resistance secondary standard
Date: circa 1918
Inventory Number: 1997-1-0226a
Classification: Resistance Standard
Subject:
Maker: Leeds & Northrup Company ? (1903 - 1995)
Cultural Region:
Place of Origin:
Dimensions:
8.5 x 9.3 x 6 cm (3 3/8 x 3 11/16 x 2 3/8 in.)
Material:
Description:
The resistance consists of a small hard-rubber block on which a cylinder has been set. Inside the cylinder is a coil linked to the two protruding metallic side leads and the two binding posts.
Signedunsigned
FunctionA standard resistance 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. This secondary standard, which was simply plugged in a circuit, was probably added to the circuit to provide more precision readings.
According to this website, "Two current and two potential leads make these coils useful for measuring currents via the four-terminal method. The spacing of the projecting lugs allowed them to be plugged into the 1-meter student slide wire bridge... The resistance values are good to one part in 1000."
According to this website, "Two current and two potential leads make these coils useful for measuring currents via the four-terminal method. The spacing of the projecting lugs allowed them to be plugged into the 1-meter student slide wire bridge... The resistance values are good to one part in 1000."
Curatorial RemarksSet of 5 such devices - serial number 29927 missing.
