Abstract:
A method, device and system are provided for measuring multiple pressures under severe conditions. In one embodiment, a method comprises receiving, by a processor, from a first sensor, a first pressure signal; receiving, by the processor, from a second sensor, a second pressure signal; receiving, by the processor, from a first memory, a first correction coefficient for the first sensor; receiving, by the processor, from a second memory, a second correction coefficient for the second sensor; modifying, by the processor, the first pressure signal using the first correction coefficient to generate a first corrected pressure signal; modifying, by the processor, the second pressure signal using the second correction coefficient to generate a second corrected pressure signal; and outputting, by the processor, the first corrected pressure signal and the second corrected pressure signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 13/253,139, filed Oct. 5, 2011, which is a continuation application claiming priority to U.S. patent application Ser. No. 12/321,521, filed Jan. 22, 2009, now U.S. Pat. No. 8,061,213, issued Nov. 22, 2011, all of which are entitled “HIGH TEMPERATURE, HIGH BANDWIDTH PRESSURE ACQUISITION SYSTEM,” and all of which are incorporated by reference in their entirety as if fully set forth below. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to pressure transducer systems and more particularly to a system for measuring multiple pressures under severe conditions. 
     BACKGROUND OF THE INVENTION 
     There is a need in many applications for measuring a set of pressures or multiple pressures along a given surface. These measurements, for example, are made in a wind tunnel where sensors may be placed on the wing of an airplane at different locations. The wind tunnel subjects the model, such as the wing of an airplane or other model, to extreme temperatures, vibrations and high wind velocity. A common method, which is employed, is to use a pressure scanner. Such a scanner essentially is a small box with a number of pressure sensors inside. Tubes are run from the pressure surface to the scanner in order to measure the pressure. As one can ascertain, such a device is depicted in U.S. Pat. No. 3,930,412 issued on Jan. 6, 1976 to A. D. Kurtz, et al. and entitled “ELECTRICALLY SCANNED PRESSURE TRANSDUCER CONFIGURATIONS.” That patent which is assigned to Kulite Semiconductor Products, Inc., the assignee herein. There is shown a plurality of individual pressure transducers which are mounted or fabricated within a common housing. Each pressure transducer is associated with a separate and distinct pressure port and can be subjected to a different one of a plurality of pressure sensitive locations to be monitored. The pressure transducers are electrically scanned by means of a scanning device such as a shift register or counter so that their individual outputs can be recorded. If one makes reference to the above-noted patent, one will see that the discussion of wind tunnel measurements is given and various other publications which are pertinent to such a scanner are also depicted. 
     While the scanner has been utilized, the disadvantages are that the response rate of such a system is greatly lowered because of the fact that long tubes must be run from the scanner module to various points along the wing of an aircraft. As one can ascertain, the wing of an aircraft could be extremely long and therefore the pressure tubes that are directed from the pressure scanner are long and therefore is very difficult to get frequency data more than a few tens of hertz. In any event, as depicted from the above-noted patent, it has the advantage of being a compact system and does not require a great deal of cabling from the scanner to the outside computer system. 
     Another method of measuring the pressure along a surface is to place individual pressure sensors at each measurement point. The output of each of these sensors is then directed back to a central data acquisition system. This configuration has the advantage of allowing high frequency data to be taken but it makes the measurement much more complicated because the output from each pressure sensor must be digitally converted and electrical lines must be run from the sensor to a central data acquisition system. This also requires a great deal of time installing the system as well as retrieving the data from the system. In any event, based on the above, it is a object of the present invention to provide a pressure system for measuring a multiplicity of pressures as in a wind tunnel, each under extreme conditions of temperature and vibration and to enable the system to be simply implemented and maintained. 
     SUMMARY OF THE INVENTION 
     Apparatus for measuring a plurality of pressures, comprising: a plurality of sensor devices, each capable of providing an output voltage indicative of an applied pressure, with each output voltage having a unique error voltage due to undesirable variations with temperature and pressure, an electronic assembly including multiple inputs each for receiving an associated output sensor voltage via a single cable from said associated sensor to said associated electronic assembly input, a memory having a plurality of storage locations, with each location associated with an associated sensor device for storing therein compensation values indicative of said error voltage and associated with said associated sensor, and processing means located in said electronic assembly and responsive to said sensor output voltages and said stored components for providing outputs indicative of each sensor output voltage as compensated by said stored components. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a simple block diagram depicting the pressure acquisition system according to this invention 
         FIG. 2  is a block diagram depicting an embodiment of the present invention. 
         FIG. 3  is a block diagram depicting an alternate embodiment of the present invention. 
         FIG. 4  is a schematic depiction of a connector configuration employed with the present invention. 
         FIG. 5  is a schematic diagram of a pressure sensor bridge circuit used in this invention. 
         FIG. 6  is a block diagram of the Acquisition and Compensation electronics module employed with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is a depicted a simple block diagram of a pressure system according to the present invention. As seen in  FIG. 1 , individual transducers such as  10 ,  11 ,  12  and  15  are connected via electrical lines or cables to a central module  20 . The module  20  designated as an Acquisition and Compensation electronics  20 , and receives multiple inputs from the pressure sensors as  10 ,  11 ,  12  and  15 . The pressure sensors, each as indicated, are individual transducer assemblies and are positioned on various points along the model to be tested. As indicated above, this may be an aircraft wing or some other object which is placed in a wind tunnel. The Acquisition and Compensation electronics  20  digitally converts the data from the transducers and then compensates the data for various temperature effects. The data from each of the sensors, as  10 ,  11  and so on, can then be sent on a digital bus  21  to a central computer. An advantage of the present system, as will be further explained, is that because each individual sensor does not have any compensation they can be made very small and made to operate at high temperatures without any loss of accuracy. In this manner, a large number of sensors, as  10 - 15 , can be used in a small volume even under extreme environmental conditions. The electronics can be mounted in close vicinity but in a much safer environment. It is of course desirable to utilize a sensor which can be subjected to high vibration applications and such a sensor, for example is described in U.S. Pat. No. 5,955,771, issued on Sep. 21, 1999 to A. D. Kurtz et al. and assigned to the assignee herein. That patent depicts a hermetically sealed sensor device, which has a glass member defining a mounting surface and a base surface. The glass member includes one or more pin apertures extending through the glass member from the mounting surface to the base. A metallic pin is disposed in each of the pin apertures. The sensor device includes a semiconductor sensor chip, including a semiconductor device and a cover which is bonded and sealed to a surface of the semiconductor device to protect the device from the external environment. As indicated, the chip is hermetically bonded and sealed to the mounting surface of the glass member. The semiconductor device has one or more contacts disposed on the surface and for making electrical contact to the device. The portion of each pin extending above the mounting surface is received within the contact apertures and a conductive glass frit is disposed in the contact apertures. This structure provides a hermetically sealed sensor device, which is capable of high temperature operation and capable of withstanding high vibration modes. As indicated, the above-noted U.S. Pat. No. 5,955,771 is incorporated herein in its entirety and as indicated again, such a sensor can be used for sensors depicted as  10 ,  11 ,  12  and  15  of  FIG. 1 . 
     Referring to  FIG. 2 , there is shown a first embodiment of the present invention. In regard to  FIG. 2 , the transducers as  10 ,  11 ,  12  and  15  are permanently fixed to the electronic assembly  20 , so that each transducer is assigned a fixed channel number in the electronics. In this way the coefficients for digital correction are programmed into the electronics and stored there permanently. Both the pressure output and the temperature of the individual sensors are detected through the measurement of the common mode voltage and the differential output voltage. These measurements are well known and depicted in the prior art. The transducers or sensors such as  10 ,  11  and  12  can be attached via cables of whatever length may be suitable for the application. For example, sensor  15  is coupled via cable  17  to module  20 . To make the cabling neater and to avoid tangles, one can utilize a spring loaded reel device such as reel device  13 ,  16  and  18 . Such reel devices are well known and would allow for automatic retraction of the transducers when not in use. As seen, the reel devices associated with each transducer can be positioned in the housing  14  or can be positioned in the Acquisition and Compensation electronics module  20 . In any event, it is shown that reel  13  is positioned within housing  14  while reel  16  and  18  are shown outside. It is of course understood that any location of the various reels can be employed. Thus as seen in  FIG. 2 , each of the transducers is directly wired to the Acquisition and Compensation electronic module or housing  20 , which again, interfaces with a digital output bus  21  which again goes to a central computer or other location. 
     Referring to  FIG. 3 , it is shown that each transducer as  10 ,  11 ,  12  and  15  is connected to the Acquisition and Compensation electronics module  20  via a cable with a connector on the end. Thus transducer  15  is connected via a cable  31  to a connector module  26 . Transducer  40  is connected via cable  41  to a connector  30  which is associated with a mating connector receptacle  42 . As can be seen, each of the transducers as  10 ,  11 ,  12  has a connector at the end of the cable which is associated with a mating connector on the housing  20 . Thus sensor  12  has a cable  43  which is directed to a male or female connector  44 , which mates with a connector  45 , which connector  45  is mounted on the module  20 . In this manner, each of the sensors or transducers is connected to the main module  20  via an associated cable with a connector on the end. 
     Referring to  FIG. 4 , there is shown another way of combining a sensor or transducer with the electronic module  20 . This would allow for any transducer to be plugged into any channel. As seen in  FIG. 4 , a small memory chip  52  is added to the connector on each transducer. Thus as seen, the connector  51  has the memory chip  52  connected thereto, connector  51  has output pins such as  56  to  57 , while the cable  58  goes to the sensor which is the transducer  59 . The memory chip, for example, may be a small memory such as an EEPROM. The coefficients for correction are stored in the transducer. The digital electronics can then read these coefficients and use them for digital correction. This can be done by software which the user would program in the correct coefficients for each transducer after all the connections are made. Thus, the EEPROM or the memory  52  stores the coefficients associated with the sensor  59 . In this manner, when sensor  59  is plugged into a connector of the electronic module  20 , it automatically has all the coefficients stored in memory  52 . Thus, the connector  51  can be inserted into any matching connector on the electronic module assembly  20 . Thus as seen from  FIG. 4 , the sensor  59  can be inserted into connector  42 ,  29  or  45  of  FIG. 3  and the coefficients as stored in the memory  52  would always be available to the electronic module  20  and be definitive of transducer  59 . 
     Referring to  FIG. 5 , there is shown a simple sensor configuration. A typical sensor, which may be a full bridge includes four piezoresistors as  61 ,  62 ,  63  and  64 . The piezoresistors are semiconductor resistors which may be diffused or otherwise located on a thin silicon or other diaphragm. The diaphragm will flex upon application of a force thereto. In this manner, the piezoresistive devices are force or pressure sensitive and the resistances vary according to the force applied to the active area of the diaphragm. Such configurations are extremely well known. In any event, as seen in  FIG. 5 , the bridge configuration  60  depicted, will have various attributes or error values concerning temperature variation as well as variations in applied pressure over temperature ranges and so on. These coefficients involving temperature and pressure are stored in the EEPROM  52  for each of the sensors as sensor  59  and  60 . It is also understood that each sensor can have its coefficients separately stored in memory. The compensation of such sensors regarding the prior art is well known and the assignee has patents showing compensation of sensors for temperature and pressure. Reference is made to U.S. Pat. No. 4,192,005 entitled “COMPENSATED PRESSURE TRANSDUCER EMPLOYING DIGITAL PROCESSING TECHNIQUES,” issued on Mar. 4, 1980 to A. D. Kurtz and assigned to Kulite Semiconductor Products, Inc., the assignee herein. That patent is the first early showing of a semiconductor sensor configuration which employs piezoresistors in a bridge configuration. The patent depicts a memory, which has stored therein, predetermined values indicative of error voltages associated with the particular bridge circuit due to undesirable variations of temperature and pressure. The bridge circuit is coupled to digital processing circuitry which serves to access the memory at desired locations to retrieve the values stored and to process these values in order to compensate the output signal supplied by the bridge during operation. This provides a compensated output signal truly determinative of the applied pressure as being compensated for the particular error signals associated with the semiconductor sensor configuration and as stored in the memory. Thus, as one can ascertain, the same processing technique can be employed together with this invention where in one embodiment, for example, the error voltages associated with the particular bridge circuit due to variations of temperature and pressure are stored in the electronic module  20 . In another example, these error signals would be stored in the memory  52  associated with the connector  51  as depicted in  FIG. 4 . Thus, by being able to attach the sensors directly to the surface of the model, such as the wing of the aircraft and so on, it would be possible to take high accuracy measurements without sacrificing temperature or frequency response. The sensors can operate at temperatures in excess of a thousand degrees Fahrenheit, and the electronics can be located remotely and one can still receive the detailed information about the aerodynamics of the surfaces being tested as well as the apparatus being tested. 
     Referring to  FIG. 6 , there is shown a block diagram of the high temperature, high bandwidth pressure acquisition system according to this invention. As seen in  FIG. 6 , there is a plurality of sensors  70  to  71 . These sensors, for example, are piezoresistive Wheatstone bridge configurations as shown in  FIG. 5 . In any event, each of the sensors has an output connected to a multiplexer as  72 . The multiplexer  72  as is well known, can select the output of any sensor according to the multiplexing frequency. The multiplexer  72  can be controlled in operation by the microcontroller  75 . As seen in  FIG. 6 , the output of the multiplexer  72 , which is the sensor multiplexer can be coupled to an analog amplifier  73 . This analog amplifier  73  is optional and depends upon the voltage output levels of the sensor assemblies. In any event, the analog output obtained from the multiplexer indicative of the output of each of the sensors is now converted into a digital signal via an analog to digital converter  74 . One can use one analog to digital converter per channel or use it with the multiplexer  72  depending on the data rate needed. In any event, the output of the A-to-D converter provides pressure and temperature data regarding each sensor. This data is applied to an input bus of a microprocessor or microcontroller  75 , which has its own internal memory  76 . Also shown is a plurality of memories as  80  to  81 . Each memory, for example as memory  80  is associated with a sensor as  70  while memory  81  for example, is associated with sensor  71 . The memory contains the error coefficients for each of the various sensors. While the memories are shown separately, it is understood that the memories can be located in memory  76  associated with the microcontroller  75 . The microcontroller of course determines which sensor is being scanned and therefore can go to a memory location whereby the error voltages or compensation coefficients are stored for that particular sensor. In any event, to make matters simple it is shown that there is memory associated with each sensor and the output of the memories are directed via multiplexer  82 . Therefore, when sensor  70  is being scanned, the output from memory  80  is directed to the microcontroller  75 . The microcontroller  75  operates to compensate each of the sensors according to the error coefficients as determined and as stored in the various memory modules. It is of course understood, that the memory block as shown in  FIG. 6  may be incorporated in the internal memory  76  of the microcontroller  75  or for example, each of the memory modules as  80  and  81  can be stored in a connector ( FIG. 4 ) and therefore directed to the electronics. The microcontroller, as indicated provides temperature correction using coefficients from the memory of the microcontroller  76  or from the external memory as memories  80  and  81  associated with multiplexer  82 . The compensation, as indicated, is described in detail in the above noted patent, namely U.S. Pat. No. 4,192,005. It is further understood that various other compensation techniques can be employed. As shown, the microcontroller  75  has an analog output  77  which provides the analog output associated with each sensor. The microcontroller can also convert the digital information received from the analog to digital converter  74  to a different form of digital output to be compatible with various digital circuitry such as the Ethernet or other digital formats. It is of course understood that the output of the analog to digital converter  74  is a digital signal which can be further processed by the microcontroller to provide another digital output on the digital bus  78 . The microcontroller can also take the digital output from the analog to digital converter  74  and convert it to an analog output after compensation of temperature coefficients. It is thus seen that the above noted system enables one to make multiple pressure measurements in a rapid manner. The major aspect of the present invention is being enabled to attach the sensors directly to a surface model and to make high accuracy measurements without sacrificing response in temperature or frequency. 
     It should therefore be apparent to one skilled in the art that there are many embodiments of the present invention that can be ascertained and which employ alternate structure. Thus for example, one can employ a special digital circuit in lieu of microprocessor and can combine the functions of the multiplexers utilizing other scanning techniques. It is therefore deemed that all such alternate embodiments be encompassed within the spirit and scope of the claims appended hereto.