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Temperature Compensation for Fluid Resistivity Measurements

IP.com Disclosure Number: IPCOM000080745D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Haskell, JW: AUTHOR

Abstract

An ink resistivity monitor is shown schematically in Fig. 1. Basically it comprises an alternating current Wheatstone bridge, in which the resistance of an ink resistivity sensor IS is compared to a calibrated resistance. To provide temperature compensation, one of the bridge arms is replaced by a standard resistor SR, whose resistance and temperature coefficient is identical to the ink sensor when the system ink concentration is correct. Instead of measuring the absolute resistivity, the monitor measures the system ink resistivity relative to the standard resistor. This relative measurement, expressed as a ratio, is independent of the ink temperature when both standard resistor and system ink are at the same temperature.

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Temperature Compensation for Fluid Resistivity Measurements

An ink resistivity monitor is shown schematically in Fig. 1. Basically it comprises an alternating current Wheatstone bridge, in which the resistance of an ink resistivity sensor IS is compared to a calibrated resistance. To provide temperature compensation, one of the bridge arms is replaced by a standard resistor SR, whose resistance and temperature coefficient is identical to the ink sensor when the system ink concentration is correct. Instead of measuring the absolute resistivity, the monitor measures the system ink resistivity relative to the standard resistor. This relative measurement, expressed as a ratio, is independent of the ink temperature when both standard resistor and system ink are at the same temperature.

A suitable source of alternating-current energy supplied by an alternating- current generator ACG is connected across the bridge, as shown. A conventional resistor R1 and an adjustable resistor R2 comprise two of the legs of the bridge, and the other two legs are composed of the standard resistor SR and the ink sensor assembly IS. The output terminals OP1 and OP2 are connected to the points of the bridge diagonally opposite the input signal. As is usual with bridges of this type, the output voltage at OP1 or OP2 will be zero or negligible when the bridge is balanced, in which condition the products of the impedances of the diagonally opposed bridge arms are equal.

The ink flowing in the system flows through an ink input tube II, shown in Fig. 2, through the standar...