Electricity: measuring and testing – Electrolyte properties – Using a conductivity determining device
Reexamination Certificate
1997-10-22
2001-04-24
Do, Diep (Department: 2858)
Electricity: measuring and testing
Electrolyte properties
Using a conductivity determining device
C324S438000, C324S441000, C204S194000
Reexamination Certificate
active
06222371
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to portable, hand-held fluid testers for measuring the properties of a test fluid in the field. More particularly, it relates to a new and improved portable, hand-held fluid tester having improved sealing and assembly, electrical connection and fluid volume control features.
Hand-held fluid testers are currently available for measuring electrical conductivity of a process fluid such as boiler fluids or coolant fluids. These fluid testers include a fluid reservoir which contains electrodes to measure the electrical conductivity of the fluid in the reservoir. The electrodes are connected to a circuit board via jumper wires. Some models also include a thermistor to provide temperature compensation for more accurate measurement. If employed, the thermistor is typically mounted in a hole adjacent the fluid reservoir with a thin wall separation which sometimes breaks into the reservoir. These thermistors are usually connected to the printed circuit board via jumper wires. In some models, the thermistor is potted into place with a potting compound to both assemble the thermistor to the fluid reservoir and to insure sealing of any thin wall imperfections. With these conventional hand-held fluid testers, testing is performed by filling the fluid reservoir to a marked volume. This is typically done by line of sight and therefore the volume of test fluid introduced to the fluid reservoir may not be the same for all tests and may vary depending on the person doing the testing.
These conventional hand-held fluid testers have a number of important shortcomings. For example, the assembly of the electrodes and the thermistor to the reservoir wall is cumbersome and frequently requires the use of additional potting compounds or adhesives which are difficult to handle. The electrical connections between these devices and a testing circuit on a printed circuit board are typically provided via jumper wire leads which also must be individually handled and connected which increases labor associated with the assembly. Moreover, these devices do not provide any inherent test fluid volume controls so that wide variations in test results of and a lack of any meaningful calibration leads to unreliable results.
SUMMARY OF THE INVENTION
To overcome these and other shortcomings of the prior art devices, the present nvention provides a new and improved portable, hand-held fluid tester. In an embodiment, the portable, hand-held fluid tester comprises a tester body configured to be held in the hand including an upper surface and an opposed bottom surface. A first recess extends inwardly from the upper surface to a first end wall and defines a fluid reservoir for receiving a test fluid to be tested. A second recess extends inwardly from the upper surface to a second end wall to define an overflow reservoir which is disposed adjacent to the fluid reservoir. An angled spillway surface extends between and interconnects an upper end of the fluid reservoir to an upper end of the overflow reservoir.
A third recess extends inwardly from the bottom surface to a third end wall to define a test circuit receiving recess. At least one test probe member extends from the third wall into the first end wall and fluid reservoir and is sealingly engaged in the tester body. A test circuit in the test circuit receiving recess is operably connected with said at least one probe member for measuring at least one parameter of the test fluid introduced in the test fluid reservoir and reporting a result for the at least one parameter measurement. The fluid tester additionally includes a cover member releasably secured to the tester body closing off an opening of the third recess.
A major advantage provided by the new and improved hand-held fluid tester of the present invention is that the fluid tester is designed to provide repeatable test results by providing constant volume of fluid being tested. This feature is provided, inter alia, by the addition of a spillway to the wall of the test reservoir. The angled spillway surface is configured to overflow excess test fluid introduced in the fluid reservoir from the fluid reservoir to the overflow reservoir, thereby defining a maximum fluid volume for the fluid reservoir. Once the fluid level reaches the spillway, excess fluid is automatically drained off to insure a constant volume for the test fluid from test to test and from user to user leading to more consistent and accurate testing results.
In an embodiment, the portable, hand-held tester is provided for measuring electrical conductivity of a process fluid and in accordance with this embodiment, the at least one test probe member comprises a pair of cylindrical metallic electrodes each having a front end and an opposed rear end. The electrodes are mounted in the tester housing so that they extend into the third end wall with the front end of each electrode flush mounted in the first end wall of the fluid reservoir. Each electrode includes an external o-ring groove and an o-ring disposed in the groove by means of which each electrode is sealingly mounted in the tester housing.
In a preferred embodiment, the rear end of each electrode includes a threaded recess and the test circuit comprises a printed circuit substrate mounted in the test circuit receiving cavity. A pair of threaded mounting screws extend through the printed circuit substrate and each is respectively threadingly engaged in a threaded recess of an electrode to thereby electrically and mechanically connect the electrode with the test circuit. In accordance with this embodiment, lead wires are not necessary and a direct leadless connection is made between the electrodes and the test circuit substrate. This feature provides a more reliable assembly and electrical connection of the probes to the circuit board. This advantage is accomplished by providing a direct circuit board mounting of the probes.
In an embodiment, the portable, hand-held fluid tester further comprises a temperature probe. The temperature probe comprises a hollow cylindrical metal housing having a closed front end and an opposed open rear end with an elongate cylindrical thermistor receiving recess defined therein. A thermally conductive grease may be disposed in the thermistor receiving recess adjacent the closed front end. A thermistor operably connected with the test circuit is disposed in the thermistor receiving recess adjacent the closed front end in contact with the thermally conductive grease. The temperature probe extends into the third end wall of the tester housing with its closed front end extending into the first end wall and fluid reservoir. The temperature probe is sealingly mounted in the tester housing.
In a preferred embodiment, the sealed mounting of the temperature probe in the tester housing is provided by an external o-ring groove on the cylindrical metal housing and an o-ring disposed in said groove which is compressingly, sealingly engaged with the tester housing.
In accordance with this aspect of the invention, major advantages are provided because the arrangement provides faster and more reliable temperature compensation with improved sealing and assembly. This feature is accomplished by placing the thermistor in a thermal well of metallic material, more suited for heat transfer than standard potting compounds. The thermal well is inserted and sealed as a separate item and is therefore easily replaced and assembled with respect to the circuit board and housing.
Other objects and advantages provided by the present invention will become apparent from the following detailed description taken in conjunction with the drawings in which:
REFERENCES:
patent: 4303887 (1981-12-01), Hill et al.
patent: 4994397 (1991-02-01), Pagel
patent: 5269891 (1993-12-01), Colin
patent: 5644239 (1997-07-01), Huang et al.
patent: 5747666 (1998-05-01), Willis
patent: 5821399 (1998-10-01), Zelin
Do Diep
Hill & Simpson
Pulsafeeder Inc.
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