liggghts massflow/mesh group

Hi

I want to explicitly measure the mass of two different particles going through a face.

Simplified code

fix pts1 all particletemplate/sphere 15485863 atom_type 1 density constant 1380 radius constant 0.0037
fix pts2 all particletemplate/sphere 15485867 atom_type 1 density constant 115 radius constant 0.005
fix pdd1 all particledistribution/discrete 32452843 1 pts1 1.0
fix pdd2 all particledistribution/discrete 49979687 1 pts2 1.0


group group1 region reg
group group2 region reg


#particle insertion
fix ins1 group1 insert/stream seed 32452867 distributiontemplate pdd2 &
maxattempt 300 mass 10 massrate 0.476 overlapcheck yes vel constant 0. 0. -.5&
insertion_face inface extrude_length 0.1
fix ins2 group2 insert/stream seed 49979693 distributiontemplate pdd1 &
maxattempt 300 mass 10 massrate 0.476 overlapcheck yes vel constant 0. 0. -.5&
insertion_face infacegrain extrude_length 0.1


fix massbin1 group1 massflow/mesh mesh bin1 vec_side 0. 0. -1. count once screen no delete_atoms yes


variable time equal step*dt
variable massTotalBin1 equal f_massbin1[1]


fix outputCSV all print 2000 "${time},${massTotalBin1}" screen no file massMeasure.csv title "Time,massbin1"


If I change fix massbin1 group1 to fix massbin1 all I get output of measured mass.
Problem is it also counts the particles I do not want to track.