Patent ID: 8674761
Filing Date: 2014-03-18
Classification: G01L,H03F

Abstract:
1. Charge amplifier circuit for converting positive and negative charge signals Q that are output by a piezoelectric measuring element into a digital signal D that is proportional to the present measured value at the measuring element, comprising a charge amplifier V 1 having a charge input and a voltage output for converting the detected charge Q into a voltage U 2 , wherein a compensation circuit K comprising two outputs is connected downstream of the voltage output of the charge amplifier V 1 , wherein the first output is connected to the charge input of the charge amplifier V 1 and the second output to a counter Z having two inputs Z+, Z−, and wherein on the one hand, the compensation circuit K can produce a compensation charge Qk+ or Qk− respectively, that is proportional to the voltage U 2 and that can be sent to the charge input of the charge amplifier V 1 by means of the first output in order to compensate the input signal Q, and wherein on the other hand the compensation circuit can produce a number of pulses P+, P− that is proportional to the magnitude of each compensation charge Qk+ or Qk− produced, and said pulses can be sent to an input Z−, Z+ of the counter Z opposite the sign of the particular compensation charge Qk+ or Qk− by means of the second output, wherein the desired digital signal D, which is proportional to the sum of the charge quanta input beforehand, is available at the output of the counter Z.