Technical White Papers

Ultra-Slow Motion Control

When design engineers use the term ‘motion control’, one’s first reaction is to perhaps think of high speed systems with rapid changes in direction and speed. Certainly, high speed, highly dynamic motion control applications have their own technical challenges but this is also true at the other end of the spectrum with very slow speeds. Tight control of slow speed is an important issue for many motion control applications such as industrial test and measurement, specialist automation, weapons systems, telescopes, CCTV cameras, security and surveillance systems to name but a few. This article looks at ultra-slow speed motion control and, in particular, the critical role of position or speed sensors.
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Position Sensors – A Dummy’s Guide

This paper is for engineers, technicians and students – especially those who need to get up a learning curve quickly and gain a basic understanding of position sensing and position sensors.
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Optical Encoders Versus Inductive Encoders

With so many position technologies to choose from it is unsurprising that design engineers have difficulty in selecting the right kind of sensor for their project. This article explains how optical and inductive encoders work and examines their relative strengths and weaknesses.
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An Encoder Trade Secret Revealed

This technical article, from Dr. Darran Kreit, Technical Manager of the global sensors company, Zettlex, sheds some light on a trade secret which has become an unfortunate and widespread aspect of ‘specmanship’ in the rotary sensor and angle encoder industry.
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Why Some Encoders Don’t Like Winter

There are a number of signs telling us that winter is drawing to a close and spring is just around the corner. New born lambs; trees suddenly coming in to bud and lots of Zettlex sales enquiries starting with “…this last winter’s been really tough – have you got something that can replace our optical encoders?” This article investigates why optical and capacitive encoders aren’t suited to winter conditions and suggests some possible solutions and alternatives.
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‘Shapeability’ for Custom Position Sensor Requirements

What happens when you are making a piece of kit, or even worse have designed, built and launched the machine, and the position sensor becomes unreliable? As frustrating as this issue is for engineers, when using traditional position sensing methods it does happen, particularly for applications in harsh environments. This article discusses the challenges engineers face and introduces a new generation inductive technique that they can rely on.
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Direct Drives & Direct Sensors

Direct drive motors have been around for many years but it seems that it is only very recently that equipment manufacturers and system integrators have grasped the advantages of this technique. This article compares and contrasts the use of direct drives to more traditional motor arrangements; highlights the relative advantages and discusses some difficulties and solutions.
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A Comparison of Inductive and Capacitive Position Sensors

Some inductive and capacitive position sensors can look quite similar and so it is no surprise that design engineers can find the differences between them confusing. Both use a non-contact technique to measure position and both can be built using printed circuit boards. Nevertheless, the basic physics, on which each type of sensor relies, is quite different. Ultimately, what this means in practice is that each type is suited to particular applications. This article explains the physics behind each technology and compares the consequent strengths and weaknesses of each approach.
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SSI – A Masterclass for Engineers Choosing a Position Sensor

This paper describes the Synchronous Serial Interface (SSI) used by many position sensors and controllers. It is aimed at electrical or mechanical engineers who are designing a position sensing systems and want to understand how SSI works and gauge its merits, without getting too deeply in to the bits and bytes.
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Position Sensors for Safety Applications

This paper describes a general design approach for position sensors in safety related applications, covering self diagnostics, built-in-test and duplex sensor arrangements.
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Position & Speed Sensors for High Vibration Environments

Machines that are subject to harsh or prolonged vibration present challenges for many components - none more so than position and speed sensors. In this article, Mark Howard of Zettlex, lists 10 simple rules for design engineers selecting position and speed sensors that must cope with shock or vibration.
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Angle Conversion Tables

We have compiled a series of look-up tables to help engineers convert between the most common angular units. This is particularly useful when specifying requirements for a new angular position sensor.
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Why do engineers dislike potentiometers?

Potentiometers have been around for a long time and are still, by far, the most commonly used position sensor. So why does every design engineer seem to be looking for a non-contact alternative? Mark Howard from Zettlex Ltd. examines this phenomenon and explains the pros and cons of potentiometers.
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Traditional Inductive Position Sensors versus New Generation Zettlex Sensors

Inductive position transducers such as resolvers and linear transformers have been the preferred choice for harsh environments and safety-critical applications for more than 50 years. However, a new generation of inductive transducers is now gaining in popularity. Mark Howard of Zettlex Ltd describes why inductive transducers are chosen for the toughest jobs, how they operate and why a new generation of inductive devices is taking over.
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The True Cost of Potentiometers

Potentiometers are still, by far, the most commonly used position sensor. They are widely seen as the low cost solution for many position sensing applications. But is their reputation for low cost justified? Mark Howard from Zettlex Ltd. takes a holistic view on the cost of potentiometers.
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Tandem Encoders

'Tandem Encoder' is a new term but one which is increasingly being used by mechanical and electrical designers. This article explains what a Tandem Encoder is; how they work; their technical features and where they are best utilized.
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Specification of Angle Sensors

Do you know your arc-seconds from your gradians? Angle sensors are generally rated and, just as importantly, priced according to their measurement performance. But performance is stated in a variety of ways and some manufacturers confuse matters by using crafty ‘spec-manship’. Mark Howard of Zettlex explains some of the terminology and provides an explanation of how to specify an angle sensor that is right for your application.
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Resolvers, Optical Encoders and Inductive Encoders

Resolvers are good. Encoders are good. But which is the best? There's only one way to find out...this article examines the strengths and weaknesses resolvers, optical encoders and inductive encoders and also offers some alternatives.
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Measuring the Rotation Angle of Large Diameter Shafts

Traditional rotary encoders can be readily fitted to shaft diameters of less than 2 inches, but what happens if your design needs a much larger diameter through shaft or bore? Mark Howard of Zettlex Ltd describes the traditional approach and a new, robust, more accurate approach using inductive sensors.
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Measuring Position or Speed in Harsh Environments

Harsh environments come in many forms but their common feature is that they place heavy demands on control equipment. The failure of position or speed sensors in the field can have a massive technical or commercial impact. If you are the engineer that specified the sensors in the first place, sensor failure might also have an impact on your career. So how do you make sure your sensors won’t let you down when the going gets tough? Mark Howard from Zettlex Ltd. examines the options.
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Inductive Versus Magnetic Position Sensors

Both inductive and magnetic sensors are the design engineers preferred choice for measuring position in harsh environments. Both offer the advantages of noncontact sensing over the traditional potentiometer. This paper describes the fundamental physics behind each technique and outlines the consequent strengths and weaknesses of each approach.
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Incremental versus Absolute Sensors

Most engineers still specify incremental position sensors because they think absolute versions are too costly. But the market has changed in recent years. Mark Howard, General Manager of Zettlex Ltd provides an up-to-date review of the relative merits of incremental versus absolute approaches.
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How Inductive Sensors Work

Inductive sensors are often used to measure position or speed, especially in harsh environments. For many engineers, inductive position sensor terminology and techniques can be confusing. In this article, Mark Howard of Zettlex explains the various types of inductive position sensor; their operating principles and their strengths and weaknesses.
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Everything You Always Wanted to Know About Slab Resolvers

The Chief Engineer says “We could use a slab resolver for that” and you say: “That’s a great idea boss” but you are actually thinking: “If I ask him what a slab resolver is I’m going to look like an idiot”. Sound familiar? If so, this article is for you – it explains what slab resolvers are; how they work; where to use them and suggests some lower cost options.
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Accurate Measurement of Shaft Speed

Measuring or controlling the speed of most rotating shafts is straightforward but significant problems can arise as soon as we start to talk about accuracy. Mark Howard from Zettlex Ltd. examines the issues involved and suggests some simple solutions to longstanding problems.
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Custom versus Standard Sensors

Why do some engineers choose custom sensors and others choose standard ‘off-the-shelf’ sensors? Often the right choice is not straightforward. Darran Kreit from Zettlex Ltd. examines the pros & cons of custom versus standard position sensors and explains why new technology is changing the rules.
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Choosing the right Position Sensor

With such a bewildering array of position sensors to choose from these days, how do design engineers ensure they select the right one? Mark Howard, General Manager at Zettlex UK Ltd, outlines the main types of sensor and their respective strengths and weaknesses.
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Are Optical Encoders as Accurate as you Think?

Zettlex encoders have recently been tested against what were, on paper, more accurate optical encoders. Here's what we found.
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Accurate Position Measurement in Varying Temperatures

Measuring position in a laboratory is usually carried out at a constant temperature to ensure accuracy but some equipment specifications require accurate position measurement over a wide range of operating temperatures. This is a much tougher challenge. Mark Howard of Zettlex discusses some of the issues and suggests 9 helpful hints for the design engineer.
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Accuracy, Resolution, Repeatability and All that Stuff

This article explains some of the terminology relating to measurement performance and why it’s important to understand the differences between accuracy, linearity, resolution, hysteresis and repeatability.
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