Accession No

4965

Brief Description

Lucas Contact Breaker, by Cambridge Scientific Instrument Company Ltd., English, 1913

Origin

England; Cambridge

Maker

Cambridge Scientific Instrument Company Ltd.

Class

physiology; laboratory apparatus

Earliest Date

1913

Latest Date

1913

Inscription Date

Material

metal (steel, brass, iron, other)

Dimensions

length 525mm; width 410mm; length of steel spring 465mm

Special Collection

Provenance

Transferred from the Department of Physiology, University of Cambridge, on 23 January 1997.

Inscription

(on a plaque)
‘THE’
‘CAMBRIDGE SCIENTIFIC’
‘INSTRUMENTS CO. LTD.’
‘CAMBRIDGE ENGLAND
‘NO. 18449’

Description Notes

Lucas Contact Breaker, by Cambridge Scientific Instruments Co., English, 1913.

The contact breaker enables electrical circuits used in physiological experiments to be broken in succession at definite intervals of time. It may be used for investigating the refractory period of a nerve or muscle and many other experiments.

It consists of a loaded steel spring arranged to swing in a horizontal plane, and initially held by a catch at one end of its travel (swings in an arc). When the catch is released, the movement of the spring opens two electrical contacts in succession at definite time intervals, which may be adjusted by moving one of the contacts over a graduated scale, each division corresponds to a time interval of about 0.0003 second. Time interval between opening of the contacts may be varied from 0.0001 (or zero) to 0.3 second.

Black painted iron base cross bow shape. Arc of base is where the circuit break occurs. Catch for steel spring is mounted on a block at the right edge of the arc. From the left runs a scale in brass from 0 to 180, in intervals of 10. Scale finishes in the middle of the arc. At the middle point is mounted a fixed contact point which consists of a vertical bar with two terminals for electrical current to be applied, a retractable point on a small spring to enable the contact. Pivoting on top of the arm of the object, and terminating at the arc is the moveable contact point and a brass indicator that runs along the measuring scale. This contact point is constructed the same was as the other. The plaque with inscription as above is fixed to the moveable arm. The loaded spring of steel material is fixed at the back of the arm and extends along it to meet the fixed contact point, 465mm in length.

Complete

References

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