ActiveX/COM Overview

Publish Date: Jan 16, 2013 | 42 Ratings | 3.83 out of 5 |  PDF

ActiveX technology has been around now for several years. What started as a fancy name for Visual Basic custom controls has spread throughout Microsoft's tools, from operating systems to desktop productivity tools to development tools. The real question now is "What does ActiveX mean for measurement and automation applications?" As a scientist or engineer, should you be aware of or concerned about ActiveX? In reality, ActiveX is becoming a bigger part of our core software development tools, so much so that you are probably already using some form of ActiveX technology right now without realizing it.

What does ActiveX represent - Reusable components, interapplication communication (a better dynamic data exchange), a method for performing distributed computing operations. It is a term loosely applied to many different Microsoft-based technologies for creating and using software components. Because of the broad use of the term ActiveX, it is difficult to understand what it means for a software tool to use or be compatible with ActiveX. For instance, ActiveX is used almost interchangeably with component object model (COM) and distributed COM (DCOM).

When will ActiveX/COM become important for computer-based measurement and automation?
Today, all of the popular development tools work with ActiveX. This gives you the ability to use ActiveX servers and controls (a.k.a. COM objects) from development environments such as LabVIEW, LabWindows/CVI, Visual C++, and Visual Basic. You are using Visual Basic today, you commonly use ActiveX controls such as the ComponentWorks set of controls for data acquisition, data analysis, and data presentation. In other development environments such as LabVIEW and LabWindows/CVI, ActiveX objects are used less frequently and are typically mixed with software objects packaged as dynamic link libraries (DLL), and standard LabVIEW VIs.

How does ActiveX/COM impact computer-based measurement and automation?
To date, the largest impact of ActiveX/COM has been from the OPC Foundation. The OPC Foundation has defined a set of standard COM interfaces for industrial control and data acquisition devices. Most suppliers of industrial data acquisition and control products now work with OPC. Products are either OPC clients or OPC servers. An example of an OPC server is the NI-DAQ device driver for National Instruments data acquisition hardware. Several instrument vendors of test and measurement equipment are also developing ActiveX interfaces for their instruments. National Instruments, as part of the IVI Foundation is chairing a sub-committee to define ActiveX/COM interfaces for IVI instrument drivers.

What should you do to take advantage of this technology?
ActiveX/COM technology is very powerful and useful, but also very difficult to develop. Consequently, the best way to take advantage of this technology is to use products from vendors that fully support this technology. All of the National Instruments development tools, LabVIEW, Measurement Studio, and TestStand, take full advantage of ActiveX/COM. And, through Measurement Studio for Visual Basic, National Instruments measurement and control hardware products have ActiveX control interfaces.

Related Links:
ActiveX and COM -- Part I
ActiveX and COM -- Part II

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