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Multichannel Reference Junction Compensation Circuit

IP.com Disclosure Number: IPCOM000040077D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Colavito, BC: AUTHOR

Abstract

A described thermal circuit reduces the reference junction temperature difference between any two channels of a multichannel thermocouple reading instrument, thus increasing the overall accuracy of the instrument. This is accomplished without permanently altering the original instrument. The reference junction of a thermocouple circuit is formed when the leads of a thermocouple, other than copper, are attached to the copper input terminals of the thermocouple reading instrument. The accurate determination of the temperature of the reference junction is necessary for the measuring instrument to determine the temperature being monitored by the measurement thermocouple.

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Multichannel Reference Junction Compensation Circuit

A described thermal circuit reduces the reference junction temperature difference between any two channels of a multichannel thermocouple reading instrument, thus increasing the overall accuracy of the instrument. This is accomplished without permanently altering the original instrument. The reference junction of a thermocouple circuit is formed when the leads of a thermocouple, other than copper, are attached to the copper input terminals of the thermocouple reading instrument. The accurate determination of the temperature of the reference junction is necessary for the measuring instrument to determine the temperature being monitored by the measurement thermocouple. Often, multichannel thermocouple measurement instruments will provide one reference junction sensor on a multichannel input/output (I/O) connector and assume all channel terminals are at the same temperature as the point being sensed. A temperature difference (WT) between any channel terminals and the sensor will result in an additional, and sometimes variable, inaccuracy other than those specified by the equipment manufacturer. If matched thermocouples are connected to the + and - terminals of all channels, and measurement junctions were at the same temperature, the difference in the measured temperature of each channel would be due to the temperature difference from the channel terminals to the reference junction sensor. Fig. 1 shows a typical mu...