Browse Prior Art Database

Mercury Column Position Sensor Using Capacitive Circuit

IP.com Disclosure Number: IPCOM000049033D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Dym, H: AUTHOR

Abstract

A capacitive circuit senses the position of a fixed length column of mercury in a dielectric tube. A first and a second driver electrode each encircle the tube for a length that includes the ends of the mercury column over the full travel of the column. The capacitive coupling of these drivers to the column varies oppositely as the column position changes. A third similar electrode between the first and second driver electrodes encircles a constant length of the column and has a constant capacitive coupling to the column. A circuit using capacitance measuring techniques signals the position of the column.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 78% of the total text.

Page 1 of 2

Mercury Column Position Sensor Using Capacitive Circuit

A capacitive circuit senses the position of a fixed length column of mercury in a dielectric tube. A first and a second driver electrode each encircle the tube for a length that includes the ends of the mercury column over the full travel of the column. The capacitive coupling of these drivers to the column varies oppositely as the column position changes. A third similar electrode between the first and second driver electrodes encircles a constant length of the column and has a constant capacitive coupling to the column. A circuit using capacitance measuring techniques signals the position of the column.

Fig. 1 shows a glass tube 2 having a column of mercury 3 and temperature- responsive fluids 4 and 5 in bulbs 6 and 7 at either end. As the pressure in the bulbs changes differentially, the mercury column is moved along the tube. The length of the column does not change. The tube has first and second driver electrodes 8 and 9, a sensor electrode 10, and two shield electrodes 11 and 12.

Fig. 2 shows the components of Fig. 1 as elements of a circuit.

A circuit represented schematically as a switch 14 switches the drivers between two terminals to produce on the mercury column a Temperature, signifying voltage that is a function of the column position, and a Reference voltage that is independent of the column position (because the sum of the capacitances is constant). The signal at electrode 10 is coupled to an...