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Finnigan Mat Gmbh

Varian Mat Gmbh

Heinz Lerche

Horst Rache

Peter Komander

Reiner Wedde

An ion detection current conversion circuit includes a conversion amplifier coupled with a conversion resistor assembly for converting an ion detection current produced by an ion detector into an ion detection voltage, the conversion resistor assembly comprising a resistor having a high resistance and a capacitive compensation element, and a compensation voltage circuit for deriving a compensation voltage from the ion detection voltage and feeding the compensation voltage to the capacitive compensation element, the compensation voltage circuit comprising a variable resistor for adjusting the compensation voltage.

Spectrometer amplifier compensation

For calibrating mass spectrometers with a plurality of ion targets (1), especially Faraday targets, to which a separate measuring channel is assigned in each case, an electric current from a highly stable electrical voltage-source (6) is supplied, as a measurement reference-value, to the individual measuring channels, in chronological succession, via a resistor (R.sub.2) having a high degree of constancy. For this purpose, a control device (7) is provided, which actuates switching devices (K.sub.1 -K.sub.n) in such a manner that the correct chronological sequence is maintained. The calibrating measurement-values, obtained with the aid of this highly stable current, are intercorrelated in order to form a correction-value, this correlating operation being performed in a calibrating-correction unit (5). Several calibrating measurements, with different currents, can be carried out for each measuring channel (V.sub.1 -V.sub.m), and these measurements can also be carried out with the aid of an external, linearly controllable voltage-source, which produces these currents via the resistor (R.sub.2) having a high degree of constancy.

Process for calibrating ion-current amplifiers in mass spectrometers and

An integrating circuit comprises an integrating amplifier having an inverting input for receiving a signal to be integrated, and a feedback capacitor connected between the output of the amplifier and its inverting input. The output of the integrating amplifier is connected one input of a second amplifier having another input connected to zero potential. The output of the second amplifier is connected to a diode switching arrangement which is actuated between a conductive state in which a d.c. connection is established between the output of the second amplifier and the inverting input of the integrating amplifier and the feedback capacitor is forcibly discharged and a non-conductive state in which the d.c. connection is interrupted and the output of the second amplifier is connected to zero potential so as to enable the integrating amplifier to integrate the signal received by its inverting input.

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Bremen, Germany

Heinz Lerche