Gerber GraphAnalogue
Date: circa 1950
Inventory Number: 2003-1-0234
Classification: Computing Rule
Dimensions:instrument: 1.4 × 13 × 36 cm (9/16 × 5 1/8 × 14 3/16 in.)
case: 3.3 × 15.5 × 39.3 cm (1 5/16 × 6 1/8 × 15 1/2 in.)
Accessories: instruction booklet (with instrument); light brown leatherette case with brown velvet lining; six sheets of graph paper
DescriptionBlack aluminum rectangular base with grooves near its top and bottom long edges. A rectangular aluminum plate is screwed to the center of the base. A semi-cylindrical piece of clear plastic runs along the length of the top edge of the base, and is attached to silver aluminum end caps at either end of the base.
A silver aluminum runner moves to left and right along the base's two grooves. Screwed to the left side of the runner is a clear plastic rectangle with a vertical indicating line.
Two springs are attached to the left end cap and left side of the runner and sit beneath the semi-cylindrical plastic pice. The top spring is triangular, with every fifth coil colored. The bottom spring is circular, and has white labels on five of its coils: 0, 2, 4, 6, 8, 10. The springs stretch and contract together when the runner is moved to right and left.
Eighteen scales are printed on the rectangular plate screwed to the top of the base. The top scale, "R_I", is an inverted logarithmic scale with values descending from 100 to 10. Below this is an inverted logarithmic scale, "R_F", with values descending from 1200 to 120. A third inverted logarithmic scale, "R_C", is printed third from the top, and has values descending from 39 to 4.
Below the "R_C" scale is a scale "I", with values ranging from 1 to 10. Fifth from the top is an "F" scale carrying values from 0.1 to 0.8. Below this is a "C_M" scale with values ranging from 3 to 25, then two "T" scales. The top "T" scale has values ranging from 6 to 45; the bottom T scale has values ranging from 45 to 84.
Ninth from the top is an "S_1 C_0" scale, marked with two sets of values. The first set ascends from 6 to 90; the second set descends from 84 to 0. Below this is a "D" scale with values ranging from 10 to 90.
Below the "D" scale are two "( )^2" scales; the top scale has values ranging from 1 to 3.1, the bottom, from 3.2 to 10. Below these are, first, a "( )^(1/2)" scale, with values ranging from 1 to 100, then, a "( )^(1/3)" scale, carrying values from 1 to 1000.
Fifteenth from the top is an "L_10" scale, with values ranging from 1.3 to 10. Below this are two "L_e" scales. The top scale has values ranging from 1.11 to 2.7; the bottom scale has values ranging from 3 to 20,000. The bottom scale is a "P" scale, with values ascending from 0.2 to 99.99.
The instrument is accompanied by six sheets pink of graph paper. Each sheet has a ragged left edge, near which is printed: "SPRING LENGTH = 1.000 INCHES".
The instrument, paper, and instruction manual are stored in a light brown leatherette case with brown velvet lining.