resistance standard (20 ohms)
Date1935-1936
Inventory Number1997-1-0227c
ClassificationResistance
Subject
Maker
Leeds & Northrup Company
1903 - 1995
Cultural Region
Place of Origin
Dimensions17.9 × 10 × 4.6 cm (7 1/16 × 3 15/16 × 1 13/16 in.)
box: 11.5 x 49.9 x 19.9 cm (4 1/2 x 19 5/8 x 7 13/16 in.)
box: 11.5 x 49.9 x 19.9 cm (4 1/2 x 19 5/8 x 7 13/16 in.)
Material
Accessoriesstorage box
DescriptionCoil of manganin wound on a tube supported in a perforated nickel-plated case. Two heavy terminals, with two adjustment knobs on each, are protruding 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 20 Ohms and is calibrated for 20°C.
The top is inscribed, "20 Ohms / LEEDS & NORTHRUP / PHILADELPHIA / 206993 / MADE IN U.S.A."
This inventory number contains two families of five instruments each -- all are Leeds & Northrup Resistance Standards, National Bureau of Standards type, but they are two different designs from two different periods: five (a-e) are from 1935-36 and the other five (f-j) are from 1926-29.
All of the later instruments (a-3), and 3 of the 5 earlier instruments (f-j), have their original makers' tags, giving dates of baking and sealing, serial number, catalog number, order number, etc. 4 of the 5 earlier instruments (f-j) are tagged with a hand-painted green triangle, as found on some of the 1997-1-0225 family of resistance standards. Some of these leaked oil at some point in the past. The entire family is stored in an open wood case with 24 sections.
The resistance is 20 Ohms and is calibrated for 20°C.
The top is inscribed, "20 Ohms / LEEDS & NORTHRUP / PHILADELPHIA / 206993 / MADE IN U.S.A."
This inventory number contains two families of five instruments each -- all are Leeds & Northrup Resistance Standards, National Bureau of Standards type, but they are two different designs from two different periods: five (a-e) are from 1935-36 and the other five (f-j) are from 1926-29.
All of the later instruments (a-3), and 3 of the 5 earlier instruments (f-j), have their original makers' tags, giving dates of baking and sealing, serial number, catalog number, order number, etc. 4 of the 5 earlier instruments (f-j) are tagged with a hand-painted green triangle, as found on some of the 1997-1-0225 family of resistance standards. Some of these leaked oil at some point in the past. The entire family is stored in an open wood case with 24 sections.
Signedstamped on top: Leeds & Northrup Co. / Philadelphia
Inscribedinscribed on top: 20 Ohms / LEEDS & NORTHRUP / PHILADELPHIA / 206993 / MADE IN U.S.A.
Curatorial RemarksNational Bureau of Standards Type.
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.
Leeds & Northrup Company
Date: 1935-1936
Accessories: storage box
Object number: 1997-1-0227b
Leeds & Northrup Company
Date: 1926-1929
Accessories: storage box
Object number: 1997-1-0227i
Leeds & Northrup Company
Date: 1935-1936
Accessories: storage box
Object number: 1997-1-0227a
Leeds & Northrup Company
Date: 1935-1936
Accessories: storage box
Object number: 1997-1-0227e
Leeds & Northrup Company
Date: 1935-1936
Accessories: storage box
Object number: 1997-1-0227d
Leeds & Northrup Company
Date: 1926-1929
Accessories: storage box
Object number: 1997-1-0227h
Leeds & Northrup Company
Date: 1926-1929
Accessories: storage box
Object number: 1997-1-0227f
Leeds & Northrup Company
Date: 1926-1929
Accessories: storage box
Object number: 1997-1-0227g
Leeds & Northrup Company
Date: 1926
Accessories: storage box
Object number: 1997-1-0227j
Leeds & Northrup Company
Date: early 20th Century
Object number: 1997-1-1221
