Glossary

 

B-C
Base Metal Thermocouples

Thermocouples which have conductors made of base element alloys

Bonded Junction Thermocouple construction where wires are attached to the inside of the probe wall at the hot junction, resulting in a quick response time.

Calibration The testing of a thermocouple to determine its emf properties.

Calibration accuracy The "uncertainty" attached to a calibration - no instrument is perfect, the aim is to reduce the inaccuracy to a very low level

CE

A European Rfi/Emi Equipment Specification, Requiring Either Self Certification Or Independent Lab Testing.

Celsius (Centigrade) Temperature scale based on 0° at the ice point and 100° at the boiling point of water.

Chromel® A chromium-nickel alloy used as the positive leg of types K and E thermocouples. Chromel is the tradename of the Hoskins Manufacturing Company.

Class 1 European terminology for the most accurate thermocouple cables defined by emf characteristics. Roughly equivalent to "Special" in N America

Class 2 European terminology for the 2nd most accurate thermocouple cables. Roughly equivalent to "Standard" in N American terminology

Class 3 European terminology for cables calibraed at Zero or below (cryogenic) - very rarely used. Almost always for T Type thermocouples.

Cold Junction Related to thermocouples, also known as the Reference Junction.

Cold Junction Compensation A design feature that compensates for the ambient temperature of the transmitter itself, and the thermocouple effect created by the junction of the thermocouple leads to the transmitter terminal block, either one of which will cause additive errors with the input signal.

Color Code ANSI (or other) established color code for thermocouple wires to ensure connection correctly without secondary thermocouple junctions.

Compensated Connectors

A thermocouple connector that utilizes either actual thermocouple material contacts or compensating alloy contacts. By maintaining uniform circuit properties throughout the connection systems, errors due to mismatched materials are reduced.

Compensating Alloy An alloy that has similar EMF characteristics to an actual thermocouple alloy. It is usually a low-cost alternative for some types of thermocouple alloy extension lead wires. An example would be the use of Alloy #11 as compensating lead wire for platinum thermocouple sensors.

Compensating cable Often it is necessary to arrange the cold junction at some distance from the hot junction for reasons of design, finance or safety. In other cases, the measuring circuit is installed permanently and the actual thermocouple is designed as a measuring insert so that it can easily be replaced. It is then necessary to have a connection cable between the thermocouple and the cold junction with the same thermoelectric properties as the thermocouple itself. This connection is the compensating or extension cable

Connection Head A housing on a sensor assembly that provides a terminal block for electrical connections and allows the attachment of protection tubes and cable or conduit hookups.

Constantan The negative leg of types E, J and T thermocouples. Constantan is 55% copper and 45% nickel. The emf values can be significantly different for this material depending upon with which type of thermocouple alloy it is intended to be matched.

Copper The positive leg of type T thermocouple.

Core Rod Alternate name for the thermocouple or other wire that sits inside the metal sheath & mineral insulation

Cryogenic A term that usually refers to temperatures in the range of -183°C or lower.

CSA Canadian Standards Association. An independent testing laboratory that tests, protects and certifies products and establishes industrial standards.


 
 
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