Chapter 4, An Inexpensive Vertical Seismometer for Classroom Demonstrations: Parts List

Developed for the Mid America Earthquake Center Workshop

at Georgia Tech, June 22-25, 1998

Parts List

No.Part #DescriptionApproximate Cost

Note:One 1" x 6" x 24"oak board builds base and all blocks5.00

__) 1Spring Mounting Bracket wood block 1 3/16 x 4"

The holes for the mounting bolts are drilled first and then used as guides to drill a set of holes in the base for adjustment of the spring length.

__) 1 Eye bolt, 2" #8 (3/16") x 24 with nut2@$0.780.39

__) 2Machine Screws, #8 x 32 x 2 1/2" 2@$0.780.39

__) 2Machine nuts #8 x or $0.10 each0.20

__) 1Displacement Sensor Mounting Bracket a wood block 1 5/8 x 3 

__) 2Wood Screws #6 x 1 1/4" with counter sunk heads0.40

__) 1 Photo sensitive resistor (Cadmium-sulfide PV cell-Radio Shack 276-1657)0.35

__) 1Travel Limit Block 5 x 1 

__) 2Wood Screws #6 x 1 1/4" with counter sunk heads0.20

__) 2Machine Screws, #6 x 32 x 1"

__) 2Machine nuts #6 x 32 ($3.39/100)@0.050.10

__) 2Travel limit arms, Aluminum bar stock 1/8" x " x 2"0.1

__) 1Base Board (6" x 1" x 18"), see picture of parts for layout of holes

__) 1U-bolt, 3 " wide x 6" high 3/8" diameter, 16 th/ w/flat plate2.99

__) 2Extra nuts for U-bolt, 3/8" x 160.20

__) 1Threaded insert, 3/8" insert holder for wood base plate0.75

__) 1Bolt, 3/8" x 2" with locking nut0.45

__) 116  of Aluminum Channel Trim "($8.99/8ft) or $0.57/61.71

The lever bar needs to be pre-drilled for mounting of bolts etc.

__) 2hinge assembly 6" of Aluminum Channel Trim "1.14

The top hinge has spaces cut out for the U-bolt to pass through, the lower hinge is fitted with holes in the center to set the placement of the lever arm.

__) 1Clamping bar, Aluminum bar stock 1/8" x " x 6"($5.49/8' $0.055/)0.33

__) 1Machine Screw #6 x 32 x 1" Connect hinge assembly to bar

__) 6Machine screws #6 x 32 x 1/4($1.99/100)0.12

__) 2Machine screw, #6 x 32 x 3/4($1.97/100)@0.050.04

__) 9Nuts#6 x 32 ($1.24/100)0.10

__) 8flat washers, #6($2.99/100)0.24

__) 4Hinge elements, 1/4" x 1" (made from soft drink can)

__) 1Screen Door Spring (typically 24") cut to 4"2.00

__) 1 Light diffuser, drafting mylar$1.00/sheet, makes many0.01

__) 1Shutter wire, 3 " electric wire 12 to 16 gauge

__) 1Machine screw, #6 x 32 x  with nut ($1.60/100)@0.050.05

Equipment not included in kit.

Damping mechanism (can be attached to lever arm)

The Serial Box Interface (oscilloscope or other voltage measuring device)

The output can be connected directly to a computer and saved for analysis using a Serial Box Interface. A serial box interface is available for IBM or Mac computers and is capable of digitizing 50 samples a second at a 12 bit resolution. Supporting software is available from Vernier Software. Analysis may include measures of damping and free period. The circuit for this type of measurement puts a second resistor in series with the light sensitive resistor. A 6 volt source (actually anywhere from 1.5 to 9 volts) is placed across the circuit. The voltage at the center is recorded. Changes in the beam position affect the light reaching the sensor, causing a change in voltage proportional to the position of the beam.