Browse Prior Art Database

Magnetic Null Transducer

IP.com Disclosure Number: IPCOM000096751D
Original Publication Date: 1963-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Shew, LF: AUTHOR

Abstract

This electromagnetic device is for detecting the presence, absence or a change of magnetic field intensity. It also measures the position or velocity of a moving object.

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Magnetic Null Transducer

This electromagnetic device is for detecting the presence, absence or a change of magnetic field intensity. It also measures the position or velocity of a moving object.

Device 1 detects a slit 2 in a moving metallic member 3. Device 1 consists of three separate windings 4, 5 and 6 on iron or mu-metal cores. The primary winding 4 is AC excited and is positioned on one side of member 3. Secondary windings 5 and 6 are connected in phase opposition and are positioned on the other side of member 3. The axes of these cores can be aligned either in parallel or at an angle to each other.

The induced voltages in windings 5 and 6 vary with the position of the slit 2 due to eddy current effect. Since 5 and 6 are physically displaced and are connected in phase-opposition, by the principle of superposition a null or zero output voltage occurs. This is when the induced voltages in the two secondary windings are equal in amplitude and opposite in polarity. The outputs of the secondaries are demodulated and added. Such produces a waveform in which the zero cross over point corresponds to the location of the center of the slit halfway between the two symmetrical secondaries. In detecting this null by differentiation, a very accurate and reliable method for determining the position of a moving object is realized.

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