Displacement Transducers

Magtrol's line of Displacement Transducers provide contactless measurement of absolute piston position in hydraulic and pneumatic cylinders and other applications. Their robust construction, large insensitivity to shocks and very long life (due to no moving parts and therefore no wear of components) make them both cost effective and very reliable. Magtrol transducers offer a wide range of operational temperatures and admissible pressure resistance for even the most demanding applications.

The transducer provides a direct 4-20 mA output signal corresponding to the measuring range, as well as VDC temperature output. As an option Magtrol offers the CST 113 Signal Converter, which allows the complete chain to be calibrated according to the specific needs, either in current or voltage output.

Features

Large measuring range: Piston displacements from 50 to 1000 mm; 80 to 250 mm for DI 63X models
Current-based output signal (4 to 20 mA) for displacement
Built-in temperature measurement
Very long life: No moving parts and therefore no wear of components (Eddy-current principle)
Slim measuring system allowing large measuring range

Insensitive to metallic impurities in the working fluid
High shock and vibration resistance
Capable of withstanding pressures up to 450 bar
Robust construction, designed for permanent operation in hydraulic systems
EMC susceptibility conforms to European standards

Model Comparison

Version:	STANDARD TEMPERATURE	HIGH TEMPERATURE
Models:	DI 5XX	DI 605 / DI 610 / DI 611	DI 63X
Measuring Range	50 mm to 1000 mm	50 mm to 160 mm	80 mm to 250 mm
Operating Temperature	-40 °C to +80 °C	-40 °C to +125 °C	-40 °C to +200 °C
Displacement Output	4 to 20 mA	4 to 20 mA	20 to 4 mA
Temperature Output	7.5 VDC ±80 mV at 20°C	7.5 VDC ±60 mV at 20°C	7.5 VDC ±60 mV at 20°C

Operating Principles

Eddy-Current Principle
Magtrol Displacement Transducers use the principle of Eddy-current measurement. An aluminum tube moves along the transducer’s coil changing the induced Eddy-current losses, thus changing the coil impedance. An electronic circuitry housed in the transducer head, transforms the information of the measuring tube position into a linear signal. This circuitry uses modern SMD (surface-mounted device) technology, giving it robustness and reliability. The sensor is actively compensated for temperature changes.

Characteristics of the Output Signal
DI Series Displacement Transducers have a basic 3-wire configuration, providing a 4–20 mA current (20–4 mA for DI 63X models) proportional to the position of the aluminum tube. An indication of the temperature within the probe is also provided as a voltage output. In closed-loop systems, a specific piston position can be repeatedly achieved with a precision better than 0.05‰ full scale (i.e. better than 50 µm for a measuring range of 1 m).

EXAMPLE: DI 505–516/011 and DI 605–611/011 Transducers

Oscillating magnetic field created in the coil (4 kHz, up to 10 kHz depending on the measuring element and/or range)
Eddy current generated in the aluminum tube
Coil impedance increases when tube moves
Measure of inductance variation
Current remains constant
Demodulated signal transformed into 4–20 mA

Applications

The DI series of displacement transducers were developed principally for OEM applications in the hydraulic industry. They enable the direct and reliable measurement of the position of:

Servo Controls

Control Valves

Their design is such that the installation cost is kept to a minimum. This cost-effectiveness results from the limitation to one fixed standard signal of 4 to 20 mA with very precise determination of the measurement interval (from 0 to full scale) on the sensing element.

Hydraulic Cylinder

Displacement sensors are mounted inside hydraulic cylinders. The sensors are highly resistant to vibration, pressure (up to 450 bars) and have an excellent behavior on thermal compensation.

Boat Propeller with Variable Pitch