An inexpensive device for digital measurements of isotopic ratios

A typical double collecting mass spectrometer was greatly improved by the use of a device which enables automatic measurements of isotopic ratios in digital form to be carried out. The system consists of two electrometers with high value resistors being automatically replaced by capacitors for the ratio measurements. Thus noise produced by the resistors is eliminated. The electrometer output signals are digitised by a digital voltmeter, and the digits plus some additional information are transferred to a calculator printing the signals and their ratio. In this way the mass spectrometer MI-1305 was improved and a precision of 0.03 parts per thousand was reached. (author)