Maker's Name: 
Griffin, London
Where made: 
10 × 10 × 24 cm

A thermocouple is a device that generates electrical energy from thermal energy. A linear thermopile, such as this museum piece, is a set of thermocouples connected in series that produce an electric current with a voltage that is the total of voltages produced by each thermocouple. Much like Boys’ Radio-micrometer, this device is used to measure the strength of light radiation by absorbing it and converting it to heat. When used on a light source that emits in the visible or infrared band of the electromagnetic spectrum, the device produces an electric current that can be measured by a galvanometer and in doing so, can measure the intensity of the light source.

The thermopile in this collection uses bars of bismuth and antimony in the thermocouples. Each alternating bar is shielded so as to let only half of the device receive the infrared radiation and produce a temperature difference. This setup is built on top of a circular brass base, with a height adjustable vertical brass casing that encloses the thermocouple bars. The vertical post ends with a hollow case with three windows, one of these windows having a shutter attachment. This shuttered window is the window used for letting in light for measurement.

The John J. Griffin & Sons company originally started in Glasgow as a joint venture between John Joseph Griffin and his brother. At first, they only sold and published books but soon expanded into the manufacture and distribution of scientific apparatuses, specifically for use in chemistry. This was due to John J. Griffin’s passion for chemistry. The company went through many mergers through the course of its life, becoming Griffin & Tatlock Ltd. in 1925, and then becoming Griffin & George Ltd. in 1954. Today, the company is known as Griffin Education, and is a part of Thermo Fisher Scientific.

This item is part of the UQ Physics Museum ‘Before Photonics’ Tour
< Previous Item | Return to Tour Menu | Next Item >