Edison electrolyte meter, c 1881.

Siemens and Halske watt-hour meter.

Safety matches and Avo Smethurst exposure meter, c 1930s.

Avo Smethurst Exposure Meter, c 1930s.

Throat strap containing sound sensor, 1999.

Watkins' Standard Exposure Meter, 1900.

Ayrton and Perry ammeters, late 19th century.

Steam recording meter from dynamometer Car

Biosensor from Oxford Biosensors, c 2006.

John William Rayleigh, British physicist, c 1910.

John William Rayleigh, British physicist, c 1900.

John William Rayleigh, British physicist, 1894.