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