| 摘要 |
A method of making an elongated electrical heating element having a resistance wire with a helical portion extending between two lead pins surrounded by compacted insulating powder in an outer casing. The lead pins are attached to a tightly coiled resistance wire by screwing threaded portions at the inner ends of the lead pins into coiled portions at the outer ends of the resistance wire. The lead pins are pulled further apart to stretch the coiled resistance wire to form the helical portion of the resistance wire and then attached to a resistance meter. One of the lead pins is then rotated relative to the other lead pin to adjust the effective electrical resistance of the heating element to an accurate and uniform valve. The resistance wire and lead pins are mounted in an outer casing which further stretches the helical portion to a predetermined length. The outer casing is then filled with insulating powder in a conventional vibrating filling machine. Finally, the casing is compressed to compact the insulating powder around the heating element.
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