Galvanometer mirror

All currents that had to be measured were sent to a central measurement room in which many mirror galvanometers were situated on top of vibration-free columns that were separated from the foundations of the building. One should realize that the many announcements in the early literature of the liquefaction of specific gases pertained to not much more than a mist or a few drops Kamerlingh Onnes planned to make liquid gases by the gallon. A separate hydrogen liquefaction plant was located in a special room with a roof that could be blown off easily. 

Fig. 4.10. Schematic representation of the essential parts of a mirror galvanometer, used for detecting Brownian motion.

Fig. 4.11. The time variation of the reading on the scale of a mirror galvanometer.

Current Indicators.—The best form of current detector for accurate work is a suitably dan ied mirror galvanometer of high megohm sensi-tivity for approximate purposes, however, a simple pointer galvanometer... 

The variation of the temperature of the copper block K, relative to that of the block C, caused by the introduction of the substance, is determined by means of ten copper-constantan couples in series, the electro-motive force being measured by means of a Siemens and Halske millivoltmeter. As these instruments allow very accurate readings to be taken, using a lens if necessary, it was possible to employ one of them instead of a mirror galvanometer. 

On account of the resistance of the leads to the constantan wire and the fall in potential across the ammeter, the energy actually introduced into the calorimeter is only 0 387 gm.-cals. The E.M.F. of the thermo-couple was measured with the aid of a small Siemens mirror galvanometer by Dieselhorst without this excellent instrument, which comes to rest in a few seconds, and is of ample sensitivity, the investigation would have been much more difficult. In the galvanometer circuit (in addition to a 300 ohm resistance) was a standard ohm to which a Weston cell with 100,000 ohms in series could be connected for occasional determination of the sensitivity. On reversing the connection to the cell in this series of experiments a difference... 

Light source—mirror—photographic paper using either a drum, time base, or flat bed temperature base—mirror galvanometer. 

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