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TWiki > Haptics Web>StanfordHaptics > MultiModalTactileSensing > ThermalSensing>ThermalSensorTechnology (03 Sep 2005, KarlinBark)

  • using integral heating elements and thermistors [Russell88].

  • Caldwell and Monkman [Caldwell92, Monkman93] have used Thermo-electric coolers (TECs) - also known as Peltier heat pumps - as temperature sensing elements. Thermoelectric coolers consist of a series of semiconductor couples connected electrically in series & thermally in parallel, which are attached between two electrically insulated ceramic faceplates. The TEC is designed to pump heat from one ceramic faceplate to the other, but if used in reverse, a temperature gradient across the device produces a proportional potential; a measure of the relative temperature change. Thermal sensing devices, built from thermo-electric coolers have 90% response and 90% recovery times of 1.8 secs & 7.8 secs respectively, but the ceramic faceplates are too brittle to be useful on a robotic manipulator.

  • Monkman & Talyor [Monkman93] have also produced thermal sensing devices using ferroelectric crystal pyrometers, as used in Infrared security detector systems. This is covered with a simple electrically resistive heater element etched in PCB copper on a thin layer of film mounted on an opaque, thermally conductive material, as in 9. The device gives 90% response & 90% recovery times of 600mS & 1.8 secs respectively, according to Monkman, but gives only a relative temperature change, as shown below, and again is brittle.

  • [Someya05] - University of Tokyo (E-Skin) uses organic semiconductors that are heat-sensitive in a thin plastic film for temperature sensing

  • The Thermal sensor is composed of two miniature resistors embedded in thermally conductive rubber: one is for heating the sensor and the other is for detecting temperature variations. So, the sensor requires two phases: the heating phase and the measuring phase. In the heating phase the heating element is powered on, thus heating the sensor up to an appropriate temperature. In the measuring phase the heating element is powered off, the thermal sensor assembly is put in contact with the object surface and the NTC sensor measures the temperature versus time variations. This function is related with the thermal flow between the sensor assembly and the object. [D. Taddeucci97]

  • Thermostylus, a thermal display that was designed to be appended to the force-reflecting Phantom interface (Sensable Technologies), makes contact with the finger pad of the index finger when the Phantom is held in a three-jaw chuck grasp

  • most thermal sensing units used peltier effect heat pumps. [Caldwell96] specified that the response times were quick (no numbers) but notes that the test subjects said it felt realistic

 
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