A thermocouple is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more spots, where a temperature differential is experienced by the different conductors (or semiconductors). It produces a voltage when the temperature of one of the spots differs from the reference temperature at other parts of the circuit.
Thermocouples are a widely used type of temperature sensor for measurement and control, and can also convert a temperature gradient into electricity. Commercial thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation. The main limitation with thermocouples is accuracy; system errors of less than one degree Celsius (°C) can be difficult to achieve.
Any junction of dissimilar metals will produce an electric potential related to temperature. Thermocouples for practical measurement of temperature are junctions of specific alloys which have a predictable and repeatable relationship between temperature and voltage. Different alloys are used for different temperature ranges. Properties such as resistance to corrosion may also be important when choosing a type of thermocouple. Where the measurement point is far from the measuring instrument, the intermediate connection can be made by extension wires which are less costly than the materials used to make the sensor. Thermocouples are usually standardized against a reference temperature of 0 degrees Celsius; practical instruments use electronic methods of cold-junction compensation to adjust for varying temperature at the instrument terminals. Electronic instruments can also compensate for the varying characteristics of the thermocouple, and so improve the precision and accuracy of measurements.
Thermocouples are widely used in science and industry; applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes. Thermocouples are also used in homes, offices and businesses as the temperature sensors in thermostats, and also as flame sensors in safety devices for gas-powered major appliances.”
Business and industry are spending considerable time and money improving the efficiency of their manufacturing processes. Reducing scrap, increasing throughput, and improving product quality are today’s benchmarks for success.
Temperature is the most frequently measured process variable. To be competitive, industry needs to control and monitor process temperatures to the highest degree of accuracy.
In response to this need, a super accurate thermocouple wire which surpasses the performance of ASTM/ANSI special limits initial accuracy tolerance. The accuracy of thermocouple wire is expressed as deviation from the published NIST voltage versus temperature relationship for each type of wire.
This chart shows the accuracy advantage of ACCUTHERM™ thermocouple wire over the initial calibration tolerances for standard limits and special limits.
The initial calibration tolerance for ACCUTHERM™ is approximately four times that of standard limits thermocouple wire and double that of special limits thermocouple wire. Whether your process is Heat Treating or Autoclave Validation; Performance Testing or Research and Development; Aerospace or Metals, ACCUTHERM™ will give you the temperature accuracy readings you need to remain competitive. When high accuracy temperature measurements are critical to your process, ACCUTHERM™ is the answer. Initial Calibration Tolerances per ASTM E230 and ANSI MC96.1 Thermocouple Type Standard Limits Tolerance* Special Limits Tolerance* ACCUTHERM™ Tolerance.
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