Signedon housing above window: Société Centrale de Produits Chimiques / No 44 rue des Écoles / Paris / Electromètre P. CURIE / No. 60
FunctionQuadrant electrometers are used for absolute measurements of electrostatic potentials. This quadrant electrometer was probably configured to measure the small currents associated with the ionization chambers used to measure radioactive samples. The electrometer's aluminum vane is housed within a four-chambered case and suspended by a fine wire with a small mirror attached so the vane and mirror are free to rotate. When current is introduced (e.g., from the ion chamber), since one pair of quadrants has a positive charge and the other pair has a negative charge (opposite quadrants are connected by a wire), the potential difference between the vane and the quadrants changes, causing the vane and mirror to turn. The magnitude of the deflection of the vane can then be measured using beam of light reflecting off the mirror onto a scale placed in front of the meter. The beam of light moves across the scale in conjunction with the changing current from the ion chamber and the associated changing potential difference between the vane and quadrants, and the time required to move across a specified number of divisions on the scale can be related to the sample's activity through calibration with a known source.
ProvenanceFrom the Department of Physics, Harvard University, 11/21/1956.
Related Workshttp://www.orau.org/ptp/collection/electrometers/quadrantelectrometer.htm