See How An LVDT Displacement Transducer works.

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How it Works - 4 to 20mA LVDT
An LVDT Displacement Transducer comprises 3 coils; a primary and two secondaries.

The transfer of current between the primary and the secondaries of the LVDT displacement transducer is controlled by the position of a magnetic core called an armature.

On our position measurement LVDTs, the two transducer secondaries are connected in opposition.

At the centre of the position measurement stroke, the two secondary voltages of the displacement transducer are equal but because they are connected in opposition the resulting output from the sensor is zero.

As the LVDTs armature moves away from centre, the result is an increase in one of the position sensor secondaries and a decrease in the other. This results in an output from the measurement sensor.

With LVDTs, the phase of the output (compared with the excitation phase) enables the electronics to know which half of the coil the armature is in. 

The strength of the LVDT sensor's principle is that there is no electrical contact across the transducer position sensing element which for the user of the sensor means clean data, infinite resolution and a very long life.

An oscillator/demodulator circuit built into the displacement transducer is powered by and controls the 4-20mA output.
As the transducer contains internal signal conditioning electronics, there is no need for external signal conditioning.

Displacement Transducers - Pre-Calibrated, Easy to Install and Use
RDP’s LVDTs are designed for accurate displacement/position
measurement even under the harshest conditions. The new DCV DC-DC LVDTs offer a 0-10 volt output that is electrically isolated from the input (14-26 VDC) eliminating concerns over power supply selection and grounding issues. Available in measuring ranges from 0.2 inch (5mm) up to 37 inches (940mm). Ideal for machine tool, assembly equipment, civil engineering, materials testing, and OEM applications.

Hundreds of standard models and options or if required custom designed solutions.

Menu of Displacement Transducers

 The DCV LVDTs are ideal for use in:

  • Specialty machines
  • Industrial control systems
  • Material testing
  • Civil/structural engineering
  • General purpose testing/instrumentation


About RDP Group:
RDP has been manufacturing Transducers and Electronics for over 50 years. Their specialty lies in the field of measurement of physical parameters:
•Displacement Measurement Sensors
•Load Cells
•Pressure Transducers
•Signal Conditioning Amplifiers / Panel Meters for all types of sensors