Patent Number: 059636106
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a simplified representation of a conventional nuclear reactor 10 of the type with which the inventive data acquisition system can be used. As shown therein, reactor 10 has a reactor core 12 and a representative two 14, 16 of a multiplicity of control element assemblies (CEAs), each movable by respective control element drive mechanisms 18, 20 through the reactor core. The drive mechanisms such as 18 and 20 are powered by an electronic power supply utilizing silicon controlled rectifiers and have power supply cables leading to a CEDM control cabinet (not shown) located in a cable spreader room (not shown). Means, 22 and 24, such as reed switch position transmitters, are responsive to the movement of the CEA shaft, for generating analog position signals indicative of the CEA position. Each position signal is delivered to a safety control system 30 which, after processing this input signal along with a multiplicity of other signals indicative of plant operating parameters, can generate safety trip signals for delivery to each of the CEA drive mechanisms 18, 20, whereby the shaft of every CEA is released. Turning now to the invention, systems 40 and 40' of FIGS. 2a and 2b, respectively, are general schematic representations of the first and second preferred embodiments of the inventive CEDM data acquisition system shown in combination with CEDM control cabinets such as those of the conventional nuclear reactor 10 described above. The primary difference between the first and second preferred systems 40 and 40' resides in the ability of system 40 to acquire all of the data associated with eight individual CEAs simultaneously, whereas the system 40' is only capable of acquiring data for a single CEA at any given time. Accordingly, system 40' is a more streamlined version of system 40. As shown in FIG. 2b system 40' includes a signal conditioning unit 44' and an associated computer 46'. Signal conditioning unit 44' and computer 46' preferably communicate with one another via a conventional data transmission cable. Signal conditioning unit 44' receives conventional analog coil-current signals from a conventional CEDM control cabinet 42' via a cable. Additionally, signal conditioning unit 44' receives analog position signals from a conventional reed switch position transmitter (RSPT) via a RSPT cable. Thus, within system 40' the flow of information is generally first into signal conditioning unit 44' and subsequently into computer 46' where the data can be manipulated by the user as desired. As shown in FIG. 2b computer 46' is preferably a lap top computer with a PCMCIA card for digitizing conditioned analog signals presented thereto by signal conditioning unit 44'. While the use of a lap top naturally offers the convenience of portability, a desk top PC with an analog to digital (A/D) conversion board installed therein could also be utilized with system 40'. Finally, signal conditioning unit 44' preferably includes a noise suppression network consisting of differential amplifiers and various filters with high common mode rejection to suppress unwanted electrical noise and to prepare the conditioned analog signals for delivery to computer 46'. Since those of ordinary skill in the art will appreciate how to implement the system 40' of FIG. 2b based on the following description of the more elaborate system 40 shown in FIG. 2a, the remainder of this specification will be primarily directed to describing system 40 of FIG. 2a. As shown in FIG. 2a system 40 is a more elaborate embodiment of the inventive data acquisition system which is capable of simultaneously receiving data associated with eight CEAs and eight associated RSPTs. As with the embodiment of FIG. 2b, the flow of information is generally into signal conditioning unit 44 and subsequently into computer 46. As shown, signal conditioning unit 44 and computer 46 transfer information via a conventional data transmission cable. Additionally, conventional CEDM control cabinet 42 is connected to signal conditioning unit 44 with eight cables (one cable per CEA being monitored). Finally, CEA position data is transferred into conditioning unit 44 for up to eight RSPTs simultaneously by using eight cables. Computer 46 can be either a desk top PC or a lap top PC with a cooperating docking station. In either case, computer 46 preferably utilizes Keithly Metrabyte Inc.'s personal computer (PC) analog to digital (A/D) conversion boards in order to digitize the conditioned analog signals entering computer 46 at a rate of about 500 samples per second. Additionally, computer 46 preferably includes a monitor for displaying the digitized signals presenting various display images of the digitized data acquired. Finally, conditioning signal unit 44 includes a noise suppression network consisting of differential amplifiers and various filters with high common mode rejection to suppress unwanted electrical noise originating from the CEDM power supply and to prepare the analog signals for the A/D conversion boards of computer 46. The software utilized to implement the system 40 of FIG. 2a is illustrated on a general level in FIG. 3. The preferred programming language for the software of FIG. 3 is Microsoft Visual Basic Version 4.0. Visual Basic Custom Controls (product VTX-DAS from Keithly Metrabyte, Inc. (VBX)) is preferably utilized to implement all of the data acquisition, data handling and data storage features of the inventive system 40. Additionally, a simple linking program to the Visual Basic Custom Control Program from Scientific Software Tools, Inc. (LABOJX Real Time Chart) is preferably utilized to implement the various graphing functions discussed further below. The software is compatible with the Windows working environment. Naturally, those of ordinary skill will recognize that many other programming languages and software options could also be used to produce the inventive system 40 without departing therefrom. As shown in FIG. 3, the inventive data acquisition system provides the ability to monitor, record and playback newly acquired data. The selection of entering a monitoring mode occurs at block 50 in which case the software then proceeds to block 52 where the data acquisition, data storage in a buffer and graphical display of the data begins. Once data acquisition has begun in block 52 the inventive system, optionally, monitors for a "rod-drop" event at block 58. Once a "rod-drop" has occurred, the display image can automatically change to display a rod-drop measurement screen at block 58 and the data acquisition process terminates. At any time during the data acquisition stage, the user has the option to freeze the display screen to measure the coil-timing and/or coil current, in which case the procedure passes to block 54. Once the data acquisition procedure has begun, the user has the option to permanently record the subsequently acquired data and the procedure passes through the record data block of 53. Also as shown in FIG. 3, the software of the inventive data acquisition system also has the ability to replay previously recorded data for subsequent analysis. The play back procedure begins at block 56 where the user selects to replay previously recorded data. The process then proceeds to block 57 where data is retrieved from the permanent memory, stored in a buffer and passed for graphical display at the monitor. Naturally, each play back terminates at block 58 once a "rod-drop" has occurred and the display image automatically changes to the rod-drop measurement screen. During play back, the user also has the option to freeze the screen at any particular point in time to measure coil timing and/or coil current, in which case the procedure passes to block 54. The stored data can then be replayed any number of times desired by repeating the playback process described above. A more detailed description of the software performance options of the system is illustrated in FIG. 4. As shown therein, the software component of the inventive data acquisition system begins when the software program is launched. A "splash screen" is briefly displayed and then the software displays a main menu which offers the user the options of either replaying a previously recorded trace, acquiring data and creating a new trace, configuring the program or quitting the program. During either the data acquisition mode or the play back mode, the software offers the user a variety of options for displaying acquired and/or recorded data. As can be seen by joint reference to FIGS. 4 through 5c, one display option available to a user includes simultaneous display of coil-current traces for the five coils associated with each CEDM. As shown in FIG. 5a, coil-current traces 61a-61e are recorded/played back at a rate of 300 samples per second with the Y axis representing the coil-current in amps and the X axis representing time in seconds. Mouse-activated buttons 61a'-61e' allow the user to select any one of the coil-current traces thereby freezing the screen and permitting the use of interactive cursors 63a-64b to measure coil-current and/or timing changes. Real time monitoring can be resumed by selecting the mouse-activated continue button 69i. The resulting coil-current and/or timing changes for the selected coil-current trace are displayed in data boxes 65a and 65b, respectively, for simplified and accurate data analysis. The display shown in FIGS. 5a-5c are preferably updated every second as traces 61a-61e progress leftwardly and the user has the ability to view the displayed data in either of the time-expanded (0.5 second, 2 second or 5 second scales) views by selecting mouse-activated buttons 69c. When it is desired that data for a single CEA be recorded/played back, the mouse-activated record rod button 69d can be selected. However, where it is desired that CEDM data for an entire rod-group (up to eight CEAs) be recorded/played back, the user selects mouse-activated, record-group button 69e. In such a case, buttons 68, representing each of up to eight CEDMs appear at the top of the display and become activated. Display 60 then shows coil-current traces 69a-69e for the coils of the selected CEDM and the selected CEDM number appears in box 65c for convenience. Naturally, any one of the other seven CEDMs can be monitored simply by selecting the desired mouse-activated CEDM button 68. As noted in FIG. 4 and shown in FIGS. 5a-5c, a user has the option of directing the inventive data acquisition system to monitor for a rod-drop event and to automatically change the display image upon occurrence of the rod-drop event. This feature is implemented on the display screen 60' of FIG. 5b by selecting the mouse-activated rod-drop button 69a during recordation. With rod-drop button 69a, thus, selected the reed switch position (CEA position) signal 62 will be displayed on screen 60' and the data acquisition system will preferably monitor the upper gripper coil-current trace 61b. Before the upper gripper CEDM coil-current has stabilized to a predetermined holding value (see FIG. 5a) no rod-drop event can occur. However, once coil-current trace 61b stabilizes (see FIG. 5b), trace 61b is monitored to determine whether the coil-current is either above or below the predetermined "holding current" value. If trace 61b falls too far below the "holding current" value (see FIG. 5b) a rod-drop event has occurred and display 60" will automatically change to display a rod-drop measurement screen 60'. The triggering event is depicted in display 60' of FIG. 5b and the resulting rod-drop measurement screen in 60" is depicted in FIG. 5c. As shown in FIG. 5c the rod-drop measurement screen 60" only displays the upper gripper coil-current trace 61b and the position (reed switch position) trace 62 as a function of time, the traces 61b and 62 being indexed on the initiation of the rod-drop event. Also as shown in FIG. 5c an "acceptance" trace 67 will be superimposed on the rod-drop measurement screen that will aid the user in determining whether the upper gripper coil performance is within proper specifications during the rod-drop event. Naturally, the rod-drop event data can be saved (see box 66' of display 60") and the user can return to the normal monitoring display 60 of FIG. 5a. As noted above, while an operational test is being monitored in real time, the user has the option of recording one CEDMs data, all eight CEDMs data and/or the rod-drop event data. Further, the user has the option of printing display data by selecting the mouse-activated print button 69f. Moreover, operational test data can be replayed any number of times by selecting the mouse-activated restart button 69h. Finally, a user may choose to quit the program at any time by selecting the mouse-activated quit button 69j. Turning now to the signal conditioning aspect of the system, the block diagram of one signal conditioning unit 70 of the inventive system is shown in FIG. 6. Signaling conditioning unit 70 receives unprocessed analog coil-current and/or reed switch position signals at the input 71 thereof. The signals then pass to the differential amplifier 72 and low pass filter 74 where elimination of extraneous noise introduced into the signals by the electronic circuit powering the CEDMs is removed. Preferably, the differential amplifier 72 is a single integrated circuit which is preferably an isolation amplifier with supporting circuitry designed to provide high common mode rejection at the lowest of the frequencies of the extraneous noise (about 300 Hz and above) to be removed. Low pass filter 74 preferably has a cut-off frequency of about 300 Hz so as to further reduce extraneous noise from signals passing therethrough. Use of the isolation amplifier as shown offers the highly desirable feature that voltage spikes, or other erroneous electrical signals, which may occur downstream in the system, are not fed back to the control element drive mechanisms. After being, thus, conditioned the analog signals pass through an output 75 to an appropriate computer such as computers 46 or 46' depicted in FIGS. 2a and 2b, respectively. A schematic representation of the preferred signal conditioning unit 70 is shown in greater detail in FIG. 7. As shown, integrated circuit 73 is preferably an isolation amplifier having supporting circuitry 77 selected to provide high common mode rejection at or about the frequency of the alternating current supplied to the CEDMs. Additionally, signal conditioning unit 70 provides a low pass filter which has a cut off frequency of about 300 Hz. This is lower than the frequencies of noise contained in the DC current supplied to the CEDMs, but higher than an AC ripple component of the DC power. The preferred integrated circuit 73 can be purchased from Burr-Brown as Model No. ISO 165 and is preferred for its low power and high electrical isolation characteristics. Additionally, the Burr-Brown ISO 165 provides for signal gain. The Burr-Brown ISO 103 (which is depicted in FIG. 7) is also an acceptable alternative isolation amplifier. However, it is less desirable than the ISO 165 because it is more expensive, consumes more power, generates more heat and does not offer signal gain. Also as shown in FIG. 6, the preferred supporting circuitry 77 includes a 20 ohm resistor 76 connected across the input terminals of integrated circuit 73. Resistor 76 provides the very advantageous feature of allowing the data acquisition system to be calibrated (to remove an offset component of the signals exiting the signal conditioning unit 44) without the physical manipulation of any components of the system. Instead, the system can be calibrated, without signal conditioning unit 44 (FIG. 1) being connected to the CEDM control cabinet 42, simply be selecting the appropriate option in the program main menu of the accompanying software. Resistor 76 does not otherwise effect conditioning of the signals entering input 71. A more extensive schematic of a complete circuit board containing, inter alia, a plurality of signal conditioning units 70 is shown in FIG. 8. As indicated by the use of comparable reference numerals, each signal conditioning unit 70 depicted in FIG. 8 should be understood to include the supporting circuitry depicted in FIG. 7. The circuit board 80 of FIG. 8 includes signal conditioning units for conditioning coil-current signals and reed position switch (i.e., position) signal for two CEDMs. Accordingly, the complete multi-rod data acquisition system 40 of FIG. 2a should be understood to include four nearly identical circuit boards 80. As shown in FIG. 8, five signal conditioning units 70 are allocated for the five coils of each CEDM and these signal conditioning units receive input signals via input connector 71'. An additional signal conditioning unit 70' is allocated to condition the reed switch position signals which enter unit 70' via input connector 82. It will be appreciated that removal of an offset component of the position signal exiting the signal conditioning unit 44 is not necessary. Thus, no calibration resistor 76 is included in signal conditioning unit 70'. However, an amplitude reducing resistor 83 is connected to the output of signal conditioning unit 70' in order to ensure that the signals exiting unit 70' are compatible with the digital to analog converters of the computer into which signals will be entering. It will be appreciated that the lower lefthand portion of FIG. 8 is a repetition of the upper lefthand portion of FIG. 8 and is dedicated to signal conditioning the signals acquired from another CEDM. Master circuit board 80 of FIG. 8 further includes means for receiving electric power 86 to operate signal conditioning units 70 and 70'. Also, an output connector 85' is utilized to connect a master oscillator 84 and a 5 volt regulator 87 of master circuit board 80 with the three other signal conditioning circuit boards. Similarly, an output signal connector 75' of each of the four circuit boards is in electrical communication with a downstream computer. The single master oscillator 84 generates identical synchronization signals 79 to operate all of the isolation amplifiers of system 40 in unison. While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiment, but is intended to cover the various modifications and equivalent arrangements included within the spirit and scope of the appended claims.