thermocouple

(1) After overlapping the platinum-rhodium alloy wires, they are welded using an electric soldering iron along with tin and rosin. (Unverified method) (II) Welding using the following method is both convenient and feasible, as well as cost-effective. The method is described as follows: I. Preparation work 1. Use a beaker of 50 oral capacity to collect 50 oral worth of saturated brine for salt production; place this brine in the beaker. Utilize a 22V AC power supply with normal lighting, and use a voltage regulator to reduce the voltage to around 12V. Insert a copper sheet attached to a alligator clip into the beaker – this serves as one electrode ； The other level is the platinum-rhodium-platinum wire that requires welding. Temporarily disconnect the power supply (220V). 2. Twist the two ends of the platinum-rhodium-platinum wire to be welded together; the twisting length is generally 1–2 millimeters, with the ideal result being a small spherical shape after welding. (The author usually keeps it at 1.5 millimeters.) The distance between the rhodium-coated platinum wire and the wire after the twisting point is 5 millimeters; after burning away the paper using cigarette foil, the wire is folded several times to wrap around the rhodium-platinum wire, and then the foil is held in place with fish clips. II. Welding 1. Connect the 22V power supply. 2. Put on sunglasses and lined gloves. 3. Use glue to secure the carp clip, then slowly insert the junction of the platinum-rhodium to platinum wire that needs to be welded into the brine; the insertion depth should be just enough so that the entire length of the joint goes in. At this point, a dark red light appears in the brine along with a slight explosion sound; when the red light turns into green, a white sphere can be seen within the green light, indicating that the welding has been successful. 4. Examine the welded area with a magnifying glass to check the quality of the weld and whether there are any cracks resulting from twisting around the joint. Through numerous practical experiences, I have found that two points need to be noted: 1. The main factors affecting successful welding are that there should be no outward stress at the joint; if such stress is present, the weld spot will bulge outward during formation, making it difficult to create a round weld spot. 2. During welding, when the red light changes to green light, if one is in a hurry and raises the component out of the brine too early, before a round solder joint has formed, it can be inserted back into the brine until a small spherical shape appears on the joint. Below are the tools and parameters commonly used during welding, for those who wish to weld as reference. III. One pair of utility glue pliers, one pair of needle-nose pliers (for twisting joints), two fish clips, one 50-ml beaker, one piece of red copper sheet measuring 20 mm × 40 mm, one voltage regulator, one piece of cigarette foil (with one layer burned off), and a pair of ordinary sunglasses.