Signedon dial: HB
on dial: Charles Engelhard / Hudson Terminal Buildings / 30 Church Street / New York
Inscribedon dial: D.R.P. [and] MADE IN GERMANY
base numbered: 894
FunctionA galvanometer is an instrument designed to measure the amount of electric current. This one was used with a pyrometer, such as 1998-1-0448.
A pyrometer is an instrument used for measuring the temperature of heat radiating substance. This measurement is based on the Stefan-Boltzmann law. Radiation heat would be focused on thermocouples found inside the pyrometer. These would produce a small electrical current picked up by the binding posts. That current would then be transmitted to a galvanometer such as this one. A reading of the electric current on the dial would directly give, from the second scale on this galvanometer, the temperature of the substance under study.
For a general discussion, go to the following website.
ProvenanceFrom the Engineering School, Harvard University.