resistance standard (100.0 Ohm)
Date: 1880-1910
Inventory Number: 0302i
Classification: Resistance Standard
Subject:
Maker: Otto Wolff (fl. 1870 - 1920)
Cultural Region:
Place of Origin:
Dimensions:
16.4 x 16.4 x 8.3 cm (6 7/16 x 6 7/16 x 3 1/4 in.)
Material:
Description:
Coil of manganin wound on a tube supported in a perforated nickel-plated case. Two heavy terminals are protruding from the hard rubber top for suspension in mercury to a standard bridge set in an oil bath.
The resistance is 100 Ohms and is calibrated for 20°C.
The resistance is 100 Ohms and is calibrated for 20°C.
Signedstamped on top: O. Wolff Berlin
Inscribedon top: manganin
on side: H.U. / 111-A
on side: H.U. / 111-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."
Curatorial RemarksWas first incorrectly catalogued as 1997-1-0225o.
Though they are probably from a different origin, this bridge could have been used with the resistance standards 0302b, 0302d, 0302f, 0320g, 0302h, the resistance bridge 0301, and the oil tray 0303.
Though they are probably from a different origin, this bridge could have been used with the resistance standards 0302b, 0302d, 0302f, 0320g, 0302h, the resistance bridge 0301, and the oil tray 0303.
ProvenanceFrom the School of Engineering, Harvard University.
