Providing the Ultimate Solutions in Precision Displacement Sensors
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Providing the Ultimate Solutions in Precision Displacement Sensors
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Advantages Versus LVDTs and Linear Potentiometers, Resistive Characteristics |
Position Measurement & Control - Issue 38
APPLICATION FOCUSFirstmark Controls Position Transducers: Small Size, Light Weight Advantages Provided Over LVDTs and Linear Potentiometers One reason to use Firstmark Controls position transducer products is their small size and light weight. The realities of physics mandate that size and weight be considered in nearly every engineering design. This is especially true in the sensor, test, and instrumentation world. Because the significant aspect of cable-actuated position transducers is a stainless steel cable, Firstmark Controls products have an inherent size and weight advantage compared to other choices.
Figure A1 - Size comparison of cable position transducers to rod-and-cylinder devices such as LVDTs and linear potentiometers Rod-and-cylinder products such as LVDTs, linear potentiometers, and magnetorestrictive transducers require room to store the rod and cylinder when the product is in its fully retracted state. For example, a typical rod-and-cylinder solution requires 42 inches (1.07 m) of operating space to measure 20 inches (0.51 m). A Firstmark Controls product can measure the same distance using less than 22 inches (0.56 m). When fully retracted, the rod-and-cylinder product takes up over 20 inches (0.51 m) of linear space. The Firstmark Controls product takes up less than 2 inches (0.05 m). Correspondingly, a rod-and-cylinder design will weigh significantly more than the Firstmark Controls product. A representative comparison for products with a 20-inch (0.51-m) range show rod-and-cylinder designs weighing 22 to 32 oz. (0.62 to 0.91 kg) while the Firstmark Controls product weighs around 3 oz (0.09 kg). While a non-contact sensor may seem to provide slight size and weight advantages over a cable position transducer, often that advantage is outweighed once the non-contact sensor electronics and signal conditioning are taken into account. PRODUCT FOCUSPotentiometer Resistive Characteristics Wirewound Versus Hybrid Versus Conductive Plastic Firstmark Controls uses precision potentiometers as one type of sensing device in our position transducers. Historically, potentiometers used wirewound resistive elements that produced finite voltage resolution of 0.003% to 0.3% of full scale. With this type of performance, potentiometers gained a reputation of solid although limited accuracy and modest lifetime devices. The development of hybrid and conductive plastic (thick film) resistive elements has resulted in potentiometers that can deliver infinite resolution and long life. The table below summarizes performance characteristics of each of these resistive technologies. Unless otherwise requested by the user, Firstmark Controls potentiometer-based products use only conductive plastic (for single-turn products) or hybrid (for multi-turn products) potentiometers. Resistive Technology Comparative Table
PRODUCT FOCUSPrice: Options and Life-Cycle Costs Benefits - Costs = Value Like most other purchases you make, the choice of a position transducer involves assessing the cost of the product in relation to other choices available. If you find yourself evaluating Firstmark Controls products against other choices, you may want to keep the following Firstmark Controls position transducer option and accessory prices in mind:
NC - no charge; * - provided standard In addition, Firstmark Controls products have several features that reduce your life-cycle cost:
Finally, our quick-response capability usually lets us ship to you within 7 days of your order and, in emergencies, often the same day. This results in more project planning flexibility, quicker implementation, and lower downtime for you. NEWS YOU CAN USEPrevious Issue (Issue 37)
ISSN 1527-5108 • Document Number S050X(040915) |
