Swinging Gate Seismometer

Collections · Geophysics Collection · Physics

Accession Number: 2015.ph.653

Description:

The seismometer is mounted on a metal base painted white, with three adjustable brass feet, and a sunken lip so that a large acrylic cover can fit over the instrument. Two brass dials sit outside the case lip.

Inside the encased area, the base is textured brass. A large black-painted metal scaffold supports an arm that extends lengthwise between two stainless steel brackets. The scaffold has two brass knobs, and two sets of brass squares, at the top and bottom. The plate between the brass knobs reads “1004”. On the bottom of the scaffold, two larger brass dials secure a piece of acrylic used to support a spool of copper wire which is mounted off of the scaffold. Attached to the copper wire are red-and-black covered electrical wires, attached to two black plastic knobs; these wires and knobs are not attached elsewhere and are very loose. This entire piece, with the copper wire, has been added to the instrument and was not part of the manufacturer’s model.

The black metal scaffold extends forwards to form a sort of arm, which supports two plates that are suspended between two metal brackets. Each bracket consists of a wedge-shaped black metal support with a brass tightening screw and two stainless steel blocks. The plate closer to the centre is plastic, with a thin metal foil on top and some kind of red centre. The plate closest to the edge is copper, supported by the thin arm and a metal-and-acrylic cylinder.

At one corner, there is a horizontal level tube willed with a clear fluid inside. There is also a builder’s plate made of brass.

Alternative Name: Seismometer

Primary Materials:

Brass, steel, copper, metal, plastic, glass, tape, fluid.

Markings:

“1004” is inscribed on the brass plate of the scaffold. One edge of the white metal base has “GPX. 7A” written in very faint marker. An “x” is scratched into the base as well. There are several pieces of masking tape on the instrument, and the manufacturer’s logo sticker is stuck to the plastic case.

Dimensions (cm):

Case: Height = 29.3, Width = 26, Length = 51.4; Instrument: Height = 27, Width = 29.2, Length = 56.8.

Function:

A seismometer continuously monitors ground motion. Its mechanism is based on a hinged gate. This instrument would have been placed on a sturdy pillar anchored to the ground. The seismometer system is sensitive to a particular frequency of motion. The movement of the instrument’s body relative to its massive hinged gate was detected using a magnetic transducer.

The signal would have been recorded using a galvanometer onto a rotating drum.

This instrument has been modified with added electrical component to simulate movement.

Condition:

Fair/Good: Critical components, including a delicate mechanical hinge, have been broken. The acrylic cover is in relatively poor condition.

Manufacturer: Sprengnether Instrument Co.

Provenance:

This artifact was acquired by the University of Toronto Scientific Instruments Collection on August 25th, 2014 from a storage room in the McLennan Physical Laboratory building.

Additional Information and References:

An audio interview with Gordon West (Jan 6, 2015) discusses this instrument. He identifies some damage to the object (broken hinge) and its probable cause and describes this seismometer as well as alternatives.

– St. Louis University Earthquake Centre. “Sprengnether horizontal seismometer.” Sprengnether Instruments. Last accessed February 3, 2015. Found at http://www.eas.slu.edu/eqc/eqc_history/SprengnetherInstruments/eqc_SprengInst.html.

Historical Notes:

The instrument was complicated and challenging to level and adjust. Newer instruments incorporate much stronger magnets and are consequently more sensitive.

  • Donated to UTSIC