Wattmeter, 1970
1970
Kelvin astatic wattmeter
1901-1913
Irwin astatic wattmeter
1920-1926
Lord Kelvin astatic wattmeter, 0-200W.
Kelvin astatic wattmeter
1913-1920
Siemen's wattmeter No 1410 in case
Portable laboratory wattmeter
1956
Sumpner wattmeter
1904
Addenbrooke electrostatic wattmeter (ca 1904)
1904
Sumpner double gap wattmeter
Ferranti model MCBZ28 electric wattmeter
Ferranti model W wattmeter
Ferranti induction wattmeter
Radio Frequency Wattmeter
1943-1953
Portable Reflecting Wattmeter Model 5999 No.R578
1964
Sangamo Weston AC and DC wattmeter
1958
Ferranti Wattmeter
1942-1947
Ferranti Wattmeter
1920-1940
Induction type "F" single phase sector wattmeter
7 range clip-on wattmeter
Record induction wattmeter
Kelvin's astatic (electrodynamometer) wattmeter
1893-1900
Duddell-Mather standard wattmeter No.36
1903-1919
Portable precision dynamometer wattmeter serial no.1477ONW
1953
Sangamo Weston Ltd wattmeter
Ferranti model MCBZ28 electric wattmeter
Ferranti wattmeter
Electrodynamic multi-range Wattmeter No. 760592.
wattmeter
1950
Sumpner's portable standard volt- and wattmeter (an iron-cored electrodynamometer)
Moving coil galvanometer
1910
Single-phase portable a.c. and d.c. wattmeter
1926
Dynamometer wattmeter no.L79139
Low-loss electrodynamometer wattmeter
Irwin dynomometer wattmeter by the Cambridge Instrument Co. Ltd. No. L 24972
1930
Electrodynamometer wattmeter no.1263438 by Evershed and Vignoles Ltd
1950-1970
Inkwell graphic electrodynamic wattmeter
Drysdale-Tinsley polyphase wattmeter
AC wattmeter by Elliot Brothers
1927
Precision electrostatic wattmeter, Rayner and Paterson, 1913
1913