Browse Prior Art Database

Continuous Temperature Monitoring System

IP.com Disclosure Number: IPCOM000076279D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Pulyer, RC: AUTHOR [+2]

Abstract

This temperature monitoring system is employed in sensing resistive changes in a temperature sensing element.

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 53% of the total text.

Page 1 of 2

Continuous Temperature Monitoring System

This temperature monitoring system is employed in sensing resistive changes in a temperature sensing element.

A reference voltage is produced by resistors R1 and R2 and zenor diode D1. This reference voltage is fed into a differential amplifier along with the sensing element. The gain of the operational amplifier is controlled by resistor R3. The output of the operational amplifier (point A) is fed to two Schmitt trigger circuits. The operation of each Schmitt trigger circuit is as follows: normally, transistor Q1 is off and Q2 is on, therefore, biasing the gates of silicon-controlled rectifiers (SCR's) D2 and D3 off. When the temperature of the sensing element increases, its resistance decreases. This causes the output voltage of operational amplifier (point A) to increase. this voltage is fed to two Schmitt trigger circuits through R4 and R5. This voltage increases with the temperature until the firing point of each Schmitt trigger is reached. When the Schmitt trigger fires, it causes the voltage applied to the gates of SCR's to pass through their "gate threshold voltage", causing the SCR's to conduct. When SCR's D2 and D3 conduct, D3 turns on an indicator lamp LP2 to inform the operator that the predetermined trip point has been reached. SCR's D2 will turn on the customers' external load.

The trip point of each Schmitt trigger is adjusted by resistors R4 and R5; therefore, circuit numbers 1 and 2 can be set for different trip p...