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