Apparatus for determining the freezing point of a liquid on or from a road surface

US4383770A · kind A · utility

Assignee

• Boschung Mecatronic AG · CH

Inventors

• Marcel Boschung · Davos, CH
• Walter Zehnder · St. Antoni, CH

Key dates

• Filing date: Jul 9, 1981
• Grant date: May 17, 1983
• Expiry date: Jul 9, 2001

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N25/04
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A portion of the test liquid is placed in the middle of a cooling plate having a central recess in which a thermometer probe is embedded in a heat-insulating material. Two Peltier elements disposed beneath the plate are connected in series and can be energized via a switch or a relay contact, thus chilling the portion of liquid. The probe may be connected to a voltage source and to an oscillograph which displays the voltage drop caused by the cooling liquid in the form of a curve. In another embodiment, the probe is series-connected to a constant-current source, and the voltage drop is amplified and supplied to an analog-to-digital converter connected to a microprocessor which both initiates the chilling operation and orders the A-D converter to sample the voltage and supply the equivalent digital value to the microprocessor itself. This order is repeated at regular intervals so that digital values corresponding to the solidification curve of the liquid can be stored in the microprocessor and evaluated there upon termination of the chilling process in order to determine the freezing point of the liquid, which temperature is then digitally displayed.