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Integrated Circuit Module Liquid Level Detection

IP.com Disclosure Number: IPCOM000081411D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Robbins, GJ: AUTHOR

Abstract

This liquid level sensing technique relies on the self-heating effect of a thermistor, to detect the absence of coolant liquid at a certain level in a multichip integrated circuit module. A thermistor and resistor Rx form one side of a bridge circuit. The remaining portion of the bridge circuit is contained on a logic masterslice chip, along with the bridge-sense amplifier and send component (off-chip driver).

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Integrated Circuit Module Liquid Level Detection

This liquid level sensing technique relies on the self-heating effect of a thermistor, to detect the absence of coolant liquid at a certain level in a multichip integrated circuit module. A thermistor and resistor Rx form one side of a bridge circuit. The remaining portion of the bridge circuit is contained on a logic masterslice chip, along with the bridge-sense amplifier and send component (off- chip driver).

The mesterslice (MS) mey perform normal random-logic functions, except for the cells which are utilized for each level detector. There is no overhead on other MS chips on the module, as these chips have their "liquid level cells" wired as regular logic gate functions or send components.

The circuit shown in the drawing has several desirable features:
1) Constructed out of standard T2L logic gate circuit elements.
2) Differential inputs are less susceptible to power supply

noise and variations.
3) Circuit is fail-safe for thermistor open or Rx short.

The Rx resistor is dependent on the thermal characteristics of the thermistor selected and may be in the 50-150 ohm resistance range. This component is discrete on the module which allows for trimming of the circuit for various uncertainties of the design, and allows tight tolerance on this resistance value resulting in a larger noise margin.

The reference leg of the bridge is a 2:1 voltage divider which is comprised of paralleled combinations of dissimilar value...