Serial No.AL2329 S82-1-13323
Rectifier type AC voltmeter, mirror scale, Industrial grade 1000 ohms/volt. Ranges 0-150, 0-300, 0-750V selected by 3 position switch Black bakelite case with leather handle. working, cover flap missing Enfield Middx England about 1960
These meters were industrial grade instruments used for testing the performance of electrical equipment. Mine was used originally used to determine the electrical efficiency of electric motors and similar to those that I used at University in the early 1960's.
Leighton has suggested that this voltmeter was probably from an earlier than I had thought as he has the dc version of the same meter with the dropdown flap still intact and fitted to the inside of the flap is a calibration certificate dated 1956.
I have recently been given a copy of "Wireless World" of November 1956 which describes this range of instruments:
The company was founded in 1921 under the name "British Sangamo " as the United Kingdom subsidiary of the "Sangamo Electric Co." of Springfield, Illinois, USA and initially manufactured integrating kilowatt hour meters and later expanded its activities to include industrial time switches.
In 1936 British Sangamo acquired the "Weston Electrical Instrument Co. " of Surbiton, Surrey. This company was the United Kingdom subsidiary of the "Weston Electrical Instrument Corporation", of Newark, New Jersey, USA, a company founded by Dr. Weston (a pioneer in the field of electrical measurements), and recognized as one of the worlds leading manufacturers of electrical measuring and associated equipment. The two companies were combined to form "Sangamo Weston ", which designed and manufactured a wide range of electrical measuring and control equipment.
Sangamo Weston became associated with products for the aviation industry and as a result, devoted its entire resources during the 1939-45 war, to the production of measuring instruments, indicators and associated ancillary equipment for use on aircraft. After World War 2 resources were put back into the original product lines but they continued to design and manufacture aircraft measuring instruments, indicators, measuring systems and associated equipment for customers all over the world.
In 1976 the Sangamo Weston Group was acquired by Schlumberger and became part of the Roxboro Group which disappeared into an (even larger?) group called "Dialight Corporation" in 2005.
I also have a Sangamo Weston timeswitch and as several people have asked about them I have provided some information about it see:timeswitch.html