협업
예술
뷰티 및 웰니스
공예
문화 및 역사
엔터테인먼트
환경
음식 및 음료
역공학
과학
스포츠
기술
웨어러블
Electronic Analytical Balance: a Coil Current in Place of Weights (Akers et al., 1977)
The equal-arm balance with its weights replaced by electricity. The pan sits on a coil in the gap of a permanent magnet. A load pushes it down; capacitor rings sense the smallest movement, and a servo drives just enough current through the coil to lift it back to its rest position. That current is the weight.
Result: a balance that reads the weight in grams or ounces on a digital display, with no weights to handle, and tare by its circuit.
Source: C. B. Akers and others (Arbor Laboratories), US Patent 4,034,819 (1977). Unknown: the resolution, capacity, magnet type, materials and sizes; the circuits are given as blocks only. Picture: patent drawing.
고급
2 weeks
안내
1
1
Build the magnet circuit
Build the magnet circuit
Stack permanent magnets into a column with a soft iron core. Enclose them in an annular outer housing with end caps, shaped so the field crosses a narrow annular air gap at a constriction. Keep the whole structure symmetrical about its vertical axis. Mount it on a support plate fixed to an upright, such as a housing panel on a base. Not given: the magnet type, materials and sizes.
이 단계의 재료:
작은 자석1 column
철 환봉1 soft iron core
알 수 없는 금속1 housing and end caps
알 수 없는 재료1 support plate, panel, base필요한 도구:
드라이버 세트
알 수 없는 치수2
2
Hang the coil in the gap
Hang the coil in the gap
Wind the coil tightly round the middle of a light bobbin that surrounds the core, the coil sitting in the air gap. Tabs at both ends of the bobbin pass out through holes in the end caps to suspension frames. Hang the frames from thin springy cantilevers fixed to the upright, so the bobbin can only move a short way straight up and down. Keep the bobbin and its suspension as light as possible. Put the weighing pan on top. Ours: enamelled wire.
이 단계의 재료:
에나멜 피복 구리선1 coil알 수 없는 재료1 bobbin, frames, cantilevers
계량 접시1 개필요한 도구:
알 수 없는 치수3
3
Fit the capacitor rings
Fit the capacitor rings
Mount four capacitor rings inside the outer housing, two above and two below the air gap, facing matching rings on the bobbin. Cross-connect them so a tilt of the bobbin cancels out and only up-and-down movement shows. Connect them to a signal generator: as the bobbin moves, one set's capacitance rises and the other's falls, and the difference becomes the control voltage.
이 단계의 재료:
알 수 없는 금속1 rings
집적 회로(IC)1 sensing circuit
배선용 전선1 개
땜납 선1 a little필요한 도구:
인두4
4
Close the servo loop and read the current
Close the servo loop and read the current
Feed the control voltage to a d.c. servo that drives current through the coil, through a flexible lead, until the bobbin is back at its rest position. Pass that current through a large stable resistor, a thermal resistor that corrects for temperature and a calibration potentiometer: the voltage across them stands for the weight. A separate circuit (comparators, saw-tooth generator, oscillator and counter) turns it into a count read out as grams or ounces. Tare is ordinary circuit logic. Ours: a segment LCD; check with calibration weights.
이 단계의 재료:
집적 회로(IC)1 servo and counting circuits
전기 저항2 stable resistor, thermal resistor
가변저항기1 calibration
세그먼트 액정 패널1 display땜납 선1 a little필요한 도구:
인두
교정용 분동 세트재료
12- 1 column플레이스홀더
- 1 soft iron core플레이스홀더
- 1 rings플레이스홀더
- 1 bobbin, frames, cantilevers플레이스홀더
- 1 coil플레이스홀더
- 1 개플레이스홀더
- 1 servo and counting circuits플레이스홀더
- 1 개플레이스홀더
- 2 a little플레이스홀더
- 2 stable resistor, thermal resistor플레이스홀더
- 플레이스홀더
- 1 display플레이스홀더
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