Foster Instrument Co. Ltd.
Letchworth, Herts. (1910)

Brand: Resilia

Founded in 1910, Foster Instrument Co.  focused on temperature measurement. Early on, pyrometers for industry and aircraft were key. Charles Foster, the founder, even dabbled in car transmissions with the "Autogear."

By 1926, they showcased innovative pyrometers: a 24-hour dial recorder with minimal vibration and an indicator with automatic signalling and broken-couple alarms.

Post-war, they solidified their reputation, offering various temperature measuring instruments. A 1960s catalogue highlighted their specialisation, with electrical resistance thermometers, thermo-electric pyrometers, radiation pyrometers, and disappearing filament pyrometers as their core products. In 1971, they merged with competitor Cambridge Instrument Co., forming Foster Cambridge.

Their independent journey ended in 1974 with a takeover by Brown Boveri. Despite this, Foster Instrument Co.’s legacy as a leader in temperature measurement for over 60 years remains.

Foster Instrument Co. Ltd.: A Legacy in Temperature Measurement (1910-1974)

Founded in 1910 by Charles Edwin Foster, a former chief draughtsman at Cambridge Scientific Instrument Co., Foster Instrument Co. Ltd. carved a niche in the field of temperature measurement for industry and research.

Early Years (1910-1920s): From Pyrometers to Autogear

• The company initially focused on pyrometers, instruments crucial for precise temperature control in manufacturing and the burgeoning aircraft industry. [1] Exhibitions in 1920 showcased their pyrometer expertise.
• Foster's innovative spirit extended beyond pyrometers. He invented the "Autogear," a variable friction transmission system for cars, in collaboration with A. E. Bowyer-Lowe of Bowyer-Lowe Co., Ltd. While commercially unsuccessful, it highlighted their interest in exploring new technologies. [2]

Innovation and Expansion (1926-1940s):

• Foster instruments continued to evolve. By 1926, they introduced a novel 24-hour dial recorder utilizing a "Resilia" spring system, a patented invention by Foster himself. This design minimized vibration and ensured accurate temperature recording.
• Pyrometers remained a mainstay, with Foster showcasing advanced features like automatic signalling and broken-couple alarms at exhibitions. Portable surface calorimeters also joined their product line, demonstrating their commitment to diverse temperature measurement solutions.

Post-War Recognition and Specialization (1947-1960s):

• Listed as an exhibitor at the 1947 British Industries Fair, Foster solidified their reputation as a leading manufacturer of temperature measurement equipment. Their offerings encompassed a wide range, including indicating, recording, controlling instruments, pyrometers, and resistance thermometers.
• A 1960s catalog reflects their specialization in temperature measurement. They emphasized their extensive experience built over five decades and a dedicated technical staff to address customer needs. Electrical resistance thermometers, thermo-electric pyrometers, radiation pyrometers, and disappearing filament pyrometers formed the core of their product line.

Pyrometer Prowess: A Glimpse from the 1926 Catalogue

The 1926 exhibition provides a fascinating glimpse into Foster's pyrometer expertise:

• Dial Pyrometer Recorder: This innovative instrument utilized a unique "chain of dots" recording method. A carbon paper sheet beneath a translucent chart allowed for continuous temperature monitoring over a 24-hour period. This design minimized space requirements and ensured dust-proof operation.
• Pyrometer Indicator with Automatic Signalling: This advanced pyrometer featured signal lamps that illuminated based on temperature. White indicated optimal temperature, red signalled overheating, and green signified an overly cool state. Additionally, a "broken-couple alarm" alerted operators to malfunctioning thermocouples, preventing potential damage. 

1960 Foster Instrument Co. Catalogue; Types of Instruments for Temperature Measurement

Specializing in electrical methods of temperature measurement, Foster Instrument Co. offered a range of instruments catering to diverse industrial and research needs.

Electrical Resistance Thermometers:

• Ideal for measuring temperatures from -240°C to 550°C.
• Likely utilized the principle of electrical resistance change with temperature fluctuations for accurate measurement.

Thermo-electric Pyrometers:

• Most versatile option, covering a wide range from -200°C to 1600°C.
• Employed the Seebeck effect, where a temperature difference between two dissimilar metals generates a voltage for measurement.

Total Radiation Pyrometers:

• Measured temperature based on the total thermal radiation emitted by a hot object.
• Functioned effectively from 500°C to 2000°C, suitable for high-temperature applications.

Optical Disappearing Filament Pyrometers:

• Measured temperature by matching the incandescence of a calibrated filament to the object's emitted radiation.
• Offered high accuracy for extremely high temperatures, ranging from 700°C to 3000°C.

Foster Instrument Co. positioned themselves as experts in the field, highlighting their extensive experience and technical staff dedicated to customer needs.

Legacy:

Despite the eventual takeover by Brown Boveri, Foster Instrument Co. Ltd.'s legacy endures. For over six decades, they were a prominent player in the evolution of temperature measurement technology, contributing advancements and establishing themselves as a trusted resource for industry 

[1] The Aeroplane Feb 21, 1917, Page 510.
[2] A-Z of Cars of the 1920s by Nick Baldwin. 1994. ISBN 1 870979 53 2