Non-contact linear position sensors offer benefits for exporters

Variohm EuroSensor, the exclusive UK distributor for Novotechnik, presents an application note on non-contact linear position sensors that replaced potentiometer types for a tube processing machine manufacturer.

Depending on the application and the respective operating conditions, non-contacting measuring procedures are used for detecting linear movements; inductive linear transducers are often specified. Compact dimensions and integrated electronics, which render the measured value as an absolute, standardised current or voltage signal at the output, are important arguments for the usage of these linear position sensors.

Image
Uniflex Hydraulik GmbH, based in Karben, Germany, manufactures various tube production and processing machines. Compact dimensions, high pressures, quiet and reliable operation, as well as high flexibility, are characteristics of the hose crimpers (pictured right), which are successfully deployed in industry and workshops around the world. Here the machines have to rely on dependable position sensors because the press stroke must be adjustable to the respective tubular form and size according to the values set by the control.

Hubert Poth, in the Development, Software and Electrical Engineering department at Uniflex, explains: "For a long time, linear conductive plastic potentiometers did a good job measuring the travel at the press lever. With regards to accuracy, reliability and durability, we were very satisfied with this type of sensor from Novotechnik and have no reason to be critical."

But in the long run, it was not always easy to deal with the functional principle of the potentiometer. This type of sensor operates as a voltage divider, so different input voltages always have an effect on the measuring signal. Poth adds: "This is a disadvantage, which plays a role especially in export machines, since we often do not know where in the world our hose crimpers end up being deployed and what type of supply voltage the sensor technology must tolerate."

A practical alternative was found when Novotechnik developed a new linear position sensor series with integrated electronics, which helped to solve this problem.

Integrated signal processing

Image
The LS1 series of linear position sensors work on an inductive principle, but are in size completely compatible with the T-series potentiometers previously used with hose crimpers. With dimensions of 18mm x 18mm and effective lengths from 25 to 200mm, they are appropriate as alternatives to most standard potentiometers with a square cross-section. The integrated signal processing of the inductive linear position sensor makes the measured value available as an absolute current or voltage signal at the output. Poth confirms: "In our machines, we use the analogue 0...10V voltage signal; the sensors' wide input voltage range of 16 to 30V particularly benefits our export machines."

The integrated teach-in function with LED status display is particularly practical for many application types. By pressing a pushbutton directly on the linear position sensor, the user can choose zero and end points of the measurement, invert the measurement output slope, or set the desired signal amplitude. Unlike potentiometers, there is no need for a separate signal conditioner; as a result, control is simplified and the user does not have to get involved in the control program. Poth adds another advantage: "An auxiliary signal conditioner also requires its own installation slot and must be mounted and connected." Furthermore, any additional component in a machine or installation translates into a potential source of error.

The linear position sensors are also easily installed, as Poth explains: "Mounting brackets are included in the delivery, and a ball coupling without play allows for a shear force-free application, even with parallel and angular displacement of linear sensor and measuring direction." With its compact design and actuating rods on both sides, this series is also suited for a variety of other industrial applications.

These linear position sensors are virtually maintenance- and wear-free due to the contactless inductive measurement principle and offer high repeatability (up to 2mV and 3uA, respectively) and linearity of better than +/-0.15 per cent of the measurement stroke. The update rate of the output signal is specified at approximately 1kHz, which is more than sufficient for most applications. It is also advantageous for many applications that the inductive linear position sensor is completely unaffected by magnetic fields. The functionality of the wear-free alternative to potentiometers is easy to understand.

The inductive measurement principle

A sinusoidal and a cosinusoidal conductor loop are both located on the printed circuit board along the measurement stroke and are supplied with alternating currents with a phase-shift of 90 degrees. This generates alternating fields perpendicular to the printed circuit board, while their strength over the measurement area is also sinusoidal and cosinusoidal.

The result is a signal with a phase shift that is directly proportional to the stroke. The position indicator, designed as an oscillating circuit, 'floats' over the signal conducting plate. Its resonance frequency is tuned to the emitting frequency of the two signal feeds. The oscillating circuit is stimulated by them and emits its alternating field back to the printed circuit board. The rectangular receiver coil that is integrated into the circuit board receives this signal and sends it to the evaluation electronics. There the received signal is compared with the transmitted signals. The resulting phase information is then transformed by the integrated evaluation electronics into analogue position information, which is linear over the measurement range.

Poth concludes: "The fact that the inductive linear position sensors work non-contacting and therefore without any mechanical wear is of course a nice bonus for us, even though we were very happy with the reliability of the conductive plastic potentiometers."

Follow the link for more information about Novotechnik non-contacting linear position sensors from Variohm-EuroSensor.

Variohm-EuroSensor Ltd

Williams Barn
Tiffield Road
Towcester
NN12 6HP
UNITED KINGDOM

+44 (0)1327 351004

sales@variohm.com

www.variohm.com

More applications
3 hours ago
Mouser Electronics receives TDK’s top distribution awards
Mouser Electronics has received three top distribution awards from TDK. Mouser was honoured with TDK’s Global Best Performance Award for Fiscal Year 2022, North America Distributor of the Year for Calendar Year 2021, and European Distribution Award in High-Service Distribution for 2021.
13 hours ago
White Paper addresses assembly challenges
Resolve assembly challenges instantly with Henkel’s new high performance LOCTITE 402, an innovative instant adhesive that also improves workplace safety. Download the all-new white paper here.
22 hours ago
Schaeffler organises worldwide Climate Action Day
June has seen Climate Action Day at all Schaeffler locations worldwide, with every one of the approximate 83,000 Schaeffler Group employees stopping work for 90 minutes to focus on climate issues.
1 day ago
Yokogawa helps Solar Team Twente to solar challenge win
Yokogawa’s WT5000 precision power analyser has been used by Solar Team Twente to win the first ever Solar Challenge Morocco. The WT5000 helped the team to squeeze every last watt out of its car’s solar power system, ensuring it crossed the finish line of the 2,500 km course in first place.
1 day ago
HVACR OEM relies on Emka locking technology
When HVACR OEM Hansa Klimasysteme needed new connecting elements for the corners of its air-conditioning units to stabilise the housing cube, suitable for die-casting, it turned to Emka.
1 day ago
LEM holds inauguration ceremony for new production plant
Electrical measurement specialist LEM has held an inauguration ceremony in Penang, Malaysia for its new production plant. The ceremony marked a major step in the plant’s construction with the first electric current sensor products expected to come on-line in Q1 2024.
2 days ago
ITI acquires digital manufacturing specialist Cimlogic
ITI, one of the UK’s largest independent systems integrators, has acquired Cimlogic, a leading digital manufacturing solutions and services provider to some of the world’s largest manufacturers.
2 days ago
Atlas Copco saves precision sheet metal manufacturer over £6,000 a month
When Constant Group, a Manchester-based supplier of sheet metal parts, components, and fully assembled fabrications pieces were let down by their previous service provider for onsite high-pressure nitrogen generation, they turned to Atlas Copco for help.
3 days ago
Timber plant reduces downtime with NSK linear guides
Thanks to the adoption of NSK’s linear guides with K1 lubrication units, a timber manufacturer managed to reduce conveyor downtime by a factor of more than 12, prompting annual cost savings of more than €77,000.
3 days ago
Renishaw announces investment of over £50 million for UK site
Renishaw is to invest over £50 million at its Miskin site in South Wales to increase manufacturing capacity and to help meet its Net Zero emissions targets.

Login / Sign up