Serial No. L38841
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Cambridge Instruments Four decade Wheatstone resistance bridge with range switch enabling the instrument to be used over a very wide range from 11.11 ohm to 11.11 MΩ full-scale (0- 11.11kΩ with ratio X1) For measuring the higher resistance ranges a larger voltage supply is recommended. I have tested it against 1000Ω and 100Ω standard resistors and found it to be accurate down to the last digit.
I made a battery box from plywood complete with
terminals to take four "C" cells instead of the original 4.5 V 126
battery to slot into the clip on the inside of the lid. Since doing
this I have found that these batteries (or their modern replacement)
are still available see: http://www.cellpacksolutions.com
two pictures of one of the decade switches which indicate the quality
of the instrument.
This is one of many instruments collected by Jack Davidson C Eng FIEE which I have been given by Dr Graham Winbolt.