resistance standard (0.1 Ohm)
Date1880-1910
Inventory Number0302c
ClassificationResistance Standard
Subject
Maker
Otto Wolff
fl. 1870 - 1920
User
Harvard Engineering School
1918 - 1951
Cultural Region
Place of Origin
Place of Use
Dimensions16.5 × 8.5 × 18.7 cm (6 1/2 × 3 3/8 × 7 3/8 in.)
Material
DescriptionCoil of manganin wound on a tube supported in a perforated nickel-plated case. Two heavy terminals 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 0.1 Ohms and is calibrated for 20°C.
The top of the cylinder is inscribed, "0.1 Ohms / bei 20°C / Manganin / O. Wolff Berlin / 4472"; the side of the cylinder is inscribed, "H.U. 116-A"
The resistance is 0.1 Ohms and is calibrated for 20°C.
The top of the cylinder is inscribed, "0.1 Ohms / bei 20°C / Manganin / O. Wolff Berlin / 4472"; the side of the cylinder is inscribed, "H.U. 116-A"
Signedinscribed on top: O.Wolff
Inscribedtop of the cylinder inscribed: 0.1 Ohms / bei 20°C / Manganin / O. Wolff Berlin / 4472;
side of the cylinder inscribed: H.U. 119-A
Curatorial RemarksThis Resistance Standard not found during 1997 inventory project nor during 2007-2008 shelf reading project. See CHSI 8" x 10" inventory card 0302 for more information.
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."
ProvenanceFrom the Harvard Engineering School removed to CHSI 11/56.
