This Glossary of Terms is a compendium of words and expressions that has been collected over the years of teaching the principles of electrohydraulic motion control to students who have come mostly from industry.

As the course has evolved, and the more that I look at the technology, the more the similarities between hydraulics and electronics become apparent. In fact, the two technologies have tended to blend together, not in a confusing way, but rather, in an enlightening way. I have been known to absent-mindedly connect the emitter of a transistor to the tank or a pump inlet to electrical ground as I work at the boards during lectures. It is inadvertent, but I think the faux pas helps to demonstrate to the student that there are analogous functions in the two power/control media.

Such has been my method of teaching. Because the students come mostly from the ranks of practicing engineers and technicians, it is helpful for them to draw upon their experiences in fluid power to master the principles in electronics. And students have been generally appreciative of the liberal use of hydraulic concepts to bring home points about, for example, a transistor as being merely an electronic valve, or to illustrate how a variable displacement pump can be viewed as a power amplifier. It helps to bridge the gap between the two media.

What this glossary contains, then, is a brief technical definition of a number of those terms that are used on an almost daily basis by those engineers who work in the field of electrohydraulics and electrohydraulic motion control. Because the use of hydraulic analogies was helpful for hydraulic engineers and technicians to bridge the gap to electronics, it occurred to me that, perhaps, the use of electronic analogies and examples would help some electronic engineers and technicians to improve their skills in hydraulic systems.

The glossary contains both electrical and hydraulic terms that are used in the motion control industry. The intent is to have it serve as a cross-reference for those who may be skilled in one art, but who are interested in the other. In short, it is hoped that the compilation of terms can be used to "go both ways". The terms have been compiled over a period of more than ten years. Where I thought it might be helpful, I included cross-linking descriptions and analogies. In some cases, mathematical definitions are used if they were judged to contribute to understanding the definition.

It is intended that this be a living document, and as new terms emerge, as they tend to do in all technologies, they will be added in future editions. Comments and suggestions from readers and users are warmly welcomed.