Ω

Cambridge Instrument Standard Resistors

 

Cambridge Instrument Co. Ltd. This is one of ten such resistors that were given to me in 2011. They were originally in the test department of Honeywell Controls. I have:
2nr 1000Ω
2nr 1000Ω
2nr 100Ω
2nr 10Ω
2nr 1Ω
1nr 0.1Ω
1nr 0.01Ω

For four terminal resistors (such as this one) the resistance of the standard can be exactly defined as the voltage drop between the voltage terminals for unit current in and out of the current terminals.

Some interesting history (especially as it relates to other items in my collection)

The Company was originally formed in 1881 as The Cambridge Scientific Instrument Company by Horace Darwin Charles Darwin's youngest son, to supply the laboratories of Cambridge University.The Darwin family association continued until the 1970s. The firm started in Panton Street before moving to St Tibbs Row in 1882. It became a Limited Liability Company in 1895 when it moved to new larger premises in Carlyle Road. In 1920 the company took over the R. W. Paul Instrument Company of Muswell Hill London and the name changed to The Cambridge and Paul Instrument Company Ltd. The name was shortened to the Cambridge Instrument Co Ltd in 1924 when it was converted to a public company.

The company was sold to George Kent in 1968 and since the merger it was organised into four divisions, each being eventually separately sold off. Many ex-company employees either founded other well known companies or gained important positions in them. William T. Pye, who had joined as foreman in 1880 left in 1898 to form the W.G. Pye Instrument Company with his son, ultimately to branch out into Pye Radio. E. I. Everett joined with Edgecombe to form Everett Edgecome Ltd.