Browse Prior Art Database

Multifunction Liquid Level and Leak Monitor

IP.com Disclosure Number: IPCOM000074436D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Ciminera, JR: AUTHOR

Abstract

The combination of a single thermistor sensor and a time domain circuit or detector can be arranged to indicate a low-liquid level condition, to initiate the transfer of liquid from an auxiliary to a main reservoir, to indicate the return of the liquid to a normal level, to warn of possible liquid leaks in the system and to inferentially indicate that an auxiliary liquid tank is empty.

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Multifunction Liquid Level and Leak Monitor

The combination of a single thermistor sensor and a time domain circuit or detector can be arranged to indicate a low-liquid level condition, to initiate the transfer of liquid from an auxiliary to a main reservoir, to indicate the return of the liquid to a normal level, to warn of possible liquid leaks in the system and to inferentially indicate that an auxiliary liquid tank is empty.

The low-liquid level is indicated by a thermistor 10 which is mounted at a predetermined level in a main reservoir. The thermistor s self-heated so as to sense the absence of surrounding liquid by increasing in temperature rapidly with the result of a decrease in resistance. When immersed, the thermistor 10 has a low temperature and a corresponding high resistance but once uncovered by the liquid, the temperature increases rapidly with a resultant decrease in resistance (negative coefficient). The change in temperature is detected by a voltage divider network and a semiconductor level-sense detector 12 which drives a 24 volt relay K17. One set of contacts of this relay is used to operate a low-level indicating light. The fill phase and the return to normal level of the reservoir is indicated after relay K17 has been picked. This relay initiates a time-delay relay TD1 which controls a solenoid 14 on the auxiliary tank. The quantity of liquid drained from the auxiliary tank to the main reservoir is a function of the time of time-delay relay TD1. Thus, this relay is adjusted to allow the required amount of liquid to drain from the auxiliary tank into the main reservoir. It will be appreciated that this delay function eliminates the frequent demand-fill cycle which would occur if the solenoid 14 responded directly to the level sensor ID. The rel...