Capacitance Sensor Systems

MTI Capacitance Sensors are designed to measure the thickness of insulating materials, such as glass, sapphire, several plastics and even semi-insulating semiconductor material including GaAs and silicon nitride with uniform dielectric constant and thickness <10 mm.

MTI’s new capacitance amplifier transforms gap capacitance directly to a digital target thickness. This direct conversion method removes errors that conventional analog amplifiers have due to linearization, analog filtering, range extension and the summing of channels to attain step or thickness measurements.

Users will only have to perform a rapid calibration, which takes under a minute, with a sample of the material that has a known thickness. MTI offers a comprehensive non-conductive material measuring system.

Its package includes a capacitance amplifier with up to 4 channels, a dieletric fixture, MTI special dielectric probes, and a smart software package with integral computing capability that eliminates the guess work from what was previously a difficult measurement.

The standard feature quadrature encoder input, offers probe positional data concurrently with its thickness signal. Capacitance thickness amplifiers used with quadrature encoders synchronize displacement measurements to the probe position to offer accurate surface profiles of several target types. Sample rate, linearization, filter frequency response, and probe range are all digitally controlled with the Accumeasure D series.

This guarantees highly accurate data capture, lossless processing and no need to buy extra acquisition hardware.

Key Features

The main features of the Capacitance Sensor Systems include:

  • Modifiable output data rate
  • Inbuilt calibration software
  • Extra acquisition hardware is not required
  • Accuracy of up to 1 µm
  • Lossless 24 bit processing
  • Analog output
  • Custom probes can be developed by MTI for specific application
  • Measures clear, translucent or opaque materials
  • Digitally monitored signal averaging, filtering and range
  • Interface with NI LabVIEW™
  • 100% digital linearization of the gap response
  • Capable of measuring both thickness and displacement of SiC, GaAs, silicon, glass, sapphire and other high bulk resisvity materials


Lasers sensors or other non-contact measurement sensors do not work with sapphire materials, glass, and plastic because of their clear and shiny surfaces, laser cross talk through the material, or cell/foam bubbles that ricochet the laser beam.

The material’s non conductive nature prevents the working of conventional eddy current gages and capacitance gages.

An electric field is emitted by MTI's capacitance probes and this field travels through the insulating material. The insulating material’s dielectric constant conducts that field.

The capacitive system can measure the thickness by accounting for varied dielectric constants through a calibration with the material to be tested. The calibration remains consistent as long as the material’s dielectric constant does not change.

Some of the other applications of the Capacitance Sensor Systems include:

  • Built-in computing capability
  • Thickness of foam
  • Measuring plastic thickness
  • Sapphire wafer inspection

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