DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] FIG. 1 illustrates a first preferred client/server relationship between a measurement instrument 100 or 102 and a remote computer 104 . The measurement instrument 100 , 102 may take a variety of forms, including that of various waveform measurement instruments such as: oscilloscopes, logic analyzers, spectrum analyzers, network analyzers, AC power source/analyzers, or medical instruments (e.g., cardiographs, patient telemetry systems, or respiratory or metabolic analyzers).

[0030] The instrument 100 , 102 may comprise any one or more of a number of different output buses, including a General-Purpose Interface Bus (GPIB), a VME Extensions for Instrumentation bus (VXI bus), an RS-232 serial bus, a universal serial bus (USB), or Institute of Electrical and Electronics Engineers 1394 bus (IEEE-1394 bus).

[0031] An appropriate cable (e.g., an RS-232 106 or GPIB 108 cable) couples the instrument 100 , 102 to an Input/Output Server (I/O Server) 110 .

[0032] The I/O Server 110 may be instrument specific, such as an I/O Server which communicates with a specific instrument (e.g., the Agilent Technologies E4407B ESA-E Series Portable Spectrum Analyzer) or instrument class (e.g., GPIB spectrum analyzers). Alternatively, the I/O Server 110 may be of a universal design, as taught in the U.S. patent application of Faust et al. entitled “Universal I/O Interface” (Ser. No. 09/275,276 filed Mar. 23,1999).

[0033] One purpose of the I/O Server 110 is to receive byte streams of commands via a particular network protocol, and then transmit the byte streams of commands to a measurement instrument 100 in a form which may be understood by the measurement instrument 100 . For example, when necessary, the I/O Server 110 might unwrap received byte streams of commands (e.g., SCPI commands) so as to hide network protocol specifics from a measurement instrument 100 .

[0034] Another purpose of the I/O Server 110 is to receive requests for instrument data over a network connection, read acquired byte streams of data from an instrument 100 , prepare the data for transmission via a particular network protocol, and then transmit the data to a client or group of clients which requested the data.

[0035] In some cases, the I/O Server 110 might determine how to process and/or format byte streams which are transmitted over the bus by referencing an I/O Software Library such as the Agilent Technologies Standard Instrument Control Library (SICL) 112 . If the I/O Server 110 is coupled to an instrument 102 via a GPIB cable, the I/O Server 110 might also determine how to process and/or format byte streams which are transmitted over the bus by referencing the National Instruments 488 (NI488) library 114 .

[0036] In FIG. 1 , the I/O Server 110 is implemented using COM (Component Object Model) objects, and Microsoft's Distributed Component Object Model (DCOM) specification is used as a basis for transmitting data between the I/O Server 110 and a client 104 (via a network connection such as a LAN (local area network) or Internet connection). However, DCOM is not platform independent. FIG. 2 therefore shows an embodiment of the invention wherein an I/O Server 110 communicates with a client 204 using Java's Remote Method Invocation (RMI). Java is platform independent.

[0037] To facilitate the client/server configuration illustrated in FIG. 2 , the I/O Server 110 communicates with a client 204 via a Remotable Java Interface 200 . Data transfers between the Remotable Java Interface 200 and I/O Server 110 may be made using the JDirect protocol. JDirect is a communication protocol developed by Microsoft. Alternatively, a Java Native Interface (JNI) protocol could be used in lieu of the JDirect protocol. JNI is a communication protocol developed by Sun Microsystems.

[0038] The Remotable Java Interface 200 is a Java class that extends UnicastRemote, throws remote exceptions, and exposes data in a form which is more compatible in Java (e.g., it performs marshaling and unmarshaling). The structure of the Remotable Java Interface 200 is largely defined by the Java language.

[0039] The client 104 , 204 with which the I/O Server 110 communicates may be hosted by the same computer which hosts the I/O Server 110 , or may be hosted by a remote client computer. The client 204 is preferably a Java applet, ActiveX control, plug-in, or other application which is designed to interface with a web browser such as Internet Explorer or Netscape Communicator. However, the client 104 , 204 may also be a stand-alone application. In a preferred embodiment, the client is a “thin client”, with data reduction and processing being largely or entirely performed by the I/ 0 Server 110 or yet another server (not shown).

[0040] With respect to the client 204 illustrated in FIG. 2 , Java's AWT (Abstract Windowing Toolkit) or Swing graphical user interface toolkits may be used to render a graphical display of measurement data which is received by the client 204 . AWT and Swing are libraries of Java graphical user interfaces (GUIs) that provide connections between a Java application and the native GUI (e.g., a web browser) on which the Java application runs.

[0041] The I/O Server 110 and Remotable Java Interface 200 may be hosted by a server computer which services a measurement instrument 100 , by a client computer, or by a measurement instrument 100 (though it is sometimes preferable that the I/O Server 110 and Remotable Java Interface 200 be distinct from the measurement instrument 100 so that the measurement instrument 100 does not have to devote resources to the processing burden which the I/O Server 110 and Remotable Java Interface 200 might impose on the measurement instrument 100 ). The I/O Server 110 and Remotable Java Interface 200 are shown to be hosted by a measurement instrument 103 in FIG. 3 . Note that an advantage to the client/server relationship illustrated in FIG. 3 is that there is no need for an I/O cable 106 , 108 or I/O Software Library 112 , 114 . Furthermore, there is no need for an additional computer on the instrument side for the purpose of hosting the I/O Server 110 and Remotable Java Interface 200 . Also, since the Remotable Java Interface 200 is incorporated into the instrument 100 , the Remotable Java Interface 200 can become the programming model for the instrument 100 in lieu of a typical string based protocol and interface such as GPIB or RS-232.

[0042] Similarly to the location of the I/O Server 110 and Remotable Java Interface 200 , the location of the client 104 , 204 may vary as necessary. While it is a basic principle of the invention that the client 104 , 204 not be hosted by the measurement instrument 100 , the client 104 , 204 may be hosted by a computer which serves the afore-mentioned server and Java interface purposes. However, in most cases the client 104 , 204 will be hosted by a computer which is remote from both the measurement instrument 100 , the I/O Server 110 , and if provided, the Remotable Java Interface 200 . Regardless of the physical locations of the client 104 , 204 , I/O Server 110 , and Remotable Java Interface 200 , the client 104 , 204 will preferably communicate with the I/O Server 110 or Remotable Java Interface 200 via a network protocol such as TCP/IP or NetBEUI.

[0043] In the remainder of this description, the I/O Server 110 and Remotable Java Interface 200 will often be referred to collectively as a server 218 .

[0044] In general, two forms of data flow between a client 104 , 204 , server 110 , 218 , and measurement instrument 100 , 102 : commands and data. Commands typically flow from a client 104 , 204 to a measurement instrument 100 , 102 , whereas data typically flows from a measurement instrument 100 , 102 to a client 104 , 204 .

[0045] Commands may take a variety of forms, depending on the exact nature of a measurement instrument 100 . If the instrument 100 is a spectrum analyzer, for example, the commands may comprise SCPI commands. As will be explained shortly, the client 104 , 204 preferably displays a graphical user interface 400 ( FIG. 4 ) through which commands may be entered. Entered commands may then be transmitted to a measurement instrument 100 via the measurement instrument's servers 110 , 218 , to thereby 1) configure parameters of the measurement instrument 100 from a possibly remote location, or 2) request data from the measurement instrument 100 . As will be discussed further, later in this description, a client's knowledge of its transmitted configuration commands may assist the client 104 in rendering a graphical display of measurement data.

[0046] Data may also take a variety of forms, but typically comprises data which is transmitted from an instrument 100 , 102 to a client 104 , 204 via the instrument's servers 110 , 218 . Data which is transmitted from instrument to client will be referred to generally herein as “instrument data” or “measurement instrument data”. Instrument data may also take a variety of forms. In the past, instrument data which has been transmitted over a network has largely consisted of “image data”. That is, a measurement instrument 100 has periodically dumped an image displayed on its external display screen to its output bus, and the image has then been transmitted over a network connection to a client 104 , 204 which has requested the image. Unfortunately, such an image transfer process necessitates the transfer of large amounts of data. For example, the transfer of a conventional spectrum analyzer screen image might require a transfer of 130 kilobytes (130 kb) of data. The generation and transfer of this amount of data places a significant processing burden on an instrument 100 . As a result, an instrument 100 will typically only be able to generate and transmit a relatively few number of screen images to a client 104 , 204 . It is therefore difficult for a client 104 , 204 to display data in real-time. Not only is the client's display likely to appear choppy, but the fact that a client 104 , 204 is only able to display 1 /n ^th of the images which are displayed by an instrument 100 means that there is a high probability that a viewer of the client's displayed images will miss short but critical events which are acquired and displayed on a measurement instrument's own display.

[0047] In accordance with the invention, “measurement data” is transmitted by a measurement instrument 100 in lieu of image data. Measurement data, in general, is data which an instrument 100 acquires from a signal source. Measurement data is preferably raw digitized data which has been acquired from a signal source, but may comprise data which has been converted or pre-processed prior to a measurement instrument's generation of image data. Measurement data may also comprise configuration parameters, such as settings under which signal data was acquired (scale factors; baselines; settings of an instrument's knobs, sliders, and buttons (whether programmed or manually input to an instrument 104 ); etc.).

[0048] Measurement data is transmitted to a client 104 , 204 (via a server 110 , 218 or servers) in response to commands which are issued by the client 104 , 204 , such as commands to transmit signal data, or commands which query an instrument's configuration parameters. Measurement data comprising configuration parameters may be used by a client 104 , 204 to assist in its rendering of a graphical display.

[0049] Measurement data is much more compact than image data because it provides coordinates for discrete points in a signal waveform (e.g., spectrum analyzer measurement data might comprise a number of corresponding amplitude and frequency readings, while other measurement data might comprise corresponding time and decibel readings, etc.). Image data, on the other hand, must comprise data for lighting every pixel on a display screen, which data often comprises graticule data, marker data, text data, color data, intensity data, GUI data, and so on. The measurement data which is used to generate portions of the afore-mentioned 130 kb spectrum analyzer screen image might consist of only 1600 bytes of data (i.e., 1.6 kb; or two orders of magnitude less data than the spectrum analyzer's image data). Such a savings in the amount of data which a measurement instrument 100 needs to transmit to a client 104 , 204 provides numerous advantages.

[0050] A first advantage of smaller data transmissions is that the transmission processing burden which is placed on an instrument 100 is greatly reduced. A measurement instrument 100 can therefore provide data to its servers 110 , 218 more quickly, and with more regularity. Likewise, if a measurement instrument can prepare data for transmission more quickly and more regularly, a client 104 , 204 is likely to receive transmitted data more quickly and regularly. The ability of a client 104 , 204 to display data in real-time is therefore increased. Items such as graticule data, marker data, text data, color data, intensity data, GUI data, and so on may be generated and displayed by a client 104 , 204 .

[0051] The transmission of measurement data may also relieve the data processing burden of some instruments 100 , 102 . That is, many measurement instruments 100 , 102 have their own graphical rendering capability, and some of these measurement instruments 100 , 102 have the ability to cease generating screen images when, for example, their dedicated displays are turned off. As a result, the display of an instrument 100 which sits in a lab which is visited infrequently may be turned off, thus freeing up a greater percentage of the instrument's processing resources for acquiring and transmitting data to one or more remote clients 104 , 204 .

[0052] Another advantage of smaller data transmissions is that freed processing resources may be used to 1) acquire data at a higher sample rate, and/or 2) transmit more of an instrument's acquired data to a client 104 , 204 . These actions respectively increase the likelihood that a measurement instrument 100 will capture a fleeting signal event, and increase the likelihood that the fleeting event will be broadcast to a client 104 , 204 for display. The availability and transmission of more data to a client 104 , 204 also increases the potential granularity and update rate of a client's display, thus enhancing a remote user's ability to view high-resolution data in real-time.

[0053] The above advantages of transmitting measurement data in lieu of image data are derived from the fact that measurement data packets are much smaller than image files. However, additional advantages are derived from the mere fact that measurement data is sent to a client 104 , 204 in lieu of image data.

[0054] By sending measurement data to a client 104 , 204 , the client 104 , 204 is free to generate a display which differs from that of an instrument's own display (i.e., an “alternate visualization”). In other words, the graphical rendering which is undertaken by a client 104 , 204 is independent of that which is undertaken by a measurement instrument 100 . For example, a client 104 might desire to display a persistence display at the same time a measurement instrument 100 is displaying only a single, most recently acquired waveform. However, given that a client 104 , 204 may be a high-end personal computer or workstation which has significantly more and faster resources than an instrument 100 , even more pronounced differences between the displays of an instrument 100 and client 104 , 204 may be achieved.

[0055] For example, a client 104 might wish to generate one of a number of complex and/or three-dimensional displays which the instrument cannot. One type of three-dimensional display is the waterfall display 600 ( FIG. 6 ). A waterfall display 600 is a display wherein a z-axis is used to denote historical time periods 604 , 606 of an acquired waveform. With the display of each newly acquired waveform 602 , previously displayed waveforms 604 , 606 are shifted incrementally along the z-axis. If waveforms 602 - 606 are displayed as rows of color-coded polygons, or if corresponding points of adjacent waveforms (e.g., 602 , 604 ) are connected to one another, then one viewing a waterfall display 600 can easily compare two or more copies of a waveform 602 - 606 to determine the differences between them.

[0056] Another form of three-dimensional display which a personal computer has the resources to generate is a spectrogram display 700 ( FIG. 7 ). A spectrogram display 700 displays data as if a viewer were suspended over the previously mentioned waterfall display 600 . The third dimension in this display 700 is therefore provided by changes in color and/or light intensities. Typically, the birds-eye view of a most recently acquired waveform 702 will be displayed horizontally along the bottom of a display 600 , with older waveforms 704 , 706 being shifted incrementally towards the top of the display 700 . A spectrogram display 700 is especially useful in helping a viewer to identify small transient signal sources, which show up as blocks of color which differ from the color of surrounding blocks. A spectrogram display 700 is also useful in helping a viewer to identify shadow signals (i.e., those that vary with respect to some other primary signal in the spectrum, yet are shifted by frequency and amplitude from the primary signal).

[0057] A complex display which an instrument 100 may be able to generate, but with limitations, is the persistence display 500 ( FIG. 5 ). A persistence display 500 adds a color or intensity dimension to a screen image, and displays historical time periods of a waveform 502 in colors or light intensities which vary from the color or light intensity of a most recently displayed waveform 504 . After a predetermined or programmed time period, a historical waveform 502 usually fades away or otherwise disappears from a screen image (although in an “infinite persistence” mode, historical waveforms 502 always remain on the screen in some form). A persistence display 500 is advantageous in that it helps a viewer discover anomalies and/or trends in a waveform. While some measurement instruments already have an ability to generate a persistence display, the ability to configure such a persistence display is often limited as to 1) the number of persisting waveforms 502 , 504 which can be displayed, 2) the time period over which a waveform 502 may persist, and 3) the intensity levels and/or colors in which persisting waveforms 502 , 504 may be displayed. However, the significantly greater resources of a personal computer enable the generation of a persistence display 500 with nearly limitless waveforms 502 , 504 , waveform colors and/or intensities.

[0058] In FIG. 4, a client 104 is shown to display only a single, most recent waveform 400 . However, even such a simple display is advantageous over what has been done before when a client 104 , 204 and/or an instrument's servers 110 , 218 are able to generate the waveform 400 displayed therein in lieu of a measurement instrument 100 generating same. In fact, even when a client 104 is programmed to mimic the display which a measurement instrument 100 is capable of generating, advantages may be obtained by offloading any graphical rendering tasks from the measurement instrument 100 .

[0059] The screen images of FIGS. 4 - 7 may be displayed by a variety of applications, one of which will be described later in this description. In a preferred embodiment, the screen images include a variety of controls, some of which are peculiar to the applications which generate the screen images (e.g., controls 402 - 418 ), and some of which are peculiar to controlling a particular measurement instrument 100 from which an application draws measurement data for displaying a waveform 400 , 500 , 600 , 700 (e.g., controls 420 - 442 ). Note that unlike past applications, which have displayed waveforms as portions of screen images received from a measurement instrument 100 , the applications which display the screen images shown in FIGS. 4 - 7 utilize measurement data (e.g., amplitude and frequency readings) to display waveforms 400 , 500 , 600 , 700 . Thus, the applications which display the FIG. 4 - 7 screen images determine the content and format of the various items displayed therein. In fact, even the methods of displaying the waveforms 400 , 500 , 600 , 700 are controlled by the applications. This is possible because the applications do not receive a waveform as part of an image, but rather receive only measurement data from which waveform images may be created. Although the applications do not rely on measurement instrument image data for creating screen images, the applications may receive configuration parameters from a measurement instrument 100 (e.g., in response to queries for same), and/or may rely on configuration commands which the applications transmit to a measurement instrument 100 , to assist the applications in rendering graphical displays of measurement data and/or screen images.

[0060] Yet another advantage of transmitting measurement rather than image data over a network is that a client 104 running on a remote personal computer and receiving measurement data from an instrument 100 over a simple dial-up Internet connection (or simple LAN connection) has a high probably of being able to display and update data on a screen faster than an instrument 100 can display and update the same data on its own screen.

[0061] The advantages of offloading image processing duties from a measurement instrument are even more pronounced when a client 104 is instantiated on a current model workstation which, for example, receives data over a digital subscriber line (DSL), T- 1 , or high-speed local area network (LAN) connection.

[0062] Another advantage of transmitting measurement data between an instrument and one or more clients is that a single client may be programmed to simultaneously render alternate displays of the same measurement data, or multiple clients may be programmed to render alternate displays of the same measurement data. In the latter case, different viewers of measurement data may independently view the same data in different or individually preferred viewing formats, and all viewers are not committed to the viewing preferences of a single, master viewer (i.e. the graphical rendering undertaken by any particular client is independent of that undertaken by any other client, and independent of the viewing limitations of a measurement instrument). For example, the same or different clients might simultaneously display two different views of the same measurement data, with one view being a persistence view 500 , one being a spectrogram view 700 , etc.

[0063] A measurement instrument 100 , server 110 , 218 and client 104 , 204 may be programmed to perform the above tasks, either independently and/or with user input, via a number of computer readable media having program code stored thereon. The media may comprise magnetic media such as floppy disks or magnetic tapes, optical media such as compact discs (CDs), hard disks, etc. The program code stored thereon may comprise software (e.g., C++ program code, Java program code, etc.), firmware, etc. Depending upon its end-use, and the manner in which it is sold, the program code may be embodied in 1) a single application, or 2) a collection of applications, applets or the like which are designed to interface with one another. For example, the program code may be sold as a single application (e.g., packaged and/or sold as a single unit, or under a single license) which may be loaded onto a client 104 , 204 . The single application may then communicate not only with the client 104 , 204 , but also with a measurement instrument 100 via its servers 110 , 218 , to accomplish programming of same. Alternately, the single application may distribute portions of its code to the measurement instrument 100 and/or its servers 110 , 218 so that the distributed portions may run locally on the measurement instrument 100 and/or its servers 110 , 218 as the client portions of the application communicate with same. As another example, portions of the program code may be pre-loaded onto a client 104 , 204 , measurement instrument 100 and measurement instrument servers 110 , 218 so that portions of the program code may be sold with a physical piece of hardware. When one has upgraded a system to include all portions of the hardware (e.g., a client computer 104 , a measurement instrument 100 , and a server 218 ), the program code may then be used for its intended purposes.

[0064] The waveforms 400 , 500 , 600 , 700 which form part of the screen images illustrated in FIGS. 4 - 7 may be displayed by a variety of applications. However, by way of example, the waveforms 400 , 500 , 600 , 700 are shown to be displayed by a web browser. Although the web browser interface which is illustrated in FIGS. 4 - 7 is generic in form, one of ordinary skill in the art will readily appreciate that the items displayed in FIGS. 4 - 7 could be displayed through any available web browser (such as Microsoft® Internet Explorer or Netscape® Navigator®).

[0065] As shown in FIGS. 4 - 7 , in addition to displaying waveforms 400 , 500 , 600 and 700 , the web browser may also display elements of a graphical user interface. As taught below, user input to these elements may be utilized to program the client 104 , 204 itself, a measurement instrument 100 , or a measurement instrument's servers 110 , 218 .

[0066] The upper two rows of text 402 , 404 which form part of the web browser interface illustrated in FIGS. 4 - 7 display various conventional toolbar buttons such as File, Edit View, Help, Back, Forward, Stop, Refresh and Print buttons. Each of these buttons may be depressed to activate its associated function by using an input device (e.g., a mouse, trackball or pen tablet) which is designed for navigating over a graphical user interface. The third row of text 406 which forms part of the web browser interface illustrated in FIGS. 4 - 7 displays a text box 408 for entering the address of a web page, file or device (e.g., a measurement instrument 100 ).

[0067] A variety of buttons 410 - 418 which are specific to the page of data specified in the text box 408 are displayed on the lefthand side of the web browser interface. The Print Display 414 and Help 418 buttons are self explanatory. The Get Image 410 and Get Data 412 buttons respectively correspond to the functions of acquiring image data from a measurement instrument 100 or acquiring measurement data from a measurement instrument 100 . If the Get Image button 410 is depressed, then the image displayed between the lefthand 410 - 418 and righthand 420 - 434 buttons of the page being displayed by the web browser will be derived from an image which is generated by a selected measurement instrument 100 . If the Get Data button 412 is depressed, then the image displayed between the lefthand 410 - 418 and righthand 420 - 434 buttons of the page being displayed by the web browser will be generated from data which is transmitted from a measurement instrument 100 prior to the instrument's generation of an image which is based on the data. In this latter case, the image which is displayed by the web browser is preferably generated by the computer on which the web browser is running.

[0068] The System Status button 416 can provide, for example, 1) indications as to which clients 104 , 204 are connected to an instrument 100 , or 2) performance characterizations of measurements which are being transferred to a client 104 , 204 , etc. Performance characterizations may comprise information such as how many traces are being displayed or acquired per second. The System Status button 416 may also provide information which can assist a user in diagnosing issues pertaining to connecting to a measurement instrument server 110 , 218 .

[0069] Additional buttons 420 - 434 which are specific to the page of data specified in the text box 408 are displayed on the righthand side of the web browser interface. Many of these buttons are peculiar to the particular type of measurement instrument 100 from which the web browser is receiving data. For example, if the instrument 100 is a spectrum analyzer, these buttons might comprise Frequency 420 , Amplitude 422 , Bandwidth 424 , Sweep 426 , Markers 428 , Resets 430 and Options 432 buttons. Depressing one of these buttons 420 - 432 generates, for example, a pop-up window which provides functionality similar to that which is provided by the buttons, sliders and other controls which are often found on the face of a measurement instrument 100 .

[0070] Depressing the Commands button 434 generates, for example, a pop-up window 800 ( FIG. 8 ) with a text box 802 or selection screen through which various instrument configuration commands may be entered and/or selected. Entered or selected commands may then be transmitted to an instrument 100 through the instrument's servers 110 , 218 . The pop-up window 800 may further comprise a window 806 for displaying parameters, acknowledgments, and other data which are received by a client in response to transmitting an instrument command or commands (or in response to querying 804 the instrument for same).

[0071] The lower portion of the web browser interface shown in FIGS. 4 - 7 displays controls 436 , 438 , 440 , 442 which may be operated for the purpose of selecting the form of a waveform display (e.g., standard 400 , persistence 500 , waterfall 600 , or spectrogram 700 ), displaying a grid, displaying the perspective angle of a three-dimensional display, or pausing the update of a display.

[0072] Buttons 420 - 434 may function as display preference elements and/or command entry elements of a web browser. Thus, depending on the programming of a client 104 , 204 , the buttons 420 - 434 may serve to 1) receive display preferences from a user for the purpose of programming a client 104 , thereby changing the content of data displayed through a web browser, and/or 2) receive instrument commands from a user for the purpose of programming an instrument 100 or its servers 110 , 218 , thereby influencing the configuration of same (including the data transmitted by same). Note that like display preferences, instrument commands may also influence a client's display of measurement data.

[0073] While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art.