10 through the outlet 44. When the hard water enters the resin bed 14 a different interface emerges between the hard water and the spent resin 26 upstream of the bed and the soft water and the water. resin in sodium state current under the bed. This interface allows the controller 20 to measure and detect an increase in the relative proportion of impedance. When the resin 16 is saturated with hard water ions and the sodium or potassium ions are terminated, the resin is regenerated as described above. The spent brine is removed through a drain pipe 46.

The controller 20 initiates and controls the steps of the process cycle. For the purposes of this invention, the controller 20 includes at least a microprocessor or control unit with microcomputer 50 and a user interface 52. Some functions of the unit controller 20 include the synchronization of the softening and regeneration steps. and opening and closing the valves 38 as appropriate. The controller 20 can carry out other tasks as well. Most modern systems for softening waters include a microprocessor in the controller 20. It should be appreciated that the microprocessor 50 may have functions not specifically described in this application that are not part of this invention, even when performed by the same or similar equipment.

Preferably, the process steps are directed by the controller 20 by moving one or more of the control valves 38. In the preferred instance, the positions of the valve 38 determine whether hard water or brine flows into the resin tank. 26. Any electronic actuation valve 38 is appropriate for the valve, including solenoid valves or valves controlled by an electronically controlled rotating cam.

The process includes a number of steps. During the softening or service process, the hard water from the supply 36 flows into the resin tank 26, then to the tube 42 to provide soft water to the water source 44. At the end of the softening step, there is a reverse washing step by means of which the hard water enters the bottom of the tube 42 and flows upwards through the the bed 14, coming out at inlet 40 and going to drain 46. This step loosens the particles in bed 14 which have been compacted due to the gravity and downward flow of softening water, and also removes solid impurities that can get stuck in bed At the conclusion of the reverse wash step, brine is introduced into the bed 14 from the brine tank 32. The amount of salt 34 to be used to make the brine is entered into the controller 20 with the user interface, for example a keyboard or a touch screen. An appropriate amount of water is added to the salt 34 as determined by the controller 20. When the resin 16 is being regenerated, the control valve 38 is repositioned to drain the brine from the brine tank 32 and send it to the resin tank 30.

As the brine is pumped into the resin bed 14, it effectively surrounds the resin 16 with sodium ions. Due to the high concentration of sodium, equilibrium favors the replacement of hard water ions with sodium ions in resin 16, and allows the hard water ions to come out with the brine. A first front emerges between the upstream brine and the hard water downstream. After coming into contact with resin 16, the spent brine is discharged into drain 46 and the slow rinse begins.

When the brine is spent, the slow rinse begins, directing the hard water to enter the top of the resin tank 30 to wash the remaining brine in the bed 14 and begin softening. A second front or interface drives the soft water upstream and the spent brine downstream. When all the brine has been discarded from the resin tank 26, the unit is returned to service generating soft water. A third front is created as the resin 16 in bed 14 progressively gives up the sodium ions and exchanges them with hard water ions. This third front is characterized by hard water upstream and soft water downstream from the front.

The controller 20 is regulated by a set of instructions, preferably in the form of a computer program. Preferably, the computer program is preloaded in the memory of the microprocessor 50 at the point of manufacture. As an alternative, the set of instructions can be loaded into fixed memory, such as read memory only for installation in the microprocessor 50. Any method for electronic storage of the instructions is appropriate as long as the instructions are readily available to the controller 20 when it is in use.

The bed 14 of the water conditioner 10 also has placed inside it a reference probe 54 and a sensor probe 56, vertically spaced from each other. Any probe 54, 56 that is capable of indicating a change in resistance in the material for ion exchange and the surrounding water is useful. Typically, each of the probes 54, 56 has at least one pair of separate electrodes, and preferably includes two pairs of separate electrodes. A favorite probe is AQUASENSOR from Culligan International (Northbrook, Illinois).

A sensor holder 58 holds the probes 54, 56 in a fixed position within the bed 14. Between the resin tank 26 and the controller 20, a conduit 60 carries the electrical signals from the probes 54, 56 to the controller. The placement of the reference probe 54 at a particular position is not necessary; however, preferably the probe is placed near the bottom 24 of the bed 14 to make it easier to calculate when the ion exchange front or the interface of the medium will reach the bottom of the bed. The sensor probe 56 is placed closer to the top 22 of the bed 14 than the reference probe 54 so that the sensor probe is upstream relative to the reference probe. Probes 54, 56 are also separated horizontally as an option. An interface of the medium occurs where there is a change in the liquid medium that moves through the bed, such as brine, hard water or soft water.

Optionally three or more probes 54, 56 are used in the resin bed 14 to more accurately determine the position of the ion exchange front or media interface. When the circuit analysis, described below, is applied to the probes 54, 56 two by two, the progress of the ion exchange front or the interface of the medium through the bed 14 can be monitored closely. When two or more probes 54, 56 are used, the vertical or horizontal separation between them need not be uniform.

Referring now to Figure 2, preferably a Wheatstone bridge is used to monitor the voltage of the sensor probe 56, VSTnsor and reference probe 54, Vreference, in each of the plurality of time slots. The bridge has two fixed resistors, Ri and R2, with voltages VRI and VR2, respectively and impedances ZRI and ZR2, respectively. If Ohm's law is applied to the sensing leg of the Wheatstone bridge 62: sensor sensor \ / where I is the current through the circuit. In a circuit, the equation for impedance is given by: where R is the resistance of the circuit, XL is the inductive reactance and Xc is the capacitive reactance. For a pure resistance, as are the reference resistors in the circuit board, XL and Xc are both equal to 0, which reduces the equation Ill a: Z = R (IV) by applying Ohm's law, equation II can rewrite as follows: The current in the circuit can be calculated as: / = ^ (VI) Kl Since the sensor probe and the fixed resistance Ri are in series, the voltage in Ri is equal to the difference between the voltage of Total supply, VSUppiy, supplied to the circuit and the voltage in the sensor probe 56, Vsensor- Therefore, VRl = (VSupply ~ Vsensor) (VII) Substituting the equation V in the equation VI: j __ V Supply - V sensor (\ J \\ \) Rl Substituting the equation Vlll in Ohm's law results: 7 = 7? V Ji V sensor sensor 1 (IX) Supply sensor) Applying the same equations to the reference portion of the Wheatstone 62 bridge results in: ry p j 'reference I / Y \ fe ference ~ K2 X 1 ~ XX ~ X- 7 f V ^ I Supply reference' J Using equations IX and X to calculate the ratio, and using the established logic of the Wheatstone 62 bridge, the impedance index is: In a preferred issue, the fixed resistors Ri and R2 on the Wheatstone bridge 62 are 200 ohms for Ri and 215 or 226 ohms for R2. The resistance values may vary to suit the application. The sensor 56 and reference 54 probes are variable resistors. The controller 20 supplies a voltage of 2.5-5.0 to the circuits of the Wheatstone bridge. With reference to the voltage values, Vsensor and Vreference, and the two fixed resistors Ri and R2 in the Wheatstone bridge circuit 62, the microprocessor 50 can employ a computation program to calculate the impedance ratio of the sensor probe 54 with the reference probe 56.

The passage of a front is detected by comparing the impedance of the reference probe 54 and the sensor probe 56. The term "front" is intended to include the reaction zone as well as any interface between the hard water, soft water and brine. . As the environment around the probe changes, probes 54, 56 produce various voltages depending on whether they are surrounded by hard water, soft water or brine. The electrical signal variants of the probes 54, 56 are monitored in the controller 20 and used to determine when the service step or the brine / slow rinse step should be terminated. The monitoring occurs during a plurality of selected time intervals so that none of the fronts passes through any of the sensors 54, 56 without being detected. The selection of the time interval depends on the flow rates of the liquid and the vertical separation of the probes 54, 56. Preferably, the time intervals are regular, although the microprocessor 50 optionally suspends monitoring during periods when it is not expected no front. The preferred time interval is 30 seconds.

When the service step begins, both probes 54, 56 are in soft water and material for ion exchange 16. As the softening begins, the hard water travels through the resin bed 14, exchanging hard water ions with the sodium ions related to resin 16. Hard water ions are exchanged first with the sodium ions with which they come into contact, creating a front that moves through the bed 14 in the direction of the water flow. The water upstream from the front is hard water and the water downstream from the front is soft water. The impedance index will be approximately constant and equal to one, until the ion exchange front reaches the sensor probe 56. As the ion exchange front passes through the sensor probe 56, the material for ion exchange 16 changes from a state regenerated to a spent state and the surrounding water changes from soft water to non-soft water. At this point the reference probe 54 is still in soft water and regenerated resin. As a result, the impedance index increases.

When compared to the minimum impedance for the current cycle, a peak is detected when the first predetermined increase in the impedance index is given. The values of the same process cycles are used to determine the increase to minimize the effect of external variations that include a change in the supply of untreated water, replacement of a probe and / or faults in probes 54, 56 of previous cycles .

The first predetermined increment in the impedance index is any value that indicates that the difference between the current impedance index and the minimum impedance index for that cycle approaches the maximum. The exact values of the first predetermined increase are determined by characteristics of the probes 54, 56, the fixed resistors in the circuit board and the tolerance to premature regeneration. Increases of approximately 5% to approximately 15% are especially useful when using the preferred AQUASENSOR probe. More preferably, the first predetermined increase in the impedance index is from about 7% to about 8%.

If the increase between the minimum impedance index and the current impedance index exceeds the first predetermined increment for a minimum period of time, then the completion of the service step is carried out immediately or according to a programmed time delay. Preferably, the difference between the minimum impedance index and the current impedance index is maintained for at least 4 minutes, more preferably for at least 6 minutes. The exact duration of the peak will depend on a number of factors in the process, particularly flow rates. When there is a small reservoir of resin 16, which is the amount of ion exchange resin 16 remaining downstream of the sensor probe 56, due to the size of the conditioner 10 or the placement of the probes 54, 56, the service step is ends immediately advantageously. Optionally, the termination of the service step is delayed according to any of a number of criteria. When the water that is currently used at the time when the controller 20 determines that the service step must be terminated, the regeneration is optionally delayed at least until the use of the water has been completed or minimized. If the resin reserve 16 is large enough, the regeneration may be delayed until a predetermined time of the day. As the ion exchange front passes through the preferred probe 54, the impedance index decreases to about one, since both probes 54, 56 will again be in water and resin 16 of the same condition.

At the appropriate time, the controller 20 terminates the service step and initiates the brine / slow regeneration rinse step. The imbalances between the impedance proportions of the probes 54, 56 are used to determine the duration of the regeneration step slightly differently than that used in the service step. More specifically, the ratio of the impedance between the two probes 54, 56 is determined and the rate of change in the impedance indices over a period of time is calculated. When the two specific peaks in the ratio of change in impedance indices are detected, the controller 50 terminates the brine / slow rinse step.

At the beginning of the brine / slow rinse cycle, both sensor 56 and reference 54 probes are in hard water and spent resin 16, which gives impedance indices that are constant and approximately equal. As the brine passes through the sensor probe 56, the reference sensor 54 is still in hard water. At this time, the sensor probe 56 will have a lower resistance than the reference probe 54 due to the relative conductivities of the different solutions. The impedance index is decreased until the brine interface passes through the reference probe 54 when the impedances will again be equal, which gives a constant impedance index. This rapid change in impedance index while sensor probe 56 is in brine and the reference probe is in hard water produces a marked first minimum peak when the rate of change in impedance indices is checked for a time. As in the service step, the impedance index is calculated based on voltage signals from the sensor probe 54 and the reference probe 56 detected by the microprocessor 50. When the difference in the impedance peaks exceeds a first rate of Default change for a predetermined time (preferably 32 seconds), the first peak has been detected.

While both probes 54, 56 are in brine during regeneration, the index remains approximately constant and the rate of change is almost zero. After the brine is exhausted and rinse water is introduced into the bed 14, a condition occurs when the sensor probe 56 is in rinse water and the reference probe 54 is still in brine. Rinsing water is often hard water, however, soft water is optionally used from another resin tank. At this time, the sensor probe 56 has a higher resistance than the reference probe 54, which results in a rapid change in the dance index. This rapid change in the dance index produces a pronounced second peak when the change in the dance index is followed over time. Measuring the index of change in the dance index over time allows the microprocessor to detect the maximum peak of dance index when the sensor probe 56 is in soft water and regenerated resin and the reference probe 54 is in spent brine. When both probes 54, 56 are at the same time in soft water and soft resin, the index again becomes approximately constant.

The peaks in the index of change in the dance index at the beginning and end of the brine passage through the bed 14 are easily recognizable and are useful for monitoring the brine / slow rinse step. Any of the peaks is detected when the rate of change in the dance index exceeds a predetermined rate of change. The default rate of change is any value that indicates that the difference between the current dance index and the previous dance index for that cycle approaches the maximum. The exact values are determined by characteristics of the probes 54, 56 and the tolerance to the premature termination of the regeneration. Increases in the rate of change in the dance index from approximately 0.5% to approximately 2.5% are especially useful when using the preferred AQUASENSOR probe. When the brine begins to pass through the bed 14, the first predetermined rate of change of preference is greater than 2%. Then, as the brine is exhausted and the second maximum passes through the bed 14, the second predetermined rate of change preferably is greater than 2%.

Preferably, both the second predetermined time and the third predetermined time are at least 30 seconds. The second predetermined time and the third predetermined time may be the same or their values may be different from each other. If the preferred time interval of 30 seconds is used, peak detection is guaranteed if it has a minimum duration that is at least as long as the time interval. More preferably, both the first and the second peaks are maintained for at least 12 seconds, and more preferably one minute or more.

The duration of any of these process steps depends on a number of factors. The size of the conditioner 10 and the depth of the resin bed 14 determine the maximum vertical separation between the reference probe 54 and the sensor probe 56. This separation and the flow velocities of the fluid determine at least partially how long it takes for a front to move the distance between the sensors 54, 56. The capacity for the ion exchange of the resin 16 determines at least in part how much salt 34 is needed to regenerate and how long the washing with brine lasts.

Optionally, the microprocessor 50 is configured to include a time out function that determines the brine / slow rinse step and initiates a warning if the first peak or the second peak is not within a reasonable period of time. The time period for the weather warning should exceed the time in which the peaks are expected to pass. A preferred time is slightly longer than the total expected time for the entire regeneration process. Optionally, the warning is an audible alarm or a visual alarm that is shown on the screen 64.

In a preferred exemplary illustrated in Figures 3 through 5, the microprocessor 50 in the controller 20 is programmed to perform a series of steps to carry out the preferred process. During the service step illustrated in Figure 3, at 100 the controller 20 measures the voltage of the reference probe, the sensor probe and the supply line at thirty-seven second intervals. These voltage signals are preferably analog type signal measurements. Preferably there is provided a digital-to-digital signal converter 102 or a microprocessor 50 with a built-in analog to digital converter, such as those manufactured by Hitachi (Tokyo, Japan), NEC (Princeton, New Jersey) and Toshiba (Irvine, California) in the controller 20 to convert the signals analogous to digital voltage signals to 104.

The impedance values for the reference probe 54 and the sensor probe 56 are calculated at 106 using the voltage values and known values of the reference resistors Ri, R2 on the Wheatstone bridge 62 using equations IX and X. The index of impedance of the two sensors 54, 56 is also calculated at 106 using equation XI. If this is the first data point in the service step, the current impedance index is recorded at 108 as the minimum impedance index and the controller waits for the next reading in thirty-seven seconds.

For subsequent readings in the service step, the current impedance index is recorded at 110, then compares at 112 with the minimum impedance index. If the current impedance index is lower than the minimum impedance index, the minimum impedance index is reset to 114 at the current value. The percentage change in the impedance index is calculated at 116 and compared to the predetermined increment and if it does not exceed 7.5%, a condition timer 118 is allowed at 120 and the controller 20 again waits for the next time interval. When the change in the impedance index exceeds 7.5%, the condition timer 118 starts at 122. If the change in impedance index falls below 7.5% in the next 6 minutes, the peak is considered erroneous and the regeneration is not start. Percentages and time intervals may vary to meet the application.

However, with reference to step 124, if the change in the impedance index lasts at least 6 minutes, then the controller 20 takes the steps necessary to initiate the regeneration 126 at an appropriate time. Regeneration can start immediately or can be delayed according to appropriate criteria. At this time, the controller stops at 128 initiating voltage readings from the reference probe 54, the sensor probe 56 and the power supply line every thirty-seven seconds.

Once regeneration has started as illustrated in Figure 4, a different program is started to determine the duration of the brine / slow rinse step. After one minute in the brine / slow rinse cycle, the controller 20 begins to measure 130 the voltage of the reference probe 54, the sensor probe 56 and the supply line (not illustrated). The analog signals are converted to 132 in digital signals using the same converter 102 as described in the service step above. The calculations are carried out at 136 to obtain the impedance of each probe and the impedance index. If this is the first data point in the current regeneration step, a value for the current impedance index is assigned at 138 to a previous impedance index, then the controller 20 waits for the next thirty-seven seconds interval to obtain new ones. values.

For the subsequent data points in the current regeneration step, the current impedance index is recorded at 140 and the percent change index in the impedance index is calculated at 142 as the difference between the current impedance index and the index of previous impedance divided by the previous impedance index. If in step 144 the rate of change increases by less than 2%, no peak is detected, the controller 20 starts a step timer in step 146 and the controller searches for the next thirty-seven seconds interval. If the increase in the rate of change in the impedance index exceeds more than about 2% in a 30-second interval and is maintained for at least 30 seconds, the first peak has been detected.

After detection of the first peak, a wait time may be inserted at 152 during which the control does not need to register signals during the time when peaks are not expected. For example, the waiting time can last from five minutes to 30 minutes, preferably at least 15 minutes. These times vary, for example, depending on the water flow rate and the placement of the reference probe 54 and the sensor probe 56 in relation to each other, and the salt dose.

With reference to Figure 5, after the detection of the first peak the controller continues measuring at 130 the voltage of the sensor probe 56, the reference probe 54 and the supply line, as well as the conversion to 132 of the analog values to digital, calculating in 136 the impedances and the impedance index, evaluating in 138 the first index of impedance as the previous index of impedance, registering in 140 the current index of impedance and calculating in 142 the percentage change in the index of Impedance as for the first previous peak.

If the rate of change in the impedance index does not meet the minimum rate of change, the second peak has not been recognized at 156 and the controller 20 resets the condition timer 118 and waits for the next measurement in thirty-seven seconds at 130 The second peak is recognized at 158 when the rate of change of the impedance index is determined at 154 greater than 2% and the condition is maintained at 160 for more than 30 seconds at the condition timer 118. After recognition of the second peak, the controller programs at 162 the termination of the regeneration step, either immediately or with a delay by the regenerator dose, time of day or other event.

Although the Wheatstone bridge 62 (Figure 2) monitors the voltage constantly, it is recorded in time intervals for use in calculations. The useful time interval for determining the rate of change in the impedance index is less than the duration of the peaks it seeks to detect, preferably between 10 and 60 seconds and more preferably between 20 and 40 seconds. Preferably the time intervals are regularly spaced.

While a particular instance of the present method for determining the duration of steps in a regeneration sequence has been illustrated and described herein, those skilled in the art will appreciate that changes and modifications can be made thereto without departing from the invention. in its broader aspects and as established in the following claims.

Claims (20)

1. A method for determining the duration of the service steps and brine / slow rinse in a process cycle for a water conditioner having a bed of material for ion exchange, comprising: placing a sensor probe and a reference probe in the bed of the material for ion exchange vertically separated from each other, with the sensor probe upstream of the reference probe; monitoring the voltage of each of the sensor probe and the reference probe during a plurality of time intervals; calculate the percentage change in the impedance index for the current time interval over the minimum impedance index of the service step; detecting an increase in the change in impedance index if the percentage change in the impedance index exceeds a first predetermined increment for a first minimum period of time; terminate the service based on said detection step; start a brine / slow rinse step; monitoring the voltage of each of the sensor probe and the reference probe during a plurality of time intervals; calculating the percentage rate of change in the impedance index for the current time interval with the impedance index of a previous time interval; detecting a first peak in the index of change in impedance index if the percentage rate of change in the impedance index exceeds a first predetermined change in the index for a first predetermined second time; monitoring the voltage of each of the sensor probe and the reference probe during a plurality of time intervals; calculating the percentage rate of change in the impedance index for the current time interval with the impedance index of a previous time interval; detecting a second peak in the rate of change in impedance index if the percentage rate of change in the impedance index exceeds a second predetermined change in the index for at least a predetermined third time; and finishing the brine / slow rinse step based on said third detection step;

2. A method for determining the duration of the brine / slow rinse step in a process cycle for a water conditioner having a bed of material for ion exchange, comprising: placing a sensor probe and a reference probe in the bed of the material for ion exchange vertically separated from each other, with the sensor probe upstream of the reference probe; monitoring the voltage of each of the sensor probe and the reference probe during a plurality of time intervals; calculate a rate of change in the impedance index of the sensor probe compared to the reference probe; detecting a first peak in the rate of change between the time intervals of impedance indices of the sensor probe compared to the reference probe; repeat said monitoring, calculation and detection steps until a second peak is detected; and finish the brine / slow rinse step after both peaks have been detected.

3. The method of Claim 2 wherein said first detection step comprises identifying an index of change in impedance indices of at least 2% in 30 seconds.

4. The method of Claim 2 wherein said second detection step comprises identifying a rate of change in impedance indices of at least 2% in 30 seconds.

5. The method of Claim 2 further comprising introducing a waiting time between said detection of the first peak and the start of monitoring for the second peak.

6. The method of Claim 5 wherein said waiting time is at least 15 minutes.

7. The method of Claim 2 further comprising delaying the completion of the slow rinse step after detecting the second peak.

8. The method of Claim 7 further comprising initiating a subsequent program step if the second peak is not detected within the out time slot.

9. The method of Claim 2 wherein the reference probe and the sensing probe of the monitoring step are variable resistances.

10. The method of Claim 2 wherein said monitoring and calculation steps are carried out with the aid of a microprocessor.

11. The method of Claim 2 wherein said monitoring and calculation steps are carried out with the help of a bridge circuit.

12. A water conditioner (10) having a controller (20) and a bed (14) of material for ion exchange (16), comprising: a sensor probe (56) placed in the bed (14); a reference probe (54) placed in the bed (14) downstream of said sensor probe (56); a circuit for monitoring the voltage of each of said sensor probe and said reference probe during a plurality of time intervals; and a controller (20) configured to monitor the voltages of said sensor probe (56) and said reference probe (54), calculate the impedance index of said sensor probe with said reference probe and complete at least one of the steps of service and the step of brine / slow rinse based on the changes in said impedance index, where if in the service step, the regeneration is programmed when the difference between the current impedance index and the minimum impedance index exceeds a predetermined difference and, if in the regeneration step, the programming of the termination of the regeneration if the rate of change of the impedance index exceeds a first change in predetermined index and after a waiting time the rate of change of the index of Impedance exceeds a second predetermined index change.

13. The water conditioner of claim 12 wherein said sensor probe (56) and said reference probe (54) each comprise a pair of variable resistors.

14. The water conditioner of Claim 12 wherein said controller (20) comprises a microprocessor (50).

15. The water conditioner of Claim 12 wherein said circuit includes a Wheatstone bridge circuit (62).

16. The water conditioner of Claim 12 wherein said controller (20) is further configured to allow a delay between detecting said second peak and ending the brine / slow rinse step.

17. A method for determining the duration of the service step in a process cycle for a water conditioner having a bed of material for ion exchange, comprising: placing a sensor probe and a reference probe in the bed of the material for ion exchange vertically separated from each other, with the sensor probe upstream of the reference probe; monitor the voltage of each of the sensor probe, the reference probe during a plurality of time intervals; calculating the percentage change in the impedance index for the current time interval compared to the minimum impedance index of the service step; detect a first peak in the change in impedance index if the percentage change in the impedance index exceeds 7.5% for at least six minutes; and terminate the service based on said detection step.

18. The method of Claim 17 wherein said monitoring step is carried out approximately every thirty-seven seconds.

19. The method of Claim 17 wherein said termination step further comprises scheduling a delay before the termination of said service step.

20. The method of Claim 17 wherein each of the sensor probe and the reference probe comprises a pair of variable resistors.