resistance standard (0.001 Ohm)
Date: 1880-1910
Inventory Number: 0302a
Classification: Resistance Standard
Subject:
Maker: Otto Wolff (fl. 1870 - 1920)
User: Department of Physics, Harvard University (founded 1884)
Owner: Harvard Engineering School (1918 - 1951)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
15.6 cm (6 1/8 in.)
Material:
Description:
Coil of manganin wound on a tube supported in a perforated nickel-plated case. Two heavy terminals, two binding posts and one center knob protrude from the hard rubber top for suspension in mercury to a standard bridge set in an oil bath. There is a thermometer inside the container as well.
The resistance is 0.001 Ohms and is calibrated for 20°C.
The resistance is 0.001 Ohms and is calibrated for 20°C.
Signedtop of the cylinder inscribed: O. Wolff Berlin
Inscribedtop of the cylinder inscribed: 0.001 Ohms / bei 20°C / Manganin / O. Wolff Berlin / 4370;
side of cylinder is inscribed: H.U. 120-A;
side of cylinder is inscribed: H.U. 120-A;
FunctionA resistance standard is not to measure the resistance of an electric conductor but rather to compare such a conductor to a temperature-fixed resistance. In other words, such a device is used to determine the value of an unknown current. To do so, a current in the conductor would pass through mercury (for the older type of standard resistance), into which the two leads from the resistor dip. The manganin wire in this instrument was baked before being dipped into paraffin so that all moisture is removed and to improve the insulation over the wire.
This one was used with other similar resistances of different values and a bridge to connect several of them together.
From Card:
"Ref. An adaptation of the standard use in 1865 (See report Standards Committee - british 1873, p136.pl.4). At the time wire of 2/3 silver and 1/3 platinum were used. Coil surrounded by wire and suspended in water bath. (See also J.E.H. Gordon. Elec & Mag [London 1883] p.267. p321, pl.24). This variety has replaced the earlier form."
This one was used with other similar resistances of different values and a bridge to connect several of them together.
From Card:
"Ref. An adaptation of the standard use in 1865 (See report Standards Committee - british 1873, p136.pl.4). At the time wire of 2/3 silver and 1/3 platinum were used. Coil surrounded by wire and suspended in water bath. (See also J.E.H. Gordon. Elec & Mag [London 1883] p.267. p321, pl.24). This variety has replaced the earlier form."
Historical AttributesThere is a gray (or faded blue) triangle painted on side, indicating it was used as a demonstration instrument in the physics department at Harvard.
Curatorial RemarksThis object is listed on the CHSI 8" x 10" cards but was not found in 1997 during inventorying, nor has it surfaced during shelf reading 2007-2008.
Information from CHSI 8" x 10" card: O. Wolff, 4370, H.U. 120-A, Engineering School to CHSI 11/56.
Information from CHSI 8" x 10" card: O. Wolff, 4370, H.U. 120-A, Engineering School to CHSI 11/56.
ProvenanceFrom the Harvard Engineering School, 11/56.
