サーモカップル: ಸರಳ ಮತ್ತು ಬಹುಲ ಉಪಯೋಗದ ತಾಪಮಾನ ಸೆನ್ಸರ್
Thermocouple ಯಾವುದು?
A thermocouple is a device that converts temperature differences into an electric voltage, based on the principle of the thermoelectric effect. It is a type of sensor that can measure temperature at a specific point or location. Thermocouples are widely used in various fields, such as industrial, domestic, commercial, and scientific applications, because of their simplicity, durability, low cost, and wide temperature range.
Thermoelectric Effect ಯಾವುದು?
The thermoelectric effect is the phenomenon of generating an electric voltage due to a temperature difference between two different metals or metal alloys. This effect was discovered by German physicist Thomas Seebeck in 1821, who observed that a magnetic field was created around a closed loop of two dissimilar metals when one junction was heated, and the other was cooled.
The thermoelectric effect can be explained by the movement of free electrons in the metals. When one junction is heated, the electrons gain kinetic energy and move faster toward the colder junction. This creates a potential difference between the two junctions, which can be measured by a voltmeter or an ammeter. The magnitude of the voltage depends on the type of metals used and the temperature difference between the junctions.
Thermocouple ಹೇಗೆ ಕಾರ್ಯನಿರ್ವಹಿಸುತ್ತದೆ?
A thermocouple consists of two wires made of different metals or metal alloys, joined together at both ends to form two junctions. One junction called the hot or measuring junction, is placed at the location where the temperature is to be measured. The other junction called the cold or reference junction, is kept at a constant and known temperature, usually at room temperature or in an ice bath.
When there is a temperature difference between the two junctions, an electric voltage is generated across the thermocouple circuit due to the thermoelectric effect. This voltage can be measured by a voltmeter or an ammeter connected to the circuit. By using a calibration table or a formula that relates the voltage to the temperature for a given type of thermocouple, the temperature of the hot junction can be calculated.
The following diagram shows the basic working principle of a thermocouple:
The following video explains how a thermocouple works in more detail:
Thermocouple ವಿಧಗಳು ಏನೆ?
There are many types of thermocouples available, each with different characteristics and applications. The type of thermocouple is determined by the combination of metals or metal alloys used for the wires. The most common types of thermocouples are designated by letters (such as K, J, T, E, etc.) according to international standards.
The following table summarizes some of the main types of thermocouples and their properties:
| Type | Positive Wire | Negative Wire | Color Code | Temperature Range | Sensitivity | Accuracy | Applications |
|---|---|---|---|---|---|---|---|
| K | Nickel-chromium (90% Ni, 10% Cr) | Nickel-aluminum (95% Ni, 2% Al, 2% Mn, 1% Si) | Yellow (+), Red (-), Yellow (overall) | -200°C to +1260°C (-328°F to +2300°F) | 41 µV/°C | ±2.2°C (0.75%) | General purpose, wide range, low cost |
| J | Iron (99.5% Fe) | Constantan (55% Cu, 45% Ni) | White (+), Red (-), Black (overall) | -210°C to +750°C (-346°F to +1400°F) | 50 µV/°C | ±2.2°C (0.75%) | Oxidizing atmospheres, limited range |
| T | Copper (99.9% Cu) | Constantan (55% Cu, 45% Ni) | Blue (+), Red (-), Brown (overall) | -200°C to +350°C (-328°F to +662°F) | 43 µV/°C | ±1°C (0.75%) | Low temperatures, oxidizing atmospheres |
| E | Nickel-chromium (90% Ni, 10% Cr) | Constantan (55% Cu, 45% Ni) | Purple (+), Red (-), Purple |
| E | Nickel-chromium (90% Ni, 10% Cr) | Constantan (55% Cu, 45% Ni) | Purple (+), Red (-), Purple (overall) | -200°C to +870°C (-328°F to +1598°F) | 68 µV/°C | ±1.7°C (0.5%) | High accuracy, moderate range, low cost | | N | Nicrosil (84.1% Ni, 14.4% Cr, 1.4% Si, 0.1% Mg) | Nisil (95.5% Ni, 4.4% Si, 0.1% Mg) | Orange (+), Red (-), Orange (overall) | -200°C to +1300°C (-328°F to +2372°F) | 39 µV/°C | ±2.2°C (0.75%) | General purpose, wide range, stable | | S | Platinum-rhodium (90% Pt, 10% Rh) | Platinum (100% Pt) | Black (+), Red (-), Green (overall) | 0°C to +1600°C (+32°F to +2912°F) | 10 µV/°C | ±1.5°C (0.25%) | High temperature, high accuracy, expensive | | R | Platinum-rhodium (87% Pt, 13% Rh) | Platinum (100% Pt) | Black (+), Red (-), Green (overall) | 0°C to +1600°C (+32°F to +2912°F) | 10 µV/°C | ±1.5°C (0.25%) | High temperature, high accuracy, expensive | | B | Platinum-rhodium (70% Pt, 30% Rh) | Platinum-rhodium (94% Pt, 6% Rh) | Gray (+), Red (-), Gray (overall) | +600°C to +1700°C (+1112°F to +3092°F) | 9 µV/°C | ±0.5% of reading above +600°C (+1112°F) | Very high temperature, low sensitivity |
Thermocouples ಗಳ ಪ್ರಮಾಣಗಳು ಮತ್ತು ದೋಷಗಳು ಎನ್ನುವುದು ಎಂತೆ?
Thermocouples have many advantages and disadvantages compared to other temperature sensors, such as RTDs (Resistance Temperature Detectors), thermistors, or infrared sensors.
Some of the advantages of thermoc
