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Baseline restorer
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When a pulse passes through a capacitor the baseline must be suppressed slightly in order to make the net area of the pulse above and below the baseline equal. This is baseline shift and for a succession of pulses may be significant.

The MCA will measure the height of the pulse relative to a fixed voltage and so variations in the baseline to the pulse will cause errors in the measured pulse height.

  • To avoid baseline shift, such a baseline restorer circuit has as its main purpose the return to zero of the baseline between pulses in as short a time as possible.
  • The use of baseline restoration also greatly reduces the effects of low frequency disturbance such as power line hum and vibrational microphonics which may be sent along the signal.
  • The most effective type at high count rate is the gated restorer in which the baseline is maintained at ground potential during the period between pulses.

Baseline shift due to a regular series of identical pulses.  The total areas above and below the baseline are equal.


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1999, 2000 The University of Liverpool, Department of Physics

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