Skip to main content
  • Utility Menu
  • Search
Harvard Logo
HARVARD.EDU

Collections Menu
  • Waywiser
  • People
  • Bibliography
  • Exhibitions
  • Thesaurus
  • My Object Lists
  • About
  • Sign in
Advanced Search
  • Home
  • Objects
  • resistance standard (0.001 Ohm)
  • Images (3)

resistance standard (0.001 Ohm)

  • Images (3)

resistance standard (0.001 Ohm)

Date: 1880-1910
Inventory Number: 0302a
Classification: Resistance Standard
Subject:
electricity, electrical engineering,
Maker: Otto Wolff (fl. 1870 - 1920)
User: Department of Physics, Harvard University (founded 1884)
Owner: Harvard Engineering School (1918 - 1951)
Cultural Region:
United States, Germany,
Place of Origin:
Berlin,
City of Use:
Cambridge,
Dimensions:
15.6 cm (6 1/8 in.)
Material:
metal, hard rubber, manganin,
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.



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;

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."
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.
ProvenanceFrom the Harvard Engineering School, 11/56.

Relationships

See also/See also
View all

Choose Collection

Create new collection

facebook iconTwitter Logo

_______________________________
Join Our Mailing List I Contact
_______________________________
The Collection of Historical Scientific Instruments
Science Center, Room 371 • 1 Oxford Street
Cambridge, MA 02138 •chsi@fas.harvard.edu
p. 617-495-2779 •
f. 617-496-5794
_______________________________
The CHSI is one of the

HMSC Logo

Exhibition Hours

The Putnam Gallery
(Science Center 136):
Monday through Friday, 11a.m. to 4p.m.


The Special Exhibitions Gallery
(Science Center 251):
Monday through Friday, 9a.m. to 5p.m.


The Foyer Gallery
Closed for Installation.

All galleries are closed on University Holidays.

Admission is free of charge.
Children must be escorted by an adult.

Admin Login
OpenScholar
Copyright © 2017 The President and Fellows of Harvard College | Privacy | Accessibility | Report Copyright Infringement

Choose Collection

Create new collection