In the pantheon of great technical reference manuals—texts like Radar Handbook (Skolnik) or The Art of Electronics (Horowitz & Hill)—there exists a quieter, more specialized volume. Its spine is often cracked, its pages smudged with the fingerprints of three generations of engineers. It is the Synchro and Resolver Engineering Handbook from Moog Inc.
Many companies stopped printing their handbooks. But Moog, stubbornly analog, kept the Synchro and Resolver Engineering Handbook in print—or at least available as a PDF. Why? Because the real world is analog.
Because in motion control, as in life, the angle is everything. And nobody ever explained the angle better than Moog. This feature is a tribute to the technical writers, applications engineers, and analog designers at Moog Inc. who created and maintained the Synchro and Resolver Engineering Handbook—a work that continues to turn up on desks from Cape Canaveral to Shenzhen. Synchro And Resolver Engineering Handbook Moog Inc
The handbook was Moog’s bid to standardize the industry. Before it, every defense contractor had their own way of testing, specifying, and wiring these components. Noise margins varied wildly, compensation networks were treated as dark arts, and a resolver from one vendor might not talk to a servo amp from another. Moog’s engineers, led by a cadre of analog gurus whose names are now lost to corporate history, sat down and wrote the canonical text.
In a conference room in East Aurora, New York (Moog’s global headquarters), there is probably a worn copy on a shelf. And somewhere right now, an engineer is opening a PDF of that same handbook. They are trying to figure out why their resolver’s sine-cosine mismatch is 0.5% at 25°C but 1.2% at 85°C. They will find the answer in a footnote on page 4-17. And they will be grateful. In the pantheon of great technical reference manuals—texts
This is the story of that handbook, the technology it champions, and why, in an age of digital abundance, its principles remain utterly indispensable. To understand the handbook, one must first understand the components at its heart. A synchro is, in essence, a rotary transformer. It looks like a small, precision motor but behaves like an analog computer. When you rotate its rotor, it outputs a set of three voltages (or receives them) that encode the exact angular position of a shaft. No glass disks, no LEDs, no fragile optics—just copper windings and a magnetic field.
Moreover, the handbook teaches a mindset. It teaches that a position sensor is not a black box that spits out bits. It is an impedance network, a transformer with a rotating coupling coefficient, a source of quadrature error and harmonic distortion. To truly debug a motion system, you must think like the handbook: with a vector network analyzer in one hand and a deep respect for analog imperfections in the other. If you are lucky enough to find an original printed copy from the 1980s—spiral-bound, with a faded blue cover and the old Moog “M” logo—you possess a piece of engineering history. Flip to any random page. You will see hand-drawn figures, typewritten equations (with corrections in pen from some long-ago applications engineer), and a purity of purpose that modern documentation rarely achieves. Many companies stopped printing their handbooks
For over half a century, this handbook has been more than a product catalog. It is a Rosetta Stone for translating the physical world of rotating machinery into the precise, unforgiving language of electronic feedback. Before optical encoders became cheap and ubiquitous, before Hall-effect sensors saturated the market, the synchro and the resolver were the undisputed kings of angular measurement. And Moog Inc.—a company more famous for its hydraulics on fighter jets and amusement park rides—wrote the definitive text on how to wield them.
The answer lies in edge cases. When a resolver cable runs 50 meters through a factory with VFDs spewing common-mode noise, the handbook’s sections on “Shield Termination” and “Twisted-Pair Routing” become priceless. When a resolver’s output voltage sags because the excitation frequency drifted due to a cheap oscillator, the handbook’s graphs of “Output vs. Frequency” show you exactly how much error to expect. When you need to build a redundancy management system—three resolvers on one shaft, voting on position—the handbook’s discussion of “dual-speed resolvers” and “electrical zero alignment” is the only guide you’ll find.