Product category:
Linear Position Sensors
News Release from: Micro-Epsilon UK | Subject: LVDT transSensor
Edited by the Engineeringtalk Editorial
Team on 25 May 2005
Customised sensor is perfect fit for
cylinders
Moog is using a closed-loop-feedback customised inductive displacement sensor to acquire data on the exact positioning of the control pistons on its hydraulic proportional valves.
In hydraulic drives, servo and proportional valves are used to control the volume of hydraulic oil flowing through the pistons Displacement sensors can be integrated into the valves to ensure controlled movement and therefore an exact dosage of oil
Moog, a manufacturer of hydraulic drives and valves based in Germany, is using a closed-loop-feedback customised inductive displacement sensor from Micro-Epsilon to acquire data on the exact positioning of the control pistons on its hydraulic proportional valves.
The focus of Micro-Epsilon's sensor solution, and the primary reason why Moog chose to work with the company, was Micro-Epsilon's ability to develop a customised coil and to manufacture the product, including the tooling, at a low cost, using its high volume manufacturing division based in the Czech Republic, Micro Sensor.
This facility has the capacity to manufacture up to one million sensors per year, using fully automated winding, production and assembly techniques.
According to Chris Jones, Managing Director at Micro-Epsilon UK: "This enables a product with a volume of 20,000 pieces per year to be sold for less than Eur 15, which is very low cost for this level of accuracy and precision".
Guenther Schallmoser, OEM Sales Manager at Micro-Epsilon in Germany explained further: "Moog needs to accurately measure and monitor the exact position of the piston (or spool) inside its servo and proportional valves".
"The piston controls the flow of oil to the hydraulic cylinders".
"As the piston moves back and forth, drilled holes in the valve body are covered and uncovered".
"The piston is moved by a linear motor".
"Therefore, the sensors we supplied had to be high resolution and precise, of the noncontact type and be capable of dynamically measuring the position of the piston".
In the finished design, Micro-Epsilon's LVDT transSensor inductive displacement sensor is mounted on a pressure tube outside of the pressurised section of Moog's valves, which also contributed to a lower cost sensor solution.
As Schallmoser commented: "Inside the pressure tube is a moveable core, which is permanently attached to the control piston".
"This core acts as a passive position transmitter and has several technical advantages".
"First, the measurements are made without contact and so there is no wear".
"Second, the sensor is not subjected to pressure and was therefore constructed from a cost-effective engineering polymer, which can withstand temperatures up to 100C".
"We also supplied a special, flat cable".
The transSensor itself uses the LVDT (linear variable differential transformer) principle and consists of a primary and two secondary coils with a common, moveable magnetic core.
An oscillator electronics excites the primary coil with an alternating current of constant frequency.
As a result, alternating currents are induced in both secondary coils with amplitudes depending on the core position.
A displacement of the core yields a higher voltage in one secondary coil and a lower voltage in the opposite coil.
The difference between both secondary voltages is proportional to the displacement.
Micro-Epsilon's displacement sensors work with a free-moving plunger without any mechanical contact to the sensor body.
The plunger has to be fixed onto the target by a mounting thread.
As well as hydraulic valves, these types of sensors are being used for measuring and monitoring movement, displacement, position, stroke, deflection, transposition in machines, vehicles and other industrial equipment. Request a free brochure from Micro-Epsilon UK ...
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