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August 17th, 2017
A Compact New Non-contact Proximity Measuring System Provides Greater Speed without Sacrificing Precision

By Kevin Conlin, Kaman Precision Products


Manufacturing and design industries require increasing precision of measurement, and selecting the right non-contact proximity measuring system can be essential to a successful project that stays on time and on budget. Using a measuring system that is non-contact and employs eddy current sensors allows for high-accuracy proximity measurement even in rugged surroundings. Simple construction of a non-contact measurement system, including switched output which means fewer parts to order, assemble and calibrate, will shorten design, testing and development timelines. Factors such as accuracy, cost and set-up time become more important as the speed of business continues to increase.


Non-contact measuring with eddy current is well-suited to a diverse array of applications


Many instruments are available in the tech sensor market to measure position, distance, or vibration of an object. These can be placed into two basic categories: contact and non-contact. While contact instruments are suitable for many applications, they have a limited frequency response and can interfere with the dynamics of the object being measured. Where these factors are a concern, non-contact methods have advantages such as higher precision and less interference with the object that is measured.


As with any device, both contact and non-contact measuring technologies have a wide range of performance characteristics ranging from very low (on-off) to very high precision (nanometer resolution), depending on their construction. It is not only necessary to choose the correct technology, but also the correct level of performance for an application.


Selecting the right technology for a non-contact proximity measuring system will come down to environment and performance requirements. The primary three technologies used are capacitance displacement, laser displacement, and eddy current sensors. Kaman Precision Products (Kaman) uses eddy current sensor technology because of its broad, flexible application in multiple industry settings.


Eddy current sensors are well suited for all environments from inside internal combustion engines to semiconductor clean rooms, unlike capacitance sensors, which are influenced by anything that comes between the sensor face and the target. Eddy current sensors also have advantages over laser sensors in higher-temperature environments, as eddy currents can withstand higher ambient temperatures than laser sensors that have their electronics integral with the sensing head. Kaman’s KD-2446 non-contact high-precision measuring system utilizes eddy currents, operating on the principle of impedance variation caused by eddy currents induced in a conductive target by a sensor coil. This technology is capable of sub-micro inch resolution.


The KD-2446 may be used in a variety of applications using target materials such as ferrous steel, stainless steel or aluminum. Applications for the KD-2446 include displacement, vibration, sorting and event capture.

Opto-isolated switched output can save setup and calibration time


In addition to its high precision measuring capabilities (with resolution to 12 micro inches), the KD-2446 also offers opto-isolated switched output for process control, making it ideal for interfacing to PLC inputs, counters, timers or alarm circuits. The switch is integrated directly within its simple unit, eliminating the need to purchase additional equipment or wire into other components. This makes measuring simple and more rapidly executed.


Other key features of the KD-2446 non-contact measuring system


Beyond its simple construction, integrated features and low price-point, other key elements of the KD-2446 include:

  • variable voltage input (12 to 24 volts DC)
  • temperature tolerant sensors (up to 400°F)
  • high speed (10KHz analog output, 3.3KHz switched output)
  • very low switching hysteresis (< 1% on ferrous targets)
  • RoHS compliant


In addition, with its excellent sensitivity to small targets and high-speed switching, the KD-2446 is ideal for RPM sensing in harsh environments.


The advantages of having a ready-made non-contact measuring system versus custom


If precision is a priority for your project, this may involve procuring a custom-built system, which can be costly and take many weeks to assemble. However, if static resolution to 12 micro inches is acceptable, the KD-2446 may be a viable alternative to a more complex system. Unlike many non-contact high-precision proximity measuring systems available, the KD-2446 is user-friendly, pre-manufactured and can be set up by your team independently, saving valuable time when budget is an issue. An “off the shelf” option like the KD-2446 can also be helpful in getting a measurement process started, for example when a concept needs proving quickly and with reasonable accuracy.


A more standardized non-contact measuring system can also be helpful in facilitating the exploratory phase of any research or development project. There is less inherent risk in purchasing a lower-cost measuring system to determine whether an object can be measured at all. A low-cost option can avoid your team having to waste time with a long development process only to find out some element cannot be measured.


A ready-made system like the KD-2446 is also helpful when new materials are being utilized in a project, which is increasingly the case as innovation continues to explode across many industries that require non-contact measurement. It can be helpful to start with a product like the KD-2446 off the shelf to see what kind of data is possible to obtain. In some cases an upgrade to a customized system may be needed for greater accuracy, but in the interim has been saved and information has been gathered to move the process along. In many cases however, you may discover that the KD-2446 non-contact high precision proximity measuring system is everything your project needs.