Pressure sensor

Details Pressure sensor Pressure sensor

1998-02-20

2001-08-14

Fuller, Benjamin R. (Department: 2855)

Measuring and testing

Dynamometers

Responsive to force

Reexamination Certificate

active

06272936

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to pressure sensors and more particularly to flexible pressure sensor assemblies and to handles for use with such assemblies.
BACKGROUND OF THE INVENTION
There are many applications where a need exists to detect pressure between two contacting surfaces, either at a single point, or at a plurality of points so as to provide a pressure profile. Such applications include detecting pressure at gaskets, seals, and other contacting surfaces in various industrial equipment for alignment, adjustment, various other set-up functions, testing, maintenance, and the like; in research facilities for measurement and testing of various products; and in medical facilities for measuring and testing such things as foot pressure distribution, dental occlusion and the like. While pressure sensors for certain of these applications are fabricated as a matrix array, many of these applications require only one or more button sensors, the output or outputs from which are read locally, are fed to a computer, either directly or indirectly, or are otherwise utilized.
In order to achieve optimum sensitivity for a given application, it is desirable that the sensor utilized be selected so as to function optimally in the pressure range being measured. Thus, where the pressure range over which measurements are being taken is small, and detection of small pressure changes is desired, high sensitivity sensors are required; while where the pressure range extends over many pounds or kilograms, sensitivity at the ounce or gram level may be more than adequate. Further, while the sensor elements interposed between the contacting surfaces for which pressure is being measured are high wear items which may only be suitable for a single test or a small number of tests, the remainder of the equipment may have an extended lifetime. Therefore, it is desirable to design sensor equipment with low-cost, flexible pressure sensor assemblies having various configurations and sensitivities which can be easily inserted and removed from a handle which may be connected directly or indirectly to a computer receiving the measurements, or may otherwise output the measurements. While the handle is generally little more than a connector to the pressure sensor assembly, it may, in some applications, also contain selected circuitry. For example, since the output from the sensors may be at relatively low voltage and/or current, the handles for the sensor assembles may contain amplifiers for such signals. Further, since analog output signals are subject to distortion, such handles may also contain converters for changing analog outputs from the sensors to digital signals applied to the computer and for converting digital control signals from the computer to analog. For example, the computer may control the test voltage applied to the sensor(s) to control sensitivity.
One problem with such handles is assuring that the sensor is properly seated in the handle before measurements are taken, since improper seating of the sensor in the handle can result in either erroneous readings being taken or in a loss of data which may be difficult to subsequently reconstruct. Two factors contribute to and insure proper seating has occurred before measurements are taken. The first factor is to design the sensor and handle such that the sensor may be easily inserted and removed while still assuring that, when in use, sufficient pressure is applied against the sensor assembly to assure good electrical contact between its terminals and those of the handle. The second factor is to provide a simple way of detecting good electrical contact between sensor assembly and handle terminals and of providing feedback to the user or operator that good electrical contact has been established before a sensor assembly is used to take measurements. If the user does not obtain such feedback, measurements would not be taken and the sensor assembly could either be repositioned until it is properly seated, or disposed of if defective. While there are a number of sensor products of the general type indicated above currently on the market, none adequately combines ease of use with the protection factors indicated above against measurements being taken with an improperly seated sensor assembly.
SUMMARY OF THE INVENTION
In accordance with the above, this invention provides a pressure sensor assembly and a handle for use therewith, the two combining to form a novel pressure sensor mechanism. In its simplest form, the pressure sensor assembly includes a pair of substrate sections secured together adjacent each other to form the assembly. The substrate sections are preferably flexible. A pressure sensor formed of a pair of electrodes with pressure sensitive material therebetween is formed at the distal end of the assembly. Leads extend from each electrode, which leads are electrically isolated from each other, to a corresponding terminal at the proximal end of the assembly. The assembly is constructed such that electrical contact to all terminals can be made from the same side of the assembly. For preferred embodiments, the assembly also has a third electrode which is electrically connected to one of the other two electrodes by a lead which functions as a sensor-ok lead or trace.
More particularly, for preferred embodiments, the first and second substrate sections are formed on the same substrate which is folded at a point substantially midway between the two sections to bring the two sections adjacent each other. An electrode is formed at the distal end of each of the substrate sections and a layer of pressure sensitive material is provided between the electrodes, by example, by forming a layer of pressure sensitive material over at least one of the electrodes. A lead extends from the electrode on each substrate to a terminal on the substrate, with the leads being on opposite sides of the assembly when the substrates are secured adjacent each other. For a preferred embodiment, when sections are secured together, and in particular when pressure is applied thereto, the lead-terminating terminal on a second of said substrates makes electrical contact with a terminal on a first of the substrates which terminal is connected by a lead to one output terminal on the first substrate. The other output terminal terminates the lead at the same substrate. The two output terminals are thus accessible from the same side of the assembly. A cutaway or window is provided through the second substrate to permit electrical contact to be made with the terminals on the first substrate. A fourth terminal may be provided on the first substrate which is connected by a sensor-ok lead or trace to the lead-terminating output terminal on the first substrate, the sensor-ok trace being used in a manner to be described later to detect and assure good electrical contact between sensor assembly and handle terminals. While for a preferred embodiment only a single sensor is formed at the distal end of the assembly, a plurality of sensors may also be formed at such distal end.
A handle which is adapted for use with one of the pressure sensitive assemblies indicated above includes a circuit board having a pad or terminal corresponding to each terminal on the assembly to which contact can be made from the one side, a slot sized to permit the proximal end of the assembly to fit therein, which slot has guide surfaces to position each terminal of the assembly adjacent the corresponding terminal on the circuit board; a member normally applying pressure to the side of the assembly opposite that containing the exposed terminals when the proximal end of the assembly is in the slot so as to facilitate good electrical contact between the assembly terminals and the corresponding terminals on the board; and a mechanism for permitting the pressure to be released to facilitate insertion and removal of an assembly from the slot. For preferred embodiments, the member for normally applying pressure includes a pivot arm and a means for biasing the pivot arm against the circuit board; and the mechan

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