| Résumé | A circuit is described which allows precision measurements of the anode current of photomultipliers. In particular the circuit is suitable for the measurement of anode-current ratios which occur in spectrophotometry. In this circuit the principles of the potentiometer are utilized. Special features include a compensator for the dark-current, a choice of two sensitivity ranges, and the possibility of normalizing the higher of the two measured anode currents to unity. The precision obtainable depends greatly upon the particular photomultiplier employed. For an EMI 9558B the precision was found to be ±0.02%. Linearity measurements with photomultipliers were made. Considering the precision of the measurements no deviations from linearity were found. |
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