Microstrain

Subminiature DVRT®

Subminiature DVRT®

Differential Variable Reluctance Transducer (or "half bridge LVDT")

Overview

Ideal for linear control and precision measurement applications, the Subminiature DVRT® provides fast response and rugged packaging. The Subminiature DVRT® features micron resolution, linear analog output, flat dynamic response to kHz levels, and very low temperature coefficients. Its free sliding transducer core is lightweight, strong, and corrosion resistant. Cores are precision ground to insure a close sliding fit within the open bore of the stainless-steel lined DVRT® body. This precision allows the DVRT® to achieve extremely high repeatability. The sensing head is capable of total submersion in aqueous environments. MicroStrain’s desktop consoles and in-line signal conditioners provide the Subminiature DVRT® with plug and play housing, power, analog output, LCD display, RS-232 output and software. A range of modular positioning attachments and custom strokes are also available.

Sensor Design

Core position is detected by measuring the coils’ differential reluctance using a sine wave excitation and synchronous demodulator. This differential detection method provides a very sensitive measure of core position while cancelling out temperature effects.

The transducers’ coils and Teflon® cables are sealed in vacuum-pumped epoxy, within the stainless-steel case. This provides outstanding environmental resistance. The DVRT® has been successfully employed in harsh applications, including short term immersion in saline and pressurized oil.

Units available for long term immersion, corrosive and high pressure environments can be custom built to meet such requirements

Sub-Miniature Displacement Sensor
Applications
  • miniature control elements for automotive and robotic systems
  • process control for production-line monitoring
  • dimensional gauging for quality control applications
  • measuring strain and deflection in materials science and civil structures
  • linear/angular positioning of optical components
  • miniature force, torque, acceleration sensors
  • measuring strain, micromotion and deformation in bone and tissue
  • available with sub-micron resolution and long stroke range
  • operating temperature to 175 °C
  • frequency response up to 20 kHz with DEMOD-DC
  • frequency response up to 8 kHz with DEMOD-DVRT
  • lightweight core will not influence frequency response
  • stainless steel and high-performance polymer design suitable for extremely harsh environments
  • waterproof, suitable for short term submersion in corrosive media such as brake fluid and hot saline
  • frictionless design suitable for high duty-cycle applications
  • easily customized to suit specific applications

Electrical Specifications
Obtained using DEMOD-DVRT® and DVRT® with 800 Hz low pass filter at constant temperature

Linear Stroke Lengths 4, 8, 24, 38 mm (standard resolution)
6 mm (high resolution)
500 µm or less (nano resolution)
Accuracy ± 1.0 % using straight line
± 0.1 % using polynomial
Sensitivity DEMOD® output / sensor range
Signal to noise 4200 to 1 (with filter 3 dB down at 800 Hz, standard resolution), 466 to 1 (unfiltered)
Resolution 1.0 µm for 4 mm stroke
2.0 µm for 8 mm stroke
6.0 µm for 24 mm stroke
9.5 µm for 38 mm stroke
0.6 µm for high resolution version
125 nm for nano resolution version (up to 10 nm resolution is possible with customized sensor range and electronics)
Frequency response 800 Hz standard, 20 KHz optional
Temperature coefficient offset 0.002% / ˚C (typical) span 0.030% / ˚C (typical)
Hysteresis ± 1 micron
Repeatability ± 1 micron

Mechanical Specifications

Overall body length 18.5 mm for 4 mm stroke
34.5 mm for 8 mm stroke
81 mm for 24 mm stroke
110 mm for 38 mm stroke
34.5 mm for high res version
34.5 mm for nano version
Outside diameter 4.76 mm (3/16 inch)
Housing material 300 stainless steel, smooth
5/16 - 24 threaded 400 stainless steel(optional)
Attachment method optional: magnetic mounting block, threaded body, clamping collar
Leadouts 45 cm multistrand, shielded, stainless steel reinforced teflon insulated cable
Connector keyed 4 pin Lemo, polyolefin relief
Operating temperature -55 to 175 ˚C
Core weight 500 µm: 0.04 g, 4 mm: 0.04 g, 6 mm: 0.04 g, 24 mm: 1.62 g, 38 mm: 1.67 g
Core material stainless steel
Cable diameter 0.070 “

Contact us for information on custom designs suitable for immersion, corrosive and high pressure environments.

Subminiature DVRT Starter Kit with Four Channels
Subminiature DVRT Starter Kit with Four Channels

S-DVRT-8-SK4
Includes (4) S-DVRT-8, (4) CBL1, (4) DEMOD-DVRT-TC, (1) MB-STD-4

Subminiature DVRT Starter Kit with Three Channels
Subminiature DVRT Starter Kit with Three Channels

S-DVRT-8-SK3
Includes (3) S-DVRT-8, (3) CBL1, (3) DEMOD-DVRT-TC, (1) MB-STD-4

Subminiature DVRT Starter Kit with Two Channels
Subminiature DVRT Starter Kit with Two Channels

S-DVRT-8-SK2
Includes (2) S-DVRT-8, (2) CBL1, (2) DEMOD-DVRT-TC, (1) MB-STD-4

8mm stroke Subminiature DVRT Starter Kit with One Channel
8mm stroke Subminiature DVRT Starter Kit with One Channel

S-DVRT-8-SK1
Includes (1) S-DVRT-8, (1) CBL1, (1) DEMOD-DVRT-TC, (1) MB-STD-4