Patent Application
20150082879
The present disclosure relates to an improved fluid flow sensor and a method associated with quickly determining whether the sensor has been installed in an improper orientation relative to the direction of fluid flowing through a system.
This section provides background information related to the present disclosure and is not necessarily prior art.
The use of fluid flow sensors in household and industrial fluid delivery and/or fluid monitoring systems is common. For example, a fluid flow sensor may be installed in a household dishwasher to monitor and help control the volume of water flowing into the dishwasher to circumvent a potential under-fill or over-fill condition from occurring.
In a typical fluid system, generally, fluid flows through a supply hose in a single direction (i.e., either in a left to right direction, or in a right to left direction). A fluid flow sensor can generally connect to the supply hose in either orientation relative to the direction of fluid flowing through the hose. Accordingly, depending on the orientation that the sensor is connected to the hose dictates whether fluid will flow through the sensor in a left to right direction, or in a right to left direction. However, for the fluid flow sensor to function properly, the sensor must be installed correctly; that is, the sensor must be connected to the hose in proper orientation relative to the direction of fluid flowing through the hose. A sensor that has been installed in an improper orientation relative to the direction of fluid flow can, for example, fail to accurately monitor and control the volume of fluid passing through the system.
Improper orientation, or reverse-installation, can occur at the assembly facility where the sensor is first connected to the fluid system and/or in the field during sensor service or replacement. Unfortunately, there currently lacks a fluid flow sensor and a method associated with quickly determining whether the sensor has been installed in an improper orientation relative to the direction of fluid flowing through a system.
Fluid flow sensors and methods associated with detecting the presence of fluid in a fluid system and determining the rate of fluid flow through a system are generally known. For example, a sensor for realizing whether a threshold fluid level has been attained in a system is shown and described in U.S. Pat. No. 6,862,932, entitled “Liquid Level Sensor,” issued Mar. 8, 2005 and owned by Therm-O-Disc, Incorporated, the assignee of the present patent application, the disclosure of which is hereby incorporated by reference. A sensor for realizing the rate of fluid flow through a system is shown and described in U.S. Pat. No. 7,333,899, entitled “Fluid Flow Rate Sensor and Method of Operation,” issued Feb. 19, 2008 and in U.S. Pat. No. 7,685,875, entitled “Fluid Flow Rate Sensor and Method of Operation,” issued Mar. 30, 2010, both owned by Therm-O-Disc, Incorporated, the assignee of the present patent application, the disclosures of which are hereby incorporated by reference.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
A fluid flow sensor and a method associated with quickly determining whether the sensor has been installed in an improper orientation relative to the direction of fluid flowing through a system is disclosed.
In one form, the disclosure provides a fluid flow sensor comprising a probe with a detection module adapted to change condition in response to a direction of flow of fluid through a system. The detection module comprises a a first heating circuit having at least one resistor heater, a second heating circuit having at least one resistor heater, a fluid flow rate detection circuit, and a reverse-installation detection circuit having at least one negative temperature coefficient thermistor. The negative temperature coefficient thermistor of the reverse-installation detection circuit is adapted to provide a voltage that varies in response to a change in temperature.
The fluid flow sensor further comprises a control module electrically connected to the probe that monitors the condition of the detection module and generates an output that is indicative of the direction of flow of fluid. The fluid flow sensor also comprises an I/O module connected to the control module to communicate the output of the control module to another device or a user.
In another form, the present disclosure provides a fluid flow sensor comprising a detection module having a first heating circuit, a second heating circuit, a fluid flow rate detection circuit and a means for determining a direction of flow of fluid through a system.
In yet another form, the present disclosure provides a fluid flow sensor for detecting the direction of flow of fluid through a system comprising the steps of measuring a temperature of a fifth negative temperature coefficient thermistor, applying a voltage to a second resistor heater to generate heat that can be transferred to the fifth negative temperature coefficient thermistor, measuring a temperature of the fifth negative temperature coefficient thermistor, calculating a change in temperature of the fifth negative temperature coefficient thermistor, determining a direction of flow of fluid through the system from the change in temperature of the fifth negative temperature coefficient thermistor, and generating an output that is indicative of the direction of flow of fluid through the system.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. The example embodiments will now be described more fully with reference to the accompanying drawings.
The present disclosure provides a fluid flow sensor and method associated with quickly determining whether the sensor has been installed in an improper orientation relative to the direction of fluid flowing through a system. By way of example only, it is presently contemplated that the fluid flow sensor of the disclosure can be incorporated into a household dishwasher to monitor water flow therethrough.
The sensor 10 is of the thermo-anemometer-type and contains no moving parts. The probe 12 is typically disposed in a fluid environment 20. The sensor can be used to determine the flow rate of a fluid 18 and the direction of fluid flow 18. As described further herein, the sensor 10 can quickly determine whether the probe 12 is installed in an improper or reverse orientation relative to the direction of fluid flow 18.
When the probe 12 is subjected to fluid flow 18, the probe 12 experiences a change in condition represented by a signal 22 (e.g., a voltage). The control module 14 continuously monitors the signal 22. According to one aspect of the disclosure, the control module processes the signal 22 and generates an output 24 that is indicative of the installation orientation of the probe 12 relative to the direction of the flow of fluid 18 through the probe. In another aspect of the disclosure, the control module processes the signal 22 and generates an output 24 that is indicative of the flow rate for the fluid 18. The I/O module 16 provides a means by which the sensor 10 can communicate the output 24 to other devices(s) or a user.
An embodiment of a probe 100 for use in the sensor 10 is shown in
The probe 100 can generally connect to the supply hose in either orientation relative to the direction of fluid flowing through the hose. Accordingly, depending on the orientation that the probe 100 is connected to the hose dictates whether fluid will flow 18 through the passageway 106 in a left to right direction, or in a right to left direction. As discussed above, because the sensor 10 may not function properly when fluid flows 18 through the passageway 106 in one direction versus the other, it is desirable for the sensor 10 to quickly determine if the probe 100 has been installed in an improper or reverse orientation relative to the direction of fluid flow 18.
Located intermediate the annular flanges 108, 110 is a housing 116. The housing 116 extends through the body 102 in a direction generally perpendicular to the longitudinal axis 107, and is disposed within the passageway 106. The shape of the housing 116 is designed to promote laminar fluid flow 18 through the passageway 106 and across the surface of the housing 116. The detection module 104 is received within the housing 116 such that the housing 116 encapsulates a portion of the detection module 104 and protects it from physical contact with the fluid 18. The housing 116 is, however, capable of conducting thermal energy between the fluid 18 and the detection module 104.
Both the body 102 and the housing 116 are preferably manufactured from a thermally conductive polymer, such as, for example, polypropylene, polyvinyl chloride (PVC), polyacetylene, polyparaphenylene, polypyrrole, and polyaniline. Ceramic and/or glass fillers mixed in with these base polymers have been shown to greatly enhance the material's thermal conductivity. One such material is known under the trade designation Konduit MT-210-14 and is available from GE/LNP.
A representative detection module 104 can be understood with reference to
Referring to
The reverse-installation detection circuit 114 comprises a negative temperature coefficient (NTC) thermistor NTC5, which is arranged to operate as a temperature sensing thermistor.
The fluid flow rate detection circuit 115 comprises a plurality of negative temperature coefficient (NTC) thermistors NTC1, NTC2, NTC3, NTC4 that together form a 4-wire bridge circuit 132. Thermistor NTC1 is coupled in series with thermistor NTC3 to form one leg of the bridge 132 and thermistor NTC2 is coupled in series with thermistor NTC4 to form the other leg of the bridge 132. Together, thermistors NTC1, NTC3 are coupled in parallel with thermistors NTC2, NTC4.
The circuit schematic 122 of
The second heating circuit 113 includes traces 127, 128 and pins P4, P5. Trace 127 terminates at pin P4, where a voltage VHR2 is applied to turn ON and energize resistor heater R2. As described above, trace 128 terminates at pin P5, which is connected to ground.
The reverse-installation detection circuit 114 includes traces 124, 125 and pins P1, P2. An output voltage VOUT2, which is calibrated to represent a temperature of thermistor NTC5 can be read at pins P1, P2.
The fluid flow rate detection circuit 115 includes traces 124, 126, 129, 131 and pins P1, P3, P6, P8. Trace 124 terminates at pin P1, which is connected to ground. Trace 129 terminates at pin P6, where a reference voltage VREF1 is applied. Traces 126, 131 are coupled to opposite legs of the bridge 132 and terminate at pins P3, P8, respectively. An output voltage VOUT1, which is calibrated to represent a temperature difference across the bridge 132 and between thermistors NTC1, NTC3 and NTC2, NTC4, can be read at pins P3, P8.
Thermistors NTC1, NTC2, NTC3, NTC4 are generally disposed on side A of the substrate 120. Thermistors NTC1, NTC2 are located generally proximate a first, downstream edge 136 of the substrate 120. Thermistors NTC3, NTC4 are located generally proximate a second, upstream edge 138 of the substrate 120, opposite the first edge 136. Thermistors NTC1, NTC3 are generally located above thermistors NTC2, NTC4.
Thermistor NTC5 and resistor heaters R1, R2 are generally disposed on side B of the substrate 120. It is understood, however, that resistor heater R2 can be relocated to side A of the substrate 120. As shown in
Resistor heater R2 is generally located between thermistor NTC5 and resistor heater R1, and can be positioned closer to the second edge 138 of the substrate 120, and relatively proximate to thermistor NTC5.
As discussed below, heat energy from resistor heater R1 is generally conducted to thermistors NTC1, NTC2. Heat energy from resistor heater R1 is generally not, however, conducted to thermistors NTC3, NTC4, NTC5.
Thermistors NTC3, NTC4, disposed on side A of the substrate 120, are positioned generally opposite thermistor NTC5 and near resistor heater R2, both of which are disposed on side B of the substrate 120. As will be described further below, heat energy from resistor heater R2 can be conducted to thermistor NTC5 depending on the direction of fluid flow 18 through the passageway 106 of the probe 100. Heat energy from resistor heater R2 is not, however, conducted to thermistors NTC1, NTC2, NTC3, NTC4.
The detection module 104 disposed on the PCB substrate 120 is generally received within the housing 116 such that it is generally perpendicular to the direction of fluid flow 18 through the passageway 106. With particular reference to
The sensor 10 of the present disclosure can generally operate in two modes: a fluid flow rate detection mode and a reverse installation detection mode. Of course, it will be appreciated by persons skilled in the art that the reverse installation detection mode can also serve to determine the direction of fluid flow.
First, the rate of fluid flow 18 through the probe 100 is determined. Preferably, a minimum threshold fluid flow rate through the probe 100 in the range of 1 to 5 liters per minute (LPM), should be present before the sensor 10 operates to detect the whether the probe 100 has been installed in a reverse orientation. If the rate of the fluid flow 18 through the probe 100 is below the minimum threshold fluid flow rate, the sensor's 10 ability to accurately determine whether the probe 100 has been properly installed relative to the direction F of flow of the fluid 18 can be compromised.
To determine the rate of fluid flow 18 through the environment 20, at 150, the control module 14 applies a voltage VHR1 to pin 7 to turn ON and energize resistor heater R1. As a result, the temperature (Ti) of thermistors NTC1, NTC2 increases. The temperature of thermistors NTC1, NTC2 is determined from the output voltage VOUT1, which is read at pins P3, P8 by the control module 14, as described and taught in U.S. Pat. No. 7,333,899, entitled “Fluid Flow Rate Sensor and Method of Operation,” issued Feb. 19, 2008, which is hereby incorporated by reference. The temperature of thermistors NTC3, NTC4, NTC5 is not, however, affected by turning ON and energizing resistor heater R1 at 150. The reference voltage VREF1 is applied to the fluid flow rate detection circuit 115.
As fluid flows 18 through the passageway 106, passes over and around the housing 116 and consequently flows over the portion of the detection module 104 enclosed within the housing 116, heat energy is transferred from thermistors NTC1, NTC2 to the fluid 18. Accordingly, the temperature (Ti) of thermistors NTC1, NTC2 changes over time (t). The temperature (Ti) of thermistors NTC1, NTC2 and the output voltage VOUT1 is sampled by the control module 14 at discrete time intervals (e.g., 100 msec).
The use of four thermistors NTC1, NTC2, NTC3, NTC4 in the fluid flow rate detection circuit 115 and their physical arrangement in the passageway 106 of the body 102 provides significant advantages. One significant advantage is that the output voltage VOUT1 automatically compensates for any ambient temperature changes, i.e., changes in the temperature of the fluid 18. This is important because if significant and/or rapid changes in the fluid 18 temperature occurs, the output 24 of the sensor 10 could be distorted, thereby causing the sensor 10 to generate inaccurate results, as described and taught in U.S. Pat. No. 7,333,899, entitled “Fluid Flow Rate Sensor and Method of Operation,” issued Feb. 19, 2008.
Once the control module 14 samples the output voltage VOUT1 at discrete time intervals (e.g., 100 msec), the control module 14 then determines the rate of change of the temperature (Ti) over time (t) (i.e., it calculates dTi/dt). This process is repeated for a predetermined number of iterations (e.g., 10). Then, the smallest value of dTi/dt can be correlated to a fluid flow rate. At 152, the control module compares the rate of fluid flow 18 to the minimum threshold fluid flow rate to determine whether to proceed to the next step.
As discussed above, if the rate of fluid flow 18 through the passageway 106 is below the minimum threshold fluid flow rate, the sensor's 10 ability to accurately detect the orientation of the probe 100 relative to the direction of fluid flow 18 can be diminished. Consequently, preferably, the process will not proceed until the rate of fluid flow 18 through the passageway 106 is at or above the minimum threshold fluid flow rate.
If the rate of fluid flowing 18 through the passageway 106 is above the minimum threshold fluid flow rate, at 154, resistor heater R1 is turned OFF and the process proceeds. At 156, the control module 14 reads VOUT2 at P1, P2 and records a temperature T0 of thermistor NTC5. At 158, the control module 14 then applies a voltage VHR2 to pin P4, to turn ON and energize resistor heater R2. As fluid 18 flows through the passageway 106 and passes over and around the housing 116 and consequently over the portion of the detection module 104 that is enclosed within the housing 116, heat energy is transferred from resistor heater R2 to the fluid 18. The fluid 18, therefore, heats as it passes the resistor heater R2 and its temperature rises accordingly.
Referring to
Conversely, with reference to
Referring back to
If a reverse installation condition is determined, resister R2 is turned OFF at 168, and the control module 14 generates an alarm at 170, which can be communicated by the I/O module 16 to other device(s) and/or a user (e.g., audibly and/or visually) to convey the reverse installation condition of the probe 100. The improper installation of the probe 100 can, therefore, be corrected.
If, however, the temperature difference ΔT at 164 is less than the predetermined threshold value, that indicates that the probe 100 is installed in a proper orientation relative to the direction F of fluid flow. Thereafter, the resistor heater R2 is turned OFF at 166. Once the sensor 10 confirms the proper installation orientation of the probe 100, the sensor 10 can then be used to determine a fluid flow rate.
As mentioned above, it can be appreciated that the reverse-installation detection operating mode of the sensor 10 can also be used to determine whether there has been a change in the direction of flow of fluid through the probe 100. In this regard, as described above, the sensor 10 of the disclosure can determine whether the probe 100 has been properly installed relative to a known or expected direction of fluid flow. If, however, after proper installation of the probe 100 accordingly, the sensor 10 can employ the foregoing method to determine whether the direction of fluid flow has changed (e.g., reversed).
It can be further understood that the sensor 10 described in the present disclosure may also be incorporated into a multi-function sensor such as the sensor shown and described in U.S. Pat. No. 7,775,105, entitled “Multi-Function Sensor,” issued Aug. 17, 2010 and owned by Therm-O-Disc, Incorporated, the assignee of the present patent application, the disclosure of which is hereby incorporated by reference.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
