All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
This disclosure is generally related to dialysis machines and therapy. This disclosure is more specifically related to conductivity sensors in dialysis machines.
Some patients receive dialysis treatment at a dialysis center, which can place a demanding, restrictive and tiring schedule on a patient. Patients who receive in-center dialysis may have to travel to the dialysis center at least three times a week and sit in a chair for 3 to 4 hours each time while toxins and excess fluids are filtered from their blood. After the treatment, the patient may be required to wait for the needle site to stop bleeding and blood pressure to return to normal, which can require even more time taken away from other activities in their daily lives. In contrast to dialysis center treatments, home dialysis can provide patients with scheduling flexibility as it permits patients to choose treatment times.
A conductivity sensor is provided, comprising a first pair of sense electrodes having a first cell constant, a second pair of sense electrodes having a second cell constant different than the first cell constant, wherein the first and second pairs of sense electrodes are each configured to measure a conductivity of a fluid, and wherein the first and second pairs of sense electrodes combine to increase a range of conductivity measurements that fall below an acceptable error threshold.
In some embodiments, the conductivity is disposed within a dialysis system.
In one embodiment, the first cell constant ranges from 0.1 to 1.0. In another embodiment, the second cell constant ranges from 1.0 to 5.0.
In other embodiments, the first pair of sense electrodes comprises a first sense electrode and a second sense electrode. In another embodiment, the second pair of sense electrodes comprises a third sense electrode and a fourth sense electrode.
In some embodiments, the first and second sense electrodes are positioned between a first drive electrode and a second drive electrode. In other embodiments, the third and fourth sense electrodes are positioned between the second drive electrode and a third drive electrode.
In one embodiment, the conductivity sensor further comprises a first amplifier configured to measure voltages produced by the first and second pairs of sense electrodes. In another embodiment, the conductivity sensor further comprises a second amplifier configured to combine the measured voltages from the first amplifier. In yet another embodiment, the conductivity sensor further comprises an attenuation element configured to achieve scaled current subtraction with the second amplifier.
A method of measuring a conductivity of a fluid is provided, comprising the steps of measuring a first voltage of the fluid with a first pair of sense electrodes having a first cell constant, measuring a second voltage of the fluid with a second pair of sense electrodes having a second cell constant different than the first cell constant, processing the first and second voltages to produce first and second conductivity readings, and combining the first and second voltages to produce a combined conductivity reading that falls below an acceptable error threshold.
In some embodiments, the processing step further comprises processing the first and second voltages with a first amplifier to produce the first and second conductivity readings.
In another embodiment, the combining step further comprises combining the first and second voltages with a second amplifier to produce the combined conductivity reading that falls below the acceptable error threshold.
In one embodiment, the first cell constant ranges from 0.1 to 1.0. In another embodiment, the second cell constant ranges from 1.0 to 5.0.
A dialysis system is provided, comprising a water purification system configured to purify a water source for use with dialysis treatment, a dialysis delivery system configured to produce a dialysate from water purified by the water purification system, and further configured to provide dialysis treatment to a patient, and a conductivity sensor disposed in at least one of the water purification system and the dialysis delivery system, the conductivity sensor comprising a first pair of sense electrodes having a first cell constant, and a second pair of sense electrodes having a second cell constant different than the first cell constant, wherein the first and second pairs of sense electrodes are each configured to measure a conductivity of a fluid, and wherein the first and second pairs of sense electrodes combine to increase a range of conductivity measurements that fall below an acceptable error threshold.
In one embodiment, the first cell constant ranges from 0.1 to 1.0. In another embodiment, the second cell constant ranges from 1.0 to 5.0.
The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
This disclosure describes a novel approach for investigating neuronal signaling. The approach described herein exploits high dielectric permittivity of biological tissue to tunnel energy to the implantable devices in animals, that is, it uses tissue to facilitate the coupling of energy from the transmitter to the implanted receiver. Wherever the animal is located, energy can be tunneled automatically to the implanted receiver.
This disclosure describes systems, devices and methods related to embodiments of a dialysis system, including a home dialysis system, having a conductivity sensor or sensing system that measures conductivity in fluid associated with the dialysis system. For example, the conductivity sensor of the dialysis system can measure the conductivity of dialysate in order to determine its composition and verify proportioning of the dialysate. The conductivity sensor can also measure the purity of water and verify its proportioning in the dialysis system. In addition, the conductivity sensor can be configured to detect conductivity of the fluid within an acceptable range, as will be described in greater detail below.
The conductivity sensor can include drive electrodes (i.e., drives current) and sense electrodes (i.e., measures voltage). The drive electrodes can be powered by an alternating voltage, and current that flows from the drive electrodes through the fluid can be measured by the sense electrodes to determine the conductivity of the fluid. The conductivity of the fluid can be affected by one or more characteristics of the fluid, such as chemical composition and temperature.
For example, the conductivity sensor can drive a current through the fluid and measure a drop in voltage across the fluid. Based on the current, voltage, distance between sense electrodes and effective area between the sense electrodes, the conductivity sensor can calculate the conductivity across the fluid.
A number of variables in the dialysis system can interfere with conductivity measurements such that a more advanced conductivity sensor is needed. For example, electrical noise from other parts of the dialysis system and leakage currents can interfere with measuring conductivity of fluids within the dialysis system.
As shown in
As described above, a cell constant is the ratio of the distance between electrodes to the electrode area. The conductivity sensor 400 can have distinct cell constants between the pairs of sense electrodes as follows: For example, a first distance (d1) between the first and second sense electrodes 440a and 440b can be different than a second distance (d2) between the third and fourth sense electrodes 440c and 440d. Alternatively or in addition, a first area (A1) of the first and second sense electrodes 440a and 440b can be different than a second area (A2) of the third and fourth sense electrodes 440c and 440d. This can result in the cell constant created by the first and second sense electrodes 440a and 440b to be different than the cell constant created by the third and fourth sense electrodes 440c and 440d. The conductivity sensor 400 includes two pairs of electrodes with different cell constants, whereby the combination of these two different cell constants allows the conductivity sensor 400 to measure a wider range of conductivity measurements that are below an acceptable error threshold, as will be explained in greater detail below.
The embodiment illustrated in
Cell constants in conductivity sensor 400 can be tuned by either changing the distance or effective area between the pairs of sense electrodes in order to adjust the acceptable conductivity measurement range of the conductivity sensor 400. This can allow the conductivity sensor 400 to collect a broad range of conductivity measurements that are appropriate for the type of fluid being measured, along with the measurements being below the acceptable error threshold 524.
In some embodiments, additional electronics (e.g., sensors) can be included in the conductivity sensor 600 in order to ensure proper functioning. For example, conductivity sensor 600 can include a sensor 670 for measuring current along a section of the electrical pathway in order to ensure that the current is staying within a preferred range. The preferred range can be a single preset value or a dynamically tuned value that assists the conductivity sensor 600 with achieving precise conductivity calculations (i.e., minimize individual and combined measurement errors for voltage and current).
In addition, by independently measuring voltage across the pairs of sense electrodes, the conductivity sensor 600 can allow the sense electrodes to be placed in a variety of positions relative to each other between corresponding drive electrodes. Additionally, increasing the difference in cell constants in the conductivity sensor 600 can increase the acceptable range. The noise level can be decreased by decreasing the difference in cell constants.
A target conductivity range of water and dialysate, for example, can be from approximately 0 uS/cm to 1,000 uS/cm and approximately 8,000 uS/cm to 20,000 uS/cm, respectively. In addition, target cell constants for each pair of sense electrodes can be approximately 0.1 to 1.0 and approximately 1.0 to 5.0.
While this specification contains many specifics, these should not be construed as limitations on the scope of an invention that is claimed or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Only a few examples and implementations are disclosed. Variations, modifications and enhancements to the described examples and implementations and other implementations may be made based on what is disclosed.
As for additional details pertinent to the present invention, materials and manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts commonly or logically employed. Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Likewise, reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “and,” “said,” and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The breadth of the present invention is not to be limited by the subject specification, but rather only by the plain meaning of the claim terms employed.
This application claims the benefit of U.S. Provisional Appin. No. 62/052,410, filed Sep. 18, 2014, titled “Dialysis Machine Having a Conductivity Sensor for Determining Fluid Properties”, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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62052410 | Sep 2014 | US |