【Weekly Question 20090907】Thermocouple Identification
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There is a thermocouple with a very hard material; please use a simple method to determine its calibration number and the positive and negative poles, and select one from the red/blue insulated wires and the red/yellow insulated compensation wires. Note: For multiple accounts sharing the same IP, only the first response counting as participation is valid! Copying the answer is invalid!
It’s very hard; it’s certain that it’s not platinum-rhodium-platinum.
Determine the degree number based on color, and assess its magnetism by checking the positive and negative poles.
K-type thermocouples made of nickel-amercury and nickel-silicon are relatively hard and widely used; the nickel-amercury variant is dark green in color and serves as the positive electrode； Nickel-silicon with a gray-black color serves as the negative pole; the compensation wire is a copper-constantan wire with red or blue insulation (red for positive, blue for negative).
Given its very hard texture, it definitely isn’t platinum-rhodium–platinum. It could be nickel-chromium – nickel-silicon or nickel-chromium – constantan; the surface of the nickel-chromium cathode is black-brown in color, the nickel-silicon anode is green-black, while the constantan anode has a slightly whiter color ； A magnet can also be brought near the negative pole; if it is magnetic, it is nickel silicon, and if it is not magnetic, it is constantan. Nickel-chromium – nickel-silicon with red-blue insulated compensation wire (copper – constantan); nickel-chromium – constantan with reddish-brown insulated compensation wire (nickel-chromium – constantan).
It’s very hard; it definitely isn’t platinum-rhodium-platinum. To determine whether it is nickel-chromium-nickel-aluminum or nickel-chromium-copper, the positive and negative poles can be identified first. The cathode nickel-chromium surface has a brownish-green layer, making it easy to identify. Then bring a magnet close to its negative pole; if it is attracted, it is nickel-aluminum, otherwise it is copper. Nickel-chromium nickel-aluminum thermocouples should be used with compensation wires with red or blue insulation (copper, constantan), while nickel-chromium constantan thermocouples should be used with compensation wires with red or yellow insulation (nickel-chromium, constantan).