Apparatus and process for measuring characteristics of particle flow

Apparatus for measuring characteristics of a particle flow, the apparatus comprising:

• a passage with an inlet and an outlet for guiding a sample flow comprising particles through the apparatus;
• means for electrically charging the particles;
• trapping means for trapping essentially all free ions and charged particles having particle diameter smaller than a trap cut-off diameter, the cut-off diameter being a particle diameter above which penetration through the trapping means essentially deviates from zero;
• means for measuring an electrical current carried by said charged particles that are not trapped;
• and
• control means for adjusting the trapping means to adjust the cut-off diameter based on measured electrical current carried by said charged particles that are not trapped,
• wherein the control means for adjusting the trapping means comprises means for adjusting the cut-off diameter to a reference cut-off diameter and to a measuring cut-off diameter resulting in a measured reference electrical current and a measured electrical current, respectively, carried by said charged particles that are not trapped, and
• wherein the means for adjusting the cut-off diameter is arranged to compare the measured reference electric current to the measured electric current, and to dynamically adjust the measuring cut-off diameter based on the comparison of the measured reference electrical current to the measured electrical current.

A process for measuring characteristics of a particle flow, comprising steps:

• a) guiding a sample flow comprising particles through a passage;
• b) electrically charging the particles;
• c) trapping essentially all free ions and charged particles having a particle diameter smaller than a trap cut-off diameter, the cut-off diameter being a particle diameter above which penetration through the trapping means essentially deviates from zero;
• d) measuring an electrical current carried by said charged particles that are not trapped;
• e) adjusting the trapping means to adjust the cut-off diameter based on the measured electrical current carried by said charged particles that are not trapped;
• f) adjusting the trapping means to adjust the cut-off diameter to a reference cut-off diameter and to a measuring cut-off diameter resulting in a measured reference electrical current and a measured electrical current, respectively, carried by said charged particles that are not trapped;
• g) comparing the measured reference electric current to the measured electrical current;
• h) dynamically adjusting the trapping means to adjust the measuring cut-off diameter based on the comparing of the measured reference electrical current to the measured electrical current;
• and
• i) adjusting the trapping means to adjust the cut-off diameter and alternate the cut-off diameter between a reference cut-off diameter and at least one measuring cut-off diameter to result in the measured reference electrical current and at least one measured electrical current, respectively, carried by said charged particles that are not trapped.

Apparatus for measuring characteristics of a particle flow comprising:

• a passage with an inlet and an outlet for guiding a sample flow comprising particles through the apparatus;
• means for electrically charging the particles;
• trapping means for trapping essentially all free ions and charged particles having a particle diameter smaller than a trap cut-off diameter, the cut-off diameter being the particle diameter above which penetration through the trapping means essentially deviates from zero;
• means for measuring an electrical current carried by said charged particles that are not trapped;
• and
• control means for adjusting the trapping means to adjust the cut-off diameter based on the measured electrical current carried by said charged particles that are not trapped,
• wherein the control means comprises means for adjusting the cut-off diameter to a reference cut-off diameter and to a measuring cut-off diameter resulting in a measured reference electrical current and a measured electrical current, respectively, carried by said charged particles that are not trapped,
• wherein the control means is further arranged to compare the measured reference electric current to the measured electric current, and to dynamically adjust the measuring cut-off diameter based on the comparison of the measured reference electrical current to the measured electrical current;
• wherein the trapping means comprise a voltage trap and the control means is further arranged to adjust a trap voltage of the voltage trap to a reference voltage and to a measuring voltage resulting in the measured reference electrical current and the measured electrical current, respectively, carried by said charged particles that are not trapped,
• wherein the control means is further arranged to dynamically adjust the measuring voltage based on the measured reference electrical current and the measured electrical current;
• wherein the control means is further arranged to adjust the trap voltage and alternate the trap voltage between a reference voltage and at least one measuring voltage resulting in the measured reference electrical current and at least one measured electrical current carried by said charged particles that are not trapped.