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Carbon Film Resistors: Methane Cracked on Ceramic Rods, Helixed and Varnished (Bell Labs 1951)
Ceramic rods tumble in a hot, gas-tight rotating furnace while methane cracks on them and leaves a thin, hard film of carbon. The coated rods get conducting ends, a helix ground through the film to bring them near their value, a light rub to the exact value, and a coat of baking varnish.
Result: carbon film resistors adjusted to as close as ±0.5 %. The helix alone can raise a rod's resistance by any factor from about 10 to about 8000.
Source: Grisdale, Pfister and van Roosbroeck, Pyrolytic Film Resistors, Bell System Technical Journal 30 (1951). Unknown: the ceramic of the rods, the end caps and leads, and which baking varnish; the paper does not give them. Picture: Wikimedia Commons.
고급
2 days
안내
1
1
Load the furnace
Load the furnace
Load cylindrical ceramic rods into the gas-tight refractory core of a rotating (or rocking) batch furnace, with silica sand to support the rods and keep them from damage as they tumble. Unknown: which ceramic.
이 단계의 재료:
저항기 절연 코어1 batch필요한 도구:
회전식 배치로
규사2
2
Heat under nitrogen
Heat under nitrogen
Turn the core and bring it to temperature, usually about 975 to 1300 °C, flushing it with nitrogen before any hydrocarbon goes in.
필요한 도구:
회전식 배치로
질소3
3
Crack the methane
Crack the methane
When the temperature is steady, let in the coating gas and keep it flowing for the time needed. The film grows at a steady rate: at 1000 °C and 30 % methane the paper runs from 0.2 to 10 hours. Longer gives a thicker film of lower resistance; temperature sets the rate more than anything else, and more methane deposits faster.
이 단계의 재료:
메탄1 flow필요한 도구:
회전식 배치로4
4
Cool under nitrogen
Cool under nitrogen
Shut off the methane and let the core cool while oxygen-free nitrogen keeps flowing. The films come out clean, even and firmly stuck.
필요한 도구:
회전식 배치로질소5
5
Terminate the ends
Terminate the ends
Paint the ends of each coated rod with a water suspension of colloidal graphite (Aquadag), then burnish and bake it; this suits all but low-value resistors. Fit the end caps with their leads. Unknown: the caps and leads, which the paper does not describe. Ours: an agate burnisher and an oven.
이 단계의 재료:
콜로이드 흑연1 as required
리드선 달린 저항기 캡2 per resistor필요한 도구:
마노 광내기 도구
오븐6
6
Grind the helix
Grind the helix
Grind a helical groove through the film with a water-cooled, metal-bonded diamond wheel, the blank floating against the wheel so the groove stays even. Pick the pitch to land slightly below the wanted value (330 Ω, 10 kΩ or any other). The groove must be smooth: cracks into the carbon ribbon bring noise and drift.
필요한 도구:
저항기 나선 절삭기7
7
Rub to value and varnish
Rub to value and varnish
Turn the resistor while measuring it continuously, and rub its whole surface lightly with a cotton pad wet with an organic solvent until it reaches its value. Leave it just below tolerance, then give it one or more coats of baking varnish, which raises the resistance by generally less than 1 %. Unknown: which varnish and its baking. Ours: acetone as the solvent, a Wheatstone bridge to measure.
이 단계의 재료:
베이킹 바니시1 as required필요한 도구:
휘트스톤 브리지
탈지면
아세톤오븐재료
5- 1 batch플레이스홀더
- 1 flow플레이스홀더
- 1 as required플레이스홀더
- 2 per resistor플레이스홀더
- 1 as required플레이스홀더
관련 블루프린트
이 블루프린트들은 지식을 공유합니다 — 기술, 재료 또는 원리
CC0 퍼블릭 도메인
이 블루프린트는 CC0로 공개되었습니다. 어떤 목적으로든 자유롭게 복사, 수정, 배포 및 사용할 수 있습니다.
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